A manual for smallholder farmers in Sub-Saharan Africa with special focus on Ethiopia March 2025
Integrated Pest ManageMent for onIon cultIvatIon
A manual for smallholder farmers in Sub-Saharan Africa with special focus on Ethiopia
March 2025
This manual has been produced under the auspices of the project More bees: Supporting agrobiodiversity and livelihoods in Amhara, Ethiopia which was funded by the UK Government through Darwin Initiative 2022 to 2025.
This collaborative project responded to the urgent need, raised by beekeepers and farmers in Ethiopia, for farming practices which do not present risks to honey bees, people and the wider environment. The organisations listed here worked together, drawing on prior experiences and expertise, trialling new work in new locations and empowering farmers to learn about effective Integrated Pest Management approaches.
The Brighthelm Centre North Road Brighton, BN1 1YD, UK www.pan-uk.org
Images
Bees for Development Ethiopia Mulu Belew Building PO Box 0786 Bahir Dar, Ethiopia beesfordevelopmentethiopia.org
Bees for Development UK
1 Angel Court St. Mary’s Street Monmouth, NP25 3DB, UK www.beesfordevelopment.org
All images are copyrighted to the authors of the Manual unless stated otherwise.
Reproduction
You are welcome to translate and/or reproduce parts of this manual provided the purpose is for education and training, and not for commercial gain. Permission for reproduction is given on the understanding that Bees for Development, Pesticide Action Network UK and Pesticide Action Nexus Ethiopia are acknowledged with contact details provided in full.
This manual has been developed as the result of accumulated expertise and experience of growing onion using Integrated Pest Management approaches in Ethiopia. The information presented here has been tested together with farmers through Farmer Field School methodology. The objectives of these Farmer Field Schools have been to provide season long training on IPM so that farmers can:
@ Learn how to grow healthy crops
@ Make informed decisions about implementing crop management practices
@ Learn about the use of natural enemies for pest management – conserving them through habitat modification and the use of supplementary food spray
@ Become experts in implementing IPM and managing crops without using Highly Hazardous Pesticides
@ Record their costs of production using IPM and compare with conventionally managed crops
@ Integrate beekeeping enterprises within their farms, without exposing honey bees to risks caused by Highly Hazardous Pesticides
acknowledgeMents
This manual was produced by Pesticide Action Nexus Association Ethiopia, Pesticide Action Network UK, Bees for Development Ethiopia, and Bees for Development UK under the auspices of the project More bees: Supporting agrobiodiversity and livelihoods in Amhara, Ethiopia which was funded by the UK Government through Darwin Initiative. We thank the Darwin Initiative for their financial support and acknowledge Atalo Belay, Stephanie Williamson and Alex Stuart for their expertise and technical input. PAN Ethiopia’s IPM field work in the Central Rift Valley was conducted in partnership with PAN UK with financial support from Traid , and these experiences contributed greatly to the development of this manual, along with work from other parts of Ethiopia, and elsewhere in the world.
PESTICIDE ACTION NEXUS ASSOCIATION (PAN-Ethiopia)
PurPose of the Manual
Introduction
This manual draws on experiences of Integrated Pest Management (IPM) practices from multiple sources, including the Amhara and Oromia Regions in Ethiopia, where onion is widely produced by smallholder farmers and semicommercial farmers. The main objective of this manual is to provide guidance on IPM for onion cultivation.
who will use this manual?
The manual will be useful for onion producer farmers, development agents who work at the grassroots level with farmers, agriculture experts, trainers and facilitators at different levels, and others who are interested in sustainable approaches to pest management.
how to use this manual
This onion IPM manual is a technical reference guide for farmers and development agents about how to implement IPM for onion production. It gives background information, studies and practical exercises that can be implemented by onion farmers and by development agents during field-based trainings, via farmer field school (FFS) approaches and other farmer learning groups.
Agroecological farming, including IPM, cannot be implemented as an ‘off-the-shelf’ package and needs adaptation based on local contexts. The manual includes technical guides throughout the crop life cycle and gives ideas on how to implement major IPM practices through discovery-based IPM implementation and training.
The field, which includes different biotic and abiotic factors and their interactions, is the best space for farmers to trial, discover and learn about the impact of these interactions on their crops.
INTEGRATED PEST MANAGEMENT FOR ONION CULTIVATION
A manual for smallholder farmers in Sub-Saharan Africa with special focus on Ethiopia March 2025
PESTICIDE ACTION NEXUS ASSOCIATION (PAN-Ethiopia)
1. IntroductIon
Agriculture constitutes the principal source of income and employment for the majority of the population in Ethiopia. It is the leading sector in the national economy, accounting for about 46% of GDP, while contributing almost 90% of export earnings and employing 85% of the population1
Vegetables are among the major crops grown by commercial, semi-commercial and smallholder farmers, both for domestic consumption and as a source of cash income. Onion is one of the most economically important vegetable crops produced by smallholder farmers in Ethiopia. The land area under onion production is increasing, mainly due to its high profitability per unit area, ease of production, and the increase in small-scale irrigation schemes in the country2. Onions are produced both under rain fed conditions in the rainy season and via irrigation during the dry season, but much of the production occurs during the dry season, under irrigation3. Irrigated production in the Ethiopian context typically starts following the end of the long rainy season which runs from June – September.
Onion (Allium cepa) is a vegetable grown worldwide for its bulbs. It is one of the most important dry season vegetables cultivated in Ethiopia. Onion is largely grown by smallholder farmers but semi-commercial farmers and a few commercial growers are involved in the production under irrigation schemes.
Onion is produced by farmers as a food source and as a source of cash income. Farmers earn money by selling onion seeds, bulbs and seedlings. It is among the most preferred and widely produced vegetables by smallholder farmers in Ethiopia. This is mainly because of ease of cultivation and low risk of loss and damage when produced, harvested and transported at scale. Compared to other vegetables, onion withstands rough handling until final delivery to consumers. When properly stored, dry onion bulbs can be stored for 2-3 months4,19 after harvesting, which reduces the risk of loss and provides marketing opportunities for famers.
Onions grow best on well-drained sandy loam soil with high organic matter content. The optimum altitude range for onion production is between 700 and 2200 m.a.s.l. with an optimum growing temperature between 15 – 23 °C5
Like other crops, onion production in Ethiopia faces challenges that compromise yield and profitability. Soil health and plant protection are among the main factors affecting onion yield and profitability, of which plant protection is the main focus of this manual. Pests and diseases pose production challenges and farmers use chemical pesticides as their sole pest management option, leading to many health and environmental harms. Most of the pesticides used by smallholder farmers in Ethiopia are Highly Hazardous Pesticides (HHPs). The main objective of this manual is to provide guidance on different pest management methods and how those methods can be integrated to reduce the use of pesticides and their negative impacts while maintaining farmers’ livelihoods.
2. Integrated Pest ManageMent (IPM)
Integrated Pest Management (IPM) combines different management strategies and practices to grow and protect healthy crops by minimizing the use of pesticides. It is a decision-making process where growers consider the pests, the crop and weather conditions to help them implement an appropriate management method or a combination of methods. It should not be limited to scouting for a certain density of pests in a crop before automatically reaching for pesticides. Rather, it should consider the range of pest management approaches available to farmers and it emphasizes the prevention of pest outbreaks, not only reacting to them. IPM emphasises the growth of a healthy crop with the least possible disruption to agroecosystems and encourages natural pest control mechanisms6.
IPM can be used to manage pests in a cost-effective way, whilst minimising hazards to people, non-target organisms including beneficial insects, and the wider environment.
The aim of IPM is not the complete elimination of pests. It is to keep or reduce the pest population below the level which causes economic damage, which is best achieved by supporting and augmenting natural control mechanisms rather than replacing them with pesticides. It requires a good understanding of the agroecosystem, pests and their natural enemies, the crop and its life cycle. It requires farmers to develop their skills of monitoring the crops, pests and natural enemies to assist them in better decision-making.
Effective IPM should be based on the principles and concepts of agroecology7 to optimise interactions between plants, animals, humans, and the environment8. Unlike pesticide-intensive systems, agroecology does not consist of one set of defined practices. Rather, the basic approach of agroecology is to work with nature and farmers’ needs, to select and adapt the practices to fit into the local context9. Elements could include 1) providing favourable soil conditions to improve crop health and reduce susceptibility to pests, and 2) promoting biodiversity to provide living space for natural enemies.
Rather than relying on synthetic pesticides to control pests, agroecological farming nurtures biological systems that do the job for us. Experiences of agroecological IPM implemented by smallholder onion farmers in Ethiopia showed that they were able to reduce pesticide spray frequencies by more than 70% for onion production after going through one season of skills based IPM training10 (see Annex 2).
components of IPM
Different management methods including cultural, biological, physical and chemical methods can be integrated into an IPM approach. IPM has five basic components as shown in Fig. 1.
Figure 1. IPM components and a summary of key concepts included.
table 1. IPM components and practices associated with the five IPM basic components (Adapted from 11).
growIng a healthy croP PreventIon of Pests and dIseases
9 Understanding how a healthy crop can reduce the need for pesticide use
9 Overall crop health
9 Improving soil health
9 Choice of variety and seed, and seedling quality
9 Good sowing practices
9 Understanding which practices help or hinder pests and diseases
9 Crop rotation and intercrops (including refuge crops and border strips)
9 Agronomic timing
9 Weed management
9 Field hygiene
9 Reducing fungicide use
harnessIng benefIcIal organIsMs
9 Awareness of natural enemies of cotton pests
9 Providing habitat for beneficial organisms
9 Reducing insecticide use
fIeld observatIon and decIsIonMakIng use of bIologIcal and PhysIcal treatMents
9 Field observation to monitor levels of pests, diseases, weeds and natural enemies
9 Decision-making on spraying
9 Understanding how pests/ diseases can develop resistance to insecticides/ fungicides and ways to avoid this
9 Knowledge of when and how to apply nonchemical controls
9 Use of bio pesticides, botanicals, trapping or other non-chemical controls as treatments
Figure 2. IPM farmer learning day at Enguti, Amhara, Ethiopia.
3. growIng a healthy croP
3.1. raising healthy seedlings
There are more than 10 onion varieties cultivated in Ethiopia. The Ethiopian Institute of Agricultural Research (EIAR) breeds and releases improved onion varieties to growers. Adama Red, Bombay Red, Nasik Red and Nafis are among the commonly grown onion varieties in Ethiopia
There are three different sources of onion seeds in Ethiopia (i) imported seed (ii) seeds produced from research centres and reaching the market through agriculture offices and local agriculture input retail shops (iii) farmer managed seeds – onion seeds produced by farmers and sold directly to onion farmers or through the local agriculture input retail shops. Onion seed production serves as one of the income generating activities for smallholder farmers. Apart from individual smallholder farmers, a number of farmer cooperatives are involved in onion seed production12.
Smallholder farmers prepare their own seedlings or buy from other smallholder farmers who grow onion seedlings as an income source. Farmers establish onion seedling nurseries either (i) in their backyards or (ii) in their farm. They need a water source for irrigating the nursery.
Below are some important tips for establishing an onion seedling nursery:
Site selection: Select a place where there is adequate water source for irrigation. Do not use a plot which was used for onion seedling production or onion production in the previous season. This crop rotation practice will help reduce disease incidences which may arise from pathogens remaining in the soil from the previous season.
Seedbed preparation: Prepare the land before making seedbeds. Add well decomposed compost about two weeks before preparing seedbeds and sowing onion. This will give time for the compost to be well mixed with the soil and increase soil fertility. Growing healthy plants, one of the IPM principles, starts with healthy and well-nourished onion seedlings.
Preparing the bed: Once the soil is prepared well, with the addition of organic matter (manure, compost), prepare a raised bed for sowing the onion seeds. The beds should not be more than 1 metre wide for ease of management purposes – including weeding, watering and spraying when needed. The length of the bed can be any length and depends on what is suitable for the grower. The raised bed has to be flat (see Fig. 4).
Sowing: Prepare lines along the length of the bed that are 5-10 cm apart for sowing the seeds. Onion seeds are small in size and it is important to make sure that the holes are not too deep, as it will prevent germination – about 1 cm deep is enough for proper germination. After sowing, cover the seeds with light soil and then mulch the whole bed with straw/grass which should be removed after about a week from seedling emergence. If the mulch is left in-situ for too long this can cause the seedlings to bend as they grow, and should be avoided. The mulch will help preserve water and increase the soil temperature and will facilitate germination.
Figure 3. Commonly grown onion varieties in EthiopiaAdama Red (top) and Bombay Red
Watering: Water the seeds repeatedly (check the moisture) in the first 5-10 days, so that the seeds can get adequate moisture for germination.
Seedling management: After seedling emergence, remove the mulch and continue carefully watering the seedlings. Follow up and remove the weeds (if any), regularly monitor for pests. Disease may occur when the seedling grows, and an application of a diluted concentration of baking soda (see baking soda recipe preparation procedures below) is recommended to prevent the disease from spreading.
Hardening off: Onion seedling will be ready for transplanting at about 45-60 days old. A week before transplanting, reduce watering and apply fertilizers to harden off the seedlings. This will help the seedlings to get stronger to withstand the harsh conditions once transplanted to the main field.
Examples of good practices:
9 buy only healthy-looking seedlings
9 keep seedlings healthy at nursery stage, if growing own seedlings
9 discard any diseased or poor appearance seedlings at transplanting
9 keep seedling roots covered, away from sun and wind before and during transplanting
9 do not transplant in midday sun
9 take care not to damage seedlings at transplanting and irrigate the next day after transplanting
9 when hoeing and weeding young seedlings, take care not to damage seedlings
Figure 4. Raised bed prepared for onion seedling production.
table 2. Summary table showing most important activities in life cycle of onion production
growth stage duratIon of the growth stage (approx. number of days)
Land preparation
Seedling stage 30
Vegetative growth 30
Bulb formation 30
Bulb thickening 45
Maturation 15
Harvesting
Post-harvest
Yield and economics
notes
Prepare the land properly with 3-4 rounds of plough, ridge preparation.
Manage seedlings properly while on the seedbed to ensure well-established onion seedlings. Plant protection and soil fertility management are key while on the seedbed.
New leaves start to grow and the onion neck starts to appear, proper weed management is needed. Plant protection practices should also be put in place to manage major onion pests like thrips.
Bulb development starts, lower old leaves will fall, the onion reaches its maximum growth.
Bulb size increases and becomes visible, lower old leaves will continue to dry out.
Plant neck reduces in size, bulb development reaches to its final stage, leaves lay down on the ground.
Onion harvesting, grading (separation of marketable and unmarketable bulbs).
Management of crop residues.
Recording yield, calculating production costs, total sale and net profits.
Source: PAN Ethiopia Vegetable IPM curriculum
3.2. land preparation and soil health management
Prior to transplanting, land preparation should be done by ploughing the plot 3-4 times to remove debris and soil clods. Onion performs well in a plot with a good amount of organic matter. During land preparation adding farmyard manure, conventional compost and vermicompost is recommended. Compost and farmyard manure should be added about two weeks before transplanting, during ploughing, so that it can be mixed well with the soil.
@ Apply vermicompost as side-dressing during growing season: this needs to be done during the first and second cultivation before the onion starts bulb development
@ Sow a green manure (e.g. lupine, grass pea) to cover soil in the off-season
Figure 6. Land preparation with oxen ploughing, and cleaning debris from the plot.
3.3. transplanting
Onion seedlings can be ready for transplanting when they are about 45-60 days old. In Ethiopia, the recommended spacing for most onion varieties is 40 cm between ridges, 20 cm between planting rows and 5 cm between plants (see Fig. 7). The plot has to be pre-irrigated a day before transplanting. Smallholder onion growers generally use furrow irrigation with the ridges prepared before transplanting. In areas where the soil is sandy and the daily temperature is high, farmers use closed ridge system to conserve water.
3.4. nutrient management
Adding organic manure, including compost and farmyard manure, is highly recommended, as onion responds well to organic manure. Adding 25 – 40 metric tons per ha is recommended to ensure good quality and volume of onion harvest.
Urea and nitrogen, phosphorus and sulfur (NPS) are the widely used synthetic fertilizers in Ethiopia. Farmers use these fertilizers for onion production at different times (i) during transplanting – NPS (ii) as a dressing during first and second hoeing – usually 15-20 days after transplanting and 30-40 days after transplanting respectively – with split application. Application of urea as a dressing should be completed before the onion starts bulb formation. The recommended rate of NPS and urea per ha for onion is 200 kg and 100 kg respectively. Urea is applied in split application – with the first split applied 15-20 days after transplanting and usually done when farmers do the first hoeing. The second split is applied 30-45 days after onion transplanting.
Figure 7. Spacing between ridges, between rows and between plants of newly transplanted onion.
box 1. PreParatIon and aPPlIcatIon of verMIcoMPost
Simply speaking, vermicompost is earthworm excrement, called worm castings. Vermicomposting is the process by which worms are used to convert organic materials (usually wastes) into a humus-like material known as vermicompost. The goal is to process the material as quickly and efficiently as possible. It is a type of composting in which certain species of earthworms are used to enhance the process of organic waste conversion and produce a better end-product. Various species of worms are used, usually red wigglers (Eisenia fetida or Eisenia andrei), white worms, and other earthworms. Vermicomposting experts recommend using red wigglers because of the rate they consume compostable materials and their fast breeding nature. Earthworms feed on the organic waste materials and pass it through their digestive system, producing a granular excretion which is known as vermicompost.
why vermicompost?
Vermicomposting is faster than conventional composting which is done in backyards and gardens by burying organic wastes, because the composting process is facilitated by the worms. Researchers have also shown that nutrients from vermicompost are also relatively easier for plants to absorb13. These facts make vermicomposting preferable.
Benefits of vermicompost
Studies have shown that vermicompost contains higher percentages of both macro and micronutrients, compared to conventional compost. It can improve biological, chemical, and physical properties of the soil. The chemical secretions in the earthworm’s digestive tract help break down soil and organic matter, so the castings contain more nutrients that are immediately available to plants. It can enhance plant growth, suppress disease in plants, increases porosity and microbial activity in the soil, and improve water retention and aeration. Vermicompost also benefits the environment by reducing the need for chemical fertilizers.
In the Central Rift Valley of Ethiopia, Ziway/Batu area – farmers used vermicomposting as a soil conditioner, adding it a week before transplanting onion or other vegetables, adding as a side dressing during cultivation. It has helped to gradually reduce their use of synthetic fertilizers.
how can it be done?
Vermicomposting can be done by using different methods depending on the labour and financial capacity and the volume of compost needed. The preparation methods may vary from the ones listed below if they are suitable for the worms, maintain moisture, and are suitable for management. Farmers may use one of the methods and the selection depends on access to the materials, space needed and ease of constructing the facility.
9 Heap method: farmers can prepare vermicomposting unit on the ground with some protection.
9 Pit method: pits of 50-60 cm depth can be prepared on the ground with protection in the pit to prevent worms from escaping and moisture retention purposes.
9 Raised bed: the easiest method for smallholder farmers is to prepare a wooden bed – using locally available materials with 1 m height, 50 cm width and the length can vary depending on the capacity of the farmer and need. Figure 8 below shows the raised bed made by farmers.
Materials needed for vermicomposting: A wide range of agricultural residues, such as straw, husk, leaves, and stalks, weeds. etc. can be used as inputs for vermicomposting and converted into vermicompost. Other potential inputs for vermicompost production are livestock waste, poultry litter, dairy waste, food processing waste, etc. With the use of these inputs and one of the methods mentioned above, vermicomposting can be easily done.
Cautions: When adding compostable materials to the vermicomposting facility, we need to avoid adding non-compostable materials like glasses, metals, plastics and fatty food wastes. It is also advisable to put a covering mesh to protect the worms from birds and other animals that may feed on them. To maintain the temperature, sprinkle water intermittently and arrange the vermicomposting under a shade to protect it from the sun and rain.
Usage: Vermicompost can be used for all crop types. Depending on the crop types and size of the field, application can be done either by broadcasting or adding the compost around the base of the plants during cultivation. For onion, farmers can apply vermicompost during first and second round cultivation as a side dressing. Different studies show that rate per ha for different crops ranges between 5 – 10 tons of vermicompost.
Figure 8 A typical raised bed for vermicomposting – constructed by smallholder farmers.
3.5. water requirement
Water requirement of crops can vary depending on the local weather condition, soil type, the way they are cultivated and the stage of development. For example, the soil type and weather in Ziway area, Oromia, is different from Fogera and Mecha areas, Amhara. Onion grown in the sandy soil and high daily temperature in Ziway area may require more water than the onion grown in the Mecha and Fogera areas which have red and black clay soils.
Onion is a crop that requires a significant amount of water, especially during its bulb formation and development stages. Flooding and farrow irrigation are the two mostly used irrigation methods by smallholder onion farmers in Ethiopia. Furrow irrigation is preferable over flooding for water conservation and soil erosion prevention (Fig. 9). In furrow irrigation, furrows are prepared along the onion rows and water is channeled through the ridge which then allows onions to slowly soak up or get moisture. This plays a significant role in reducing disease incidents compared to the flood irrigation method. To reduce evaporation and achieve optimal efficiency, conducting irrigation in the morning or late afternoon is recommended.
Irrigation involves regular monitoring of soil moisture, as this can help avoid over irrigation. Excessive irrigation can cause waterlogging, increase soil salinity and then reduce crop yield.
Actions that can help improve onion irrigation:
@ Plant onion in rows – using double rows following the recommended spacing (see section 3.3)
@ Assess if irrigation is needed by checking soil moisture (‘dig 10cm and squeeze’ test – see section 4.1.1)
@ Prepare short (not more than 4 metres) and closed ridges (rings) – this helps conserve water
@ Irrigate onion in the morning (before 10 am) or in the afternoon (after 5 pm)
@ Properly irrigate onion in the early development stages (i.e. in the first 60 days) as this is key to ensure good bulb enlargement
@ Reduce irrigation once the onion is mature
Figure 9. Pre-transplanting irrigation of an onion plot with furrows.
Over-irrigating is a common practice by smallholder onion farmers. “Plants like human beings don’t want to drink too much water”. Hence, farmers need to follow up water requirements and conduct irrigation. Failing to do so and overirrigating can cause disadvantages including:
@ Water lodging affects the onion yield and creates problems in bulb formation
@ Onion disease – mainly damping off
@ Delayed maturation
@ Reduced bulb size – shifting energy to the vegetative growth and producing too much unmarketable bulb
@ Nutrient leaching – essential nutrients will leach down creating nutrient deficiency on the crop
@ Contributes to soil degradation and water contamination
@ Too much irrigation is costly
3.6 weed management
Onions are shallow and weak-rooted plants and infestation by aggressive weeds can severely reduce yield. Weeds may compete with the onion crops, taking water, nutrients, growing space or sunlight (shading out the onion) leaving the onions to perform badly. Weeding onion plots should be done in the early stages of the weeds, before their root system develops and affects the onion. Based on experiences in Ziway and Fogera areas, a first-round weeding should be done about two weeks after transplanting. This helps farmers easily remove weeds before they reach to a level that can cause root damage to the onion. Onion plants infested with weeds will show stunted growth and poor performance in vegetative growth which is then reflected in the final yield (see Fig. 10).
Figure 10. Onion plot highly infested with weeds, and onion plants showing poor performance in vegetative growth.
For good weed management farmers need to know:
@ When the onion crop is vulnerable to competition from weeds
@ When and how to carry out cost-effective weed management
@ How to make use of weeded materials
Knowing the most vulnerable stage of the crop: Newly transplanted onion seedlings have to adapt to a new environment and develop a new root system in the first two weeks after transplanting. These young and newly transplanted onion seedlings cannot compete well with other plants. Proper weed management is needed during the following onion stages:
@ Seedling establishment – first two weeks after transplanting
@ Vegetative growth
@ Bulb initiation
How to do onion weeding: Weeding can be done manually either by pulling weeds alone or along with hoeing (cultivation). To protect the delicate and web like onion roots from damage, smallholder farmers use finger hoes to pick weeds and conduct hoeing at the same time.
Make practical use of weed resources: It is good IPM practice to leave collected weeds in the field to decompose and return their nutrients to the soil. This is an important agroecological practice which helps close the nutrient cycle. Farmers can also pile collected weeds at the field edge, to turn into compost.
Figure 11. Finger hoes as used in Ethiopia.
4. ProtectIng the croP
Plant protection is one of the strategic inputs for crop production. There are several plant protection approaches that can be used to tackle damaging pest and disease infestations. Management of pests and diseases can be done using either a single management method or a combination of different methods, depending on the nature of the pest or disease, the crop type, growth stage and environmental factors.
Pest management methods can be:
@ Cultural: This management method involves proper implementation of agronomic practices and managing the crop habitat to disfavour pest and disease infestation. For insect pests, practices in the cultural management method create unfavourable conditions and interrupt the lifecycle of insects. Cultural methods are the basis of an IPM programme. Examples of cultural pest management methods include; proper land preparation, postharvest management of crop wastes, field sanitation/hygiene, intercropping, crop rotation, and furrowing, solarisation, adjustment of irrigation time, hoeing and weed removal.
@ Physical: These management methods involve practices that prevent pests from coming into contact with the crop and/or practices that prevent male and female insects from mating and producing offspring. The use of odour-based traps (behavioural methods), insect traps, hand picking, netting, are some examples of physical methods. Yellow sticky traps for onion thrips are a good example of the physical management method.
@ Biological: This method mainly involves encouraging and conserving natural enemies of pests (predators and parasitoids) for pest management purposes. An important practice to conserve natural enemies is to avoid both calendar-based spraying and broad-spectrum insecticides. Another practice is to provide food and space for natural enemies by increasing habitat diversity. A good example of conservation biological control is sowing alfalfa or leaving hedgerows in-between blocks of onion plots to provide a refuge place for natural enemies. Another example is the use of the food spray method14 to attract natural enemies of pests into farmers’ fields. Onion farmers in Ziway, Central Rift Valley of Ethiopia, use these practices to conserve and encourage natural enemies (see Fig. 12).
Figure 12. Alfalfa strips planted between blocks of onion plots to increase refuge and access for natural enemies.
@ Botanicals: Botanicals (plant extracts) can be used for pest management in different crops including onions. They can be used as a component of IPM and are effective in preventing a build-up of pests and help farmers reduce pesticide use. Extracts from neem seed and mixtures of garlic, ginger, onion and chilli are among the botanicals used by onion farmers in Ziway. These extracts are used together with the food spray method for the management of sucking pests in onion and other vegetables. See Boxes 2 and 3 below for the extraction and application procedures of two recipes.
@ Chemical: Chemical control refers to the use of synthetic pesticides. The use of pesticides is recommended only as last resort – i.e. after exhausting all other available management methods, when action thresholds are exceeded and pest infestation continue to increase, despite the use of the other management methods. Pesticides, particularly Highly Hazardous Pesticides (HHPs), cause environmental degradation, biodiversity loss and human health problems. It is important to select the least harmful pesticides and only use them as a last resort.
@ Integrated Pest Management: IPM is based on the integrated use of all management methods available –cultural, physical, biological and as a last resort, chemical control. The concept of IPM is often presented as a pyramid, with the greatest focus on cultural approaches to prevent the development of infestations (shown as the foundation of the pyramid) 15. Management methods in the middle of the pyramid should then be applied, but they are only likely to be effective in combination with other approaches. The least focus should be on chemical pesticides which should only be applied as a measure of last resort.
Figure 13. Pyramid of IPM techniques (Source: Collier, R. 2023).
4.1. Insect pest management
Damage caused by insect pests is one of the factors affecting crop production. Pests cause a reduction in crop quality and quantity – affecting the overall productivity and profitability of farmers.
Pests such as onion thrips, leaf miner and onion fly, affect onion. Onion thrips (Thrips tabaci) is the most destructive insect pest of onions in Ethiopia.
Thrips tabaci (onion thrips)
description
Onion thrips are tiny insects that range from creamy yellow to brown in colour. They have a needle like mouthpart, which they use to tear open plant cells to feed on plant juices. They frequent and feed on the newly emerging onion leaves - deep between the leaf blades. Hot and dry weather favours thrips population build up, while their population could go down with heavy rain. The hot and dry weather in Ziway, Fogera and other onion producing areas in Ethiopia favours thrips populations. They overwinter in crop resides, in alfalfa, wheat, weeds in the farm and along crop field borders.
damage symptoms
Onion plants attacked by thrips have silver lines, which may change to white patches. Under severe attack, the entire plant may appear to be silvery and, in the end, onion leaves will curl and twist. Such damage on the onion leaves reduces the photosynthetic capacity of the plant leading to slow growth, which then reduces bulb size – affecting yield. A severe thrips infestation can cause the entire plant to die and cause yield loss.
Tips for observation: Silvery lines or patches, white patches and curling leaves are common symptoms that farmers and field workers need to look for when conducting monitoring. Observe in-between the leaf blades – down in the newly emerging leaves.
4.1.1. Prevention
Cultural, physical, biological and chemical methods are available for the management of onion thrips. Using a single management method is not advisable and a combination of different methods is best. Depending on the local situation (weather, diversity in the agroecosystem etc.), crop growth stage and insect population, farmers can make decisions to select or combine management measures. The following cultural methods are recommended to reduce plant susceptibility to onion thrips and prevent the pest population from building up.
cultural management recommendations:
@ Apply proper and timely irrigation: If onion plants are water-stressed they are more susceptible to thrips attack. Irrigate only when the soil is dry 10 cm below the surface and no rain is forecasted. Conduct the soil squeeze test to make irrigation decisions. Dig and take a handful of soil about 10 cm below the surface and squeeze with hands. If the soil holds together and forms a ball, then it has moisture and can wait a few days for irrigation. If the soil falls apart, it is dry and needs irrigation. Farmers do need to be mindful that different soils perform differently to the squeeze test and so experience is important here.
@ Nitrogen management: Avoid excessive application of nitrogen fertilizer on onions as this has been shown to increase thrips numbers due to increased susceptibility and attractiveness of the crop16
@ Crop waste management: Conduct good field sanitation at the end of the season to avoid thrips overwintering.
@ Intercropping: Plant alternate rows of onion with carrots, lettuce, peppers, tomato, spinach etc. - plants that are not in the same family with onion.
@ Rogue out plants that are heavily infested with thrips.
@ Crop rotation.
4.1.2. Harnessing Beneficial Organisms
Thrips have a number of natural enemies including lacewings, ladybird beetles, minute pirate bugs, hoverfly larvae, predator thrips, and parasitic wasps which can help regulate their population. Farmers can enhance the role of biological control (natural enemies) by avoiding broad-spectrum insecticide use, modifying the crop habitat and using supplementary food spray. Food spray can be applied starting at early onion growth stage, ideally a week after transplanting, to attract natural enemies into the onion field.
Methods to promote natural enemies:
9 sowing habitat strips including alfalfa and other flowering plants
9 improving field margin habitat for natural enemies
9 using green manures
9 avoiding insecticide use in the first 7 – 15 days after transplanting
9 using food spray
using the food spray method to increase natural control of pests
what does the food spray method involve?
Beneficial insects known as natural enemies play a very important role in helping to keep pest levels under control. The food spray method increases naturally occurring biological control of pests by encouraging more natural enemies into farmers’ fields. This is achieved by three, linked components:
A. manipulating the crop habitat to provide a more attractive environment for natural enemies
B. spraying the crop foliage with a food supplement (the ‘food spray’) to attract natural enemies
C. avoiding use of synthetic insecticides, which will disrupt or kill natural enemies
A. Providing more habitat: A field of bare soil with only small seedlings does not provide an inviting home for many natural enemy groups to shelter from sun and rain, and to breed. It will not contain many of their food source prey in the first few weeks of crop growth. By sowing 1-2 rows of alfalfa, lablab or other beans with dense vegetative growth between every 8-10 rows, or blocks of onion, or as field borders, farmers can provide a habitat which will attract natural enemies (Fig. 14).
Figure 14. Onion field trial plot with alfalfa borders for natural enemies.
B. The food spray supplement: Food sprays for natural enemies can be made from waste brewers’ yeast or partly fermented maize. The ingredients when sprayed as a solution onto foliage give off a powerful odour which insects can detect from up to 400 metres away. Food spray ingredients attract mainly predatory natural enemies, including ladybirds and other predatory beetles, lacewings, hoverflies and predatory bugs. These natural enemies ‘home in’ on the odour, thinking that it is coming from their usual plant-feeding prey, such as aphids. Once in the crop, they start searching for small, soft-bodied prey items and then consume them, performing the pest control service that the farmer wants.
C. Protecting natural enemies from harmful insecticides: Many of the insecticides available in Ethiopia (especially the cheaper, older ones) are more toxic to natural enemies than to the pests they are aimed at controlling. Farmers are often unaware of this huge disadvantage of commonly used insecticides. Using the food spray method therefore goes hand-in-hand with awareness-raising and training farmers to select less toxic, preferably non-chemical, alternatives as part of IPM strategies.
What are the benefits of using this method?
@ An active population of natural enemies can keep early season sucking pests (such as aphids, leafhoppers, mealybugs and whiteflies) from reaching problematic levels.
@ Without natural enemies, major pests like bollworm become more difficult and more expensive to tackle with synthetic chemicals alone.
@ Relying on synthetic chemicals soon becomes unproductive, as pests can rapidly develop resistance to the chemicals, forcing the farmer to spray more often.
@ Taking advantage of natural pest control helps farmers to reduce use of hazardous insecticides and avoid harm to human health, wildlife and the environment.
@ Many vegetable consumers, including farmers themselves, are concerned about the health impacts of hazardous pesticides used by farmers and want to buy safer, more sustainable products.
@ Farmers can often save money by shifting from chemical to biological control, while maintaining, or even improving, crop yield and quality.
@ Smallholders who cannot afford to buy pesticides can increase their yield and income by making use of natural enemies, at very low cost.
when should food sprays be applied?
The aim of the first food spray of the season is to bring natural enemies into the crop so they are ‘ready and waiting’ BEFORE the first pests start to arrive. In onion, it is recommended to apply the food spray a week after transplanting.
After the first food spray application, regularly monitor the pests and natural enemies and apply the food spray when the balance between predator insects and pest insects becomes unfavourable. Experiences of using food spray in onion production in Ziway area shows that as long as there is at least one predator for every two pests in the field, balance is favourable. With this favourable balance, natural enemies can keep pests under control- at least for the next few days.
To find out what the current ‘Predator: Pest’ balance is, farmers need to monitor their fields at least every week. It is best to monitor early in the morning before 10.00 am as natural enemies will hide during the hottest part of the day.
Experience of the onion trials in Ziway showed that food spray needs top up spray treatment with neem and other botanicals when the population of thrips builds up, before going into another management method.
box 2. food sPray PreParatIon
Ingredients and preparation of maize based food spray
@ Maize kernels: maize seeds
@ Sugar: adding sugar as a food spray ingredient helps to keep predatory insects within the sprayed field. It provides temporary, high energy food source for a few days if prey numbers (pests) drop
@ Household solid soap: added as a sticking agent. Soap contains salts and fatty acids and can act as a selective pesticide for small, soft-bodied insects, e.g. thrips, aphids, spider mites, and their eggs
Preparation procedures
Preparing the maize based food spray product
@ Prepare clean maize; 8 kg for 1 ha worth of spray
@ Boil 10-15 litres of water separately per 4 kg batch of maize
@ Add boiling water to maize in a bucket and soak for 24 hours
@ Use a sieve or fine mesh cloth to separate the soaked maize from the water
@ Crush and grind the soaked maize kernels using a hand-powered mortar or other equipment
@ Add 8-10 litres cold water to the crushed maize and leave for 48 hours
@ Filter out the crushed kernels using a sieve, then dry the solid mass in the sun. This will yield about 4 kg of dried, crushed maize. This is then ready for spray solution preparation. This can be kept up to 30 days
Preparation of solution for spraying – solution preparation using 1 kg of the food spray
@ Take 1 kg of the food spray product and mix it with 5 litres of water and wait for 48 hours – until it ferments well and produces odour
@ Filter it out and add 250 g sugar and 50 g household soap – cut it into pieces and mix it well in the solution. Filter this out and the solution is ready
@ Add 25 litres of water and spray
From the 4 kg dried maize based food spray, it is possible to get 100 litres of food spray solution.
Ingredients and preparation of yeast based food spray
@ Waste brewer’s yeast
@ Sugar
@ Soap
Preparation procedures
@ Take 1 litre waste brewer’s yeast and mix it with 5 litres of water
@ Keep it for 48 hours to ferment until it creates an odour
@ Filter it out and add 250 g sugar and 50 g household soap – cut it into pieces and mix it well in the solution. Filter this out and the solution is ready
@ Add 25 litres of water and spray
@ Use this ratio to prepare additional solution that can cover the whole farm
Figure 15.
Maize crushing as part of the food spray preparation process.
how decisions are made based on the balance observed?
Scenario A: More natural enemies than pests. DECISION: There is no need for food spray treatments, or any additional pest control, at least until the next monitoring time
Scenario B: Pest numbers are more than double the numbers of natural enemies. The pests are winning and more biological control is needed! DECISION: Apply food spray within the next 2-3 days, to bring more predators into the crop. At this stage, a top up with neem or garlic, ginger, onion and chilli pepper (GGOC) extracts, can be used.
Scenario C: Equal numbers of pests and natural enemies. Within the ‘healthy balance’ level BUT which will increase next – pests or predators? DECISION: Re-check the crop within 3 days to see what the trend is and then make a final decision.
Scenario D: More pests than predators but still within the ‘healthy balance’ level. DECISION: Look at damage symptoms and loss levels in the crop to help make the best informed decision and re-check the crop very soon. Farmers can apply botanicals to bring the pest population down.
4.1.3. observation and decision-making
Regular monitoring is vital to follow changes in the thrips population as this will help make management decisions before infestation reaches a level that causes economic damage. Look closely (using hand lenses is recommended – if available) between the leaf blades at the newly growing onion leaves where the creamy yellow nymphs and brown adults may be found. Bulb initiation (about 2-3 weeks after transplanting), and bulb thickening stages are the most critical growth stages, when the onion needs the most energy, and regular monitoring 1-2 times per week is vital. Pest attack during these periods will cause the most serious loss in yield. The Ethiopian Ministry of Agriculture recommends taking action when thrips numbers reach 5-10 per plant, and has identified a range of management methods, along with different approaches to decision-making for onion thrips management (see Table 3).
Table 3.
Onion thrips management methods and decision-making approaches17 (adapted from CABI, 2015).
@ Destroy crop residues and plough fields after harvesting to eliminate resting sites of the pest
@ Avoid planting onion crops in the same field continuously to avoid thrip re-infestation
@ Prepare soil well before transplanting onions to encourage fast and healthy growth
@ Use pest-free seedlings
@ Intercrop onion with carrot or cabbage as trap crops
@ Remove weeds that may harbour thrips within and around the field
@ Use recommended spacing and fertiliser rates
@ Scout regularly, starting when plants are at 4-5 leaf stage, check spaces between newly emerged leaves, stem and inner neck of onions for signs of the pest
@ Look for feeding signs such as white or silvery leaf spots, streaks or patches on the leaves
@ Use yellow, blue or white sticky trap to monitor and sample pale yellow immature and brown adults
@ Scout at least five plants in ten different parts of the field and edges (where adults infest first)
@ Take action when thrips numbers reaches 5 to 10 per plant
Direct, non-chemical methods:
@ Mulch with straw to provide shelter for thrips predators, thereby reducing thrips populations
@ Use sprinkler irrigation to reduce thrips population, if possible.
Biopesticides:
@ Botanicals or other non-synthetics: Neem seed preparations or azadirachtin product (e.g. Nimbicidine)
@ Garlic, Ginger, Onion and chili paste – extracts
Synthetic insecticides:
@ Spinetoram products
@ Spinosad
The above pesticides have a low risk to humans but are highly toxic to bees and use should be minimised.
Source: CABI Plantwise.
4.1.4.
use of biological and Physical Methods
botanicals
Plant extracts such as neem seed, neem leaf, GGOC paste etc. can be effectively used against thrips. Application of neem and GGOC extracts before or at the first sign of thrips infestation is effective in preventing the pest population from building up. Experiences of onion growers in Ziway showed that spraying neem seed extract about 5-7 days after transplanting prevents thrips population build up for two weeks. This was one of the factors which helped them reduce pesticide spray frequency. Box 3. below shows detailed preparation procedures of neem seed and GGOC paste extracts.
box 3. PreParatIon of extracts froM ggoc Paste
Preparation of a paste from the four ingredients is the primary step of the extraction. Hence, take the following amounts from each of the ingredients:
• ½ kg garlic
• ½ kg ginger
• ½ kg onion
• ¼ kg chilli pepper
Once the inputs are ready, crush them together using a machine or a manual mortar and make a paste. Mix this paste in 4-5 litres of lukewarm water and keep the solution for one day. Filter it after one day and use the solution to spray the crops. The filtrate can be used as a fertilizer – add it on the farm.
Preparation for application
After filtering, 2-3 litres of extracted solution will be ready for dilution and spray. When preparing to spray it is important to consider the crop stage as this determines the required concentration. If the crop is at a small stage especially for leafy greens, concentration should be pre-tested on a spot treatment to avoid phytotoxicity.
at the small stage of the crop:
• Take 250 ml GGOC extract
• Mix it in 15 litres of water and spray on the crop
• If more volume of the solution is required, use the same rate to mix and spray as the crop grows:
• Increase the GGOC volume to 2 fold
• Mix it with 15 litres of water and spray shelf life and storage:
• The GGOC extract can be stored for 2-4 months but for better results use the extract in 1 month from the date of preparation
• The solution should be stored under shade
Spray time: To reduce the possibility of leaf scorches, it is recommended that farmers spray in the morning before 10 am or in the afternoon – after 5 pm.
Note: Before spraying the whole farm, it is recommended for farmers to do a concentration test on a few plants at least one day before treatment. It is also highly advisable to do pest scouting before making a decision to spray the whole farm. This is mainly because farmers can do spot treatments where there is high infestation to save time, energy and resources.
box 4. neeM seed extract recIPe and PreParatIon
Ingredients: Neem seeds, water, sugar and soap. The neem seeds can be pre-collected, dried and thoroughly crushed/powdered using manual mortar with a mill.
@ Take 1 kg neem powder, mix it with 5 litres of water in a bucket and wait 24-48 hours (waiting time can be reduced to 12 hours if the extract is urgently needed).
@ Filter out the solution; the solid part can be used as a fertilizer on the farm.
@ Dilute the solution with 20-25 litres of water, add 250 g sugar, 50 g household soap, mix well, filter and spray on the crop. The soap is needed to help stick the neem solution to the crop foliage.
Note: Stir very well and filter the solution before pouring into the knapsack sprayer.
Apply normally, in the same way as any conventional insecticide. Make sure to get good coverage of the onion leaf, especially in between the leaves – where thrips frequent.
synthetic insecticides
Insecticides are widely used by most onion grower farmers in Ethiopia due to their ease of use and knockdown effects on the pest. Repeated spray frequency is needed when insecticides are used as sole management option for thrips. This will then cause adverse effects on non-target organisms like bees and other beneficial insects, lead to the development of pesticide resistance and biodiversity loss. Insecticides, hence, should only be used in combination with the aforementioned management methods as a last resort. If necessary, selection of only less hazardous insecticides should be applied, such as spinosad and spinetoram. However, these are highly toxic to honey bees, thus they should be applied very early in the morning before bees are actively foraging, or very late in the afternoon.
4.2. disease management
Diseases are among the most important yield reducing factors for onion production. The most commonly occurring disease types affecting onion production in Ethiopia include downy mildew, purple blotch, damping off, rust, white rot, anthracnose, etc. Downy mildew and purple blotch cause significant yield losses in smallholder onion production in Ethiopia. Disease management strategies that can apply for all onion diseases, and decision-making guidance for the most common onion diseases are given below. These are practical actions that can be implemented by onion farmers in different agroecological zones in Ethiopia.
4.2.1
Prevention
Prevention is the best approach for onion disease management. It is better than relying on direct control methods, through fungicide sprays. Implementing cultural practices (see list below) can prevent the occurrence and spread of onion disease. Onion diseases like warm and moist weather, as high humidity allows fungal and arterial diseases to reproduce rapidly. Customising cultivation practices like irrigation, fertilizer application, management of crop residues and crop rotation can play a significant role in reducing disease incidence.
Preventative control actions recommended for onion diseases:
@ Good post-harvest clean-up, removing infected material from field.
@ Good land preparation and site selection and crop rotation (do not plant the same crop or family in a field previously sown to that crop, especially if disease problems were serious).
@ Careful selection of suitable crop/variety for the season and site.
@ Careful selection of healthy seedlings.
@ Correct spacing of plants to avoid overcrowding and poor air circulation.
@ Good transplanting methods (reduce stress on seedlings as much as possible, don’t expose roots to sun or wind, avoid hottest time of day, irrigate immediately afterwards).
@ Good agronomic practices, avoiding excess soil moisture.
@ Avoid damage to onion roots and developing bulbs during hoeing.
4.2.2. observation and decision-making
Observation and decision-making for crop disease management is a process by which growers regularly monitor the crop’s status through careful observation, collecting relevant data including disease symptoms, incidence/level, weather condition and general crop agroecosystem to make informed decisions about management. Knowing what is happening in and around the crop is essential to optimise management methods before the disease incidence reaches a level that causes serious economic damage.
downy Mildew
Downy mildew is an onion disease caused by a fungus. It is prevalent in areas with high humidity. High doses of fertilizers and high irrigation levels increase severity of the disease. Symptoms include formation of lesions near the tips of the older leaves, the leaf tips shrink, turn pale brown and later die18 (see Fig. 16). The downy mildew pathogen overwinters in infected crop residue, and in soil, as resistant spore-structures. It is also possible for the pathogen to be carried with the seed. Crop rotation and the use of diseasefree seed are important in preventing severe disease outbreak. Table 3 below shows decision-making procedures and the use of non-chemical preventive methods for downy mildew management.
Figure 16. Symptoms of downy mildew on onion leaves - early infestation and foliar decline symptoms (Photo credit: Howard F. Schwartz, Colorado State University, Bugwood.org).
Table 4. Decision-making procedures and management methods for downy mildew in onion crops (Practices in italics derived from relevant CABI PlantWise decision guidance sheets)
Preventative measures from PlantWise decision guide
Step 1
At first sign of affected plants
- 3 season crop rotation with non-onion families
- Select varieties tolerant of purple blotch, if available
- Use seedlings from certified seed
- Avoid planting in poorly draining fields
- Plant at recommended spacing 30 x 8 cm to allow air circulation
- Remove weeds at land preparation, especially weeds in onion family, plus any volunteer onions
Step 2
If incidence continues to increase, after Step 1 actions, by up to 10%
Step 3
If incidence continues to increase, after Step 2 actions, by over 10%
Remove infected leaves Rogue out badly affected plants
Improve drainage, especially if rainy conditions continue
Cultivate to aerate soil
Avoid working in field when foliage is wet
Avoid excessive nitrogen application
Remove infected leaves Continue suitable cultural practices Apply garlic extract or baking powder
Step 4
If incidence still continues to increase
Consider a suitable fungicide for this disease
CABI PlantWise advice is to start spraying as soon as first symptoms appear or first rainy period BUT under IPM we think try sanitation, cultural + non-chemical methods first
Make a further fungicide application but at least 7 days after last spray
CABI PlantWise advice is every 7-14 days, depending on weather conditions
downy MIldew
decIsIon trIgger sanItatIon cultural PractIces non-cheMIcal treatMent fungIcIde sPray
Purple blotch
Purple blotch is another economically important onion disease caused by a fungus. It is an important disease in warm, humid onion-growing regions of Ethiopia. The disease creates small white spots on the onion foliage. It often begins on older leaves as small, sunken, water-soaked lesions with light centres. Under moist conditions, the spots rapidly increase to large purplish blotches, often surrounded by a yellow to orange border. The lesions extend to girdle the leaf which leads to its collapse. The infection may spread to the bulb, where it may cause a wet, orange rot starting at the neck19 (see Fig. 17).
Implementing careful cultural practices can help reduce purple blotch incidence, such as using disease free seeds, keeping proper plant spacing, conducting regular weeding and ensuring proper air circulation to avoid moisture/dew on the leaves. Avoiding the use of excessive nitrogen and using crop rotation, good drainage and field sanitation are additional cultural practices that can help reduce purple blotch infestation. Table 5 below shows decision-making procedures and the use of non-chemical preventive methods for downy mildew management.
Figure 17. Symptoms of purple blotch on the leaf and neck region of an onion plant (Photo credit: CABI PlantWise).
table 5. Decision-making procedures and management methods for purple blotch in onion crops (Practices in italics derived from relevant CABI PlantWise decision guidance sheets)
PurPle blotch
Preventative measures from PlantWise decision guide
-3 season crop rotation with non-onion families
-Select varieties tolerant of purple blotch, if available
-Use seedlings from certified seed
-Remove weeds at land preparation, especially weeds in onion family
Step 1 At first sign of attack Remove infected plant parts Good cultural practices and careful seedling selection should avoid this disease becoming problematic
Step 2
If incidence continues to increase
Step 3
If incidence increases further
4.2.3. use of homemade recipes
Sprays used for downy mildew should also control any purple blotch present
CABI PlantWise guides advice is to repeat sprays every 14 days to a maximum of 3-4 per season
Farmers can use different homemade recipes and extracts to minimize onion disease infestation and spread. Experiences of onion growers in Ziway area showed that farmers can use dishwashing soap solutions, vermiwash/ vermi-team (an extract from vermicompost), garlic extracts and baking solutions as preventive sprays. Onion farmers in Fogera district also use a soap solution to reduce disease infestation levels before they go into fungicide treatments. Preparation of these homemade recipes do not require sophisticated materials and can easily be prepared by farmers at home. Preparation and application of bicarbonates is given below as an example.
bicarbonate salts for disease management
Sodium, potassium or ammonium bicarbonates have long been used for disease management by home gardeners and to some extent in the organic sector. These compounds have fungicidal properties when used as spray on diseased plants and also serve as a protectant from disease-causing pathogens. Both bicarbonates are more frequently recommended for control of powdery, rather than downy, mildews. Pesticide regulators in some countries have approved potassium bicarbonate formulated and registered as a horticultural fungicide.
Sodium bicarbonate (also known as baking powder) and potassium bicarbonate work against disease spread by making the foliage surface more alkaline. Mildew spores will only germinate when the pH level is neutral (pH 7) or slightly acidic (pH 5-6). Applying baking powder raises the pH level to 9.
More recently, potassium and ammonium bicarbonates have been promoted as less likely to scorch or burn plants than sodium, which can reach harmful levels on leaf surfaces, especially if not applied with some form of horticultural or cooking oil as an emulsifier to spread the compounds evenly over the foliage surface. Ammonium and potassium bicarbonates also have the advantage of providing nitrogen and potassium as plant nutrients. When applying any bicarbonates, it is important to avoid spraying in midday heat and full sunlight conditions as the bicarbonate salts may cause some leaf burn. Spraying early in the morning is recommended to prevent this risk.
Sodium bicarbonate diluted with water will not be very effective unless we add stickers and spreaders because the powder granules will be easily washed off with a little amount of rain and will not leave enough residue to have effect on the spores. Vegetable oils and soap can both act as stickers and spreaders. For oils, they are normally insoluble in water unless we add emulsifiers. However, a small amount of soap in the water solution will help stick and spread the baking soda. Most recipes for sodium bicarbonate solution include soap and/or some form of vegetable oil.
box 5. PreParIng hoMe-Made bakIng soda solutIon
Recipe for a 16 litre knapsack sprayer:
Mix 4 tablespoons of baking powder (approx. 112 g) with 4 tablespoons oil (approx. 60 ml) and add 16 litres water. Add 4 tablespoons liquid soap (approx. 60 ml). Stir again thoroughly before spraying.
Amount used for one round of spray for typical 0.25 ha (2,500 m2) plot:
1 kg baking powder
275 ml vegetable oil (= 18 tablespoons)
275 ml liquid detergent (= 18 tablespoons)
Cost: approx. ETB 611 / $4.6 USD per round (incl. oil and soap)
Ingredients for the baking soda solution works out more expensive than mancozeb but considerably cheaper than most other fungicides commonly used in Ziway, e.g. Ridomil Gold, Altracol or copper products.
Application:
Apply early in the morning or avoid the hottest time of the day and intense sunlight.
Make sure to apply a good coverage over the crop foliage, especially the leaf undersides where mildew diseases infect and reproduce.
Further applications may be needed within 7-14 days, if weather conditions favour the disease spread.
synthetic fungicides
When the disease incidences are high and are beyond the level that can be managed with homemade recipes and other cultural practices, farmers may use synthetic fungicides as a last resort. Decision to use synthetic fungicides needs to be supported with data from regular observations. This will help farmers to pick the right type of product available in the market. See the decision-making tables above for details on how to use fungicides when the need arises.
5. harvestIng and Post-harvest ManageMent PractIces
Harvesting can be done 120–145 days after transplanting depending on the variety. Onions are ready for harvest when the leaves collapse and their necks bend over. The top leaves will start to dry up when the onion is ready for harvest20. Under dry weather, onions can be dried in the field for a few days (see Fig. 18). Bulb uprooting can be done by hand. If harvesting is done before the necks bend, the bulbs many not be stored for long time. On the other hand, onion should be harvested before the necks are completely dry to avoid bulb rotting.
After onion harvesting, the leaves can be collected and be used for compost preparation purposes. The compost made from onion leaves should be used for crops which are not in the same family with onion to avoid possible pest and disease infestations.
Figure 18. Onion stored in the field for curing after uprooting and farmers cutting the bulbs.
6. record
keePIng
Record keeping is important for farming in general and for IPM in particular as it can help farmers track their farm activities and their associated costs. Farm records can also help farmers in decision-making and planning. Record keeping is an important aspect in enhancing IPM adoption. Farmers can keep detailed records of expenditures for different farm activities and then calculate the net profit per unit area. This helps them see differences in production costs between conventional and IPM methods.
Smallholder farmers in Ethiopia are not used to keeping farm records. With a project in Central and Southern Rift Valley of Ethiopia, PAN Ethiopia has been motivating farmers to keep costs of farm activities, total sale and then calculate net profits. This has been instrumental in motivating farmers to adopt IPM methods as they were able to see the final net profits of both IPM and conventionally managed vegetable plots.
The record keeping template given in Annex 1 can help farmers keep records of farm activities for onion production. The template included activities that are commonly implemented throughout the onion life cycle. Additional activities (if any) and their associated costs can be included in each of the sections.
Figure 19. IPM farmers recording their field observations in Ethiopia.
annex 1. Onion farmers’ field record book for costs and profits
ProfIle
Name:
Kebele:
Growing season:
Size of onion field this season:
onIon seed/seedlIng used
Sourced from?
Variety?
Treated or untreated seed?
Costs of nursery management (if own seedling is prepared)
How many kg? (nursery beds, if seedling)
Price per kg? or per bed if seedlings are used?
COST A:
Total cost of seed/seedlings used
PreParIng the onIon fIeld
Clearing the field
Ploughing
Manure or compost
Add up all the total costs for field preparation COST B: Field Preparation
transPlantIng
Date planted? _________________________________________ Plant spacing? __________________________________________
How many beds of onion seedlings are used? Record bed size
Seedling transportation
Pre-transplanting irrigation?
Transplanting
Add up all the total costs for transplanting COST C: Transplanting
weedIng
Weeding
Hoeing
Add up all the total costs for weeding/hoeing COST D: Weeding/Hoeing
IrrIgatIon
Add up all the total costs for irrigation COST E: Irrigation
Plant ProtectIon: food sPray and other Pest ManageMent costs
Food sprays
Neem seed sprays
Chemicals (pesticides, fungicides)
Add up all the total costs for plant protection COST F: Plant protection costs
onIon harvestIng
Onion uprooting
Bulb cutting
Packing and loading
Transportation
nuMber of workers hIred? daIly rate (cost Per Person)? total cost
Add up all the total costs for picking
Cost G: Harvesting
total ProductIon cost
COST A: Total cost of seed/seedlings used
COST B: Field preparation
COST C: Transplanting
COST D: Weeding/hoeing
COST E: Irrigation
COST F: Plant protection costs
Cost G: Harvesting
TOTAL Production Costs (Y)
sales revenue
descrIPtIon
Marketable yield
Price per kg
Total kg multiplied by per kg price
Sales revenue (Box X)
net IncoMe froM onIon harvest
Sales revenue (Box Y)
Total production costs (Box X)
Subtract Total Production Costs from Sales revenue
Net income (Box Z)
aMount harvested In kg
annex 2. case study of agroecological IPM in lake Ziway area
background
In 2018, PAN Ethiopia and PAN UK initiated an IPM research and farmer training project in Lake Ziway area, Oromia, Ethiopia with funding provided by the JJ Charitable Trust and the Dutch Sustainable Trade Initiative (IDH). The aim of the project was to reduce pesticide use and consequent health and environmental impacts by promoting agroecological IPM methods among vegetable farmers through Farmer Field Schools (FFS) and farmer-participatory learning plots.
A baseline survey of 75 smallholder onion farmers and 15 casual farm workers from five villages near Batu Town, revealed that 64% of the pesticides used by farmers contained Highly Hazardous Pesticides (HHPs). The frequency of pesticide applications ranged from 12 to 22 applications per season, with no field monitoring for pests or diseases, nor consideration of IPM principles. Alarmingly, 20% of smallholders and 73% of farm workers reported pesticide poisoning incidents in the previous year.
IPM field trials
To enhance the biological control of vegetable pests, the food spray method that had been successful in cotton (Mensah 2002a), was adapted by conducting formal field trials with the participation of relevant government and extension stakeholders. In particular, the project assessed the use of food sprays with vegetation strips that serve as refuges for natural enemies to help keep the insect population in check in the vegetable plots.
Based on positive field trial results, the methods were then incorporated into the FFS learning plots to assess their feasibility in farmers’ fields and whether farmers were willing to adopt such innovations. Table 6 lists IPM methods that were promoted via the FFS learning plots as part of an IPM approach for onion cultivation.
results from IPM learner plots
Comparisons between FFS IPM practices learner plots and traditional Farmers’ Practices (FP) plots showed significant reductions in insecticide use without compromising yield or income. On average over three seasons, there was a 76% reduction in pesticide spray frequency and 8% reduction in production costs in the IPM plots, with a slight yield increase and a 9% rise in net income. Initial uptake assessments showed that 92% of trained farmers adopted at least one IPM method, with practices like sanitary pruning and avoiding over-irrigation commonly mentioned.
adoption and uptake of IPM
Since the start of the project (and with further funding by Traid), over 700 farmers have now been trained in onion IPM via season-long FFS, averaging 11 weekly sessions, plus a further 500 farmers have been trained via peer mentoring. Specific efforts made to invite women along with their husbands, along with a gender awareness workshop with government staff, helped to recruit 33% women to FFS training. From a survey of 78 trained farmers in 2021, many farmers had significantly reduced their use of HHPs, with only 5.5% reporting acute health incidents compared to 20% recorded at the baseline. Of these surveyed farmers, 85% reported they still apply food spray and sow habitat strips of alfalfa or maize, while 60% of farmers reported they avoid HHP insecticides harmful to natural enemies and 60% leave natural vegetation/weeds in around fields for natural enemies.
table 6. IPM methods introduced to onion farmers in Ziway district
Method
and coMMents
Habitat borders Alfalfa borders to maintain natural enemies.
Food spray
Decision support
Wider spacing of plants
Application of neem seed extract
Avoiding HHP insecticides harmful to natural enemies
Applying vermicompost at transplanting and/or as a side dressing in mid-season
Assessing need for irrigation by checking soil moisture
Roguing (hand pulling) of individual wilt or virus affected plants
Sanitary pruning of badly diseased and older and yellowing tomato leaves
Application of baking powder solution (sodium bicarbonate)
Thorough clean-up of all crop waste after harvest and removal from field
conclusion
Brewery yeast-based food spray applied on crop foliage approx. 2-6 times per season to attract natural enemies into sprayed vegetable fields.
Simple counting method for monitoring levels of pests and natural enemies (take action when pest levels rise above 1 predator to every 2 pests). Actions include: a further food spray (either alone or mixed with neem); neem only spray; insecticide as last resort.
Mainly a disease management method and to enable farmer and workers to move more easily through the crop for better monitoring and better targeting of any applications.
Added with a food spray or as a stand-alone application if pest numbers are outstripping natural enemy control (i.e., when predator to prey ratio considerably < 1:2).
Many insecticides are broad spectrum and kill natural enemies or interfere with their performance. Only using insecticides as a last resort and selecting those such as spinosad, which are somewhat less harmful to natural enemies helps protect the natural enemies attracted with the food spray method.
Helps grow a healthier, more robust crop better able to withstand pest attack and reduce volumes of synthetic fertiliser needed.
Helps conserve soil moisture and can reduce drought stress in plants.
Using finger test of soil ‘stickability’ at 5cm deep. Reduces unnecessary irrigation and therefore duration of wet soil surface and humidity in crop canopy.
Removes infective material from the field and reduces risk of disease spread.
Reduces level of disease spores able to spread to clean tissue.
Opens up lower crop canopy for better air circulation and reduces humid microclimate which favours disease.
Makes the foliage surface less favourable for disease spore germination.
Reduces survival of pests which pupate or shelter as adults in crop waste. Crop waste can be composted, buried or fed to livestock or vermicompost units.
Overall, the results, combined with feedback from participating farmers and government extension agents demonstrated and provided confidence that agroecological IPM practices for onion cultivation in Ethiopia can match or exceed conventional farming yields, while promoting better health and environmental outcomes.
annex 3.
Further uptake across Ethiopia: Case study of an IPM field trial in fogera, amhara region
Due to the success achieved in Lake Ziway area, similar IPM training via FFS have since been conducted in other parts of Ethiopia, including Fogera and Mecha districts near Bahir Dar, Amhara. Since April 2022, Bees for Development-UK and Ethiopia and PAN UK and Ethiopia have been implementing the Darwin supported More Bees project in Mecha and Fogera districts in Amhara region. This project aimed at reducing the use of toxic pesticides by replacing them with alternatives, mainly ecologically based pest management techniques to reduce the adverse impacts of pesticides on honey bees, solitary bees and other beneficial insects, human beings, wider biodiversity and the environment.
Under this project, IPM methods were trialled and compared with the farmer-managed systems. The trials adapted the food spray method, and included the following three components:
• Sowing border crops/plants to harbour natural enemies: rows of Lablab (Lablab purpureus) plants were sown in and around the onion plots to create a welcoming environment for beneficial insects. Its foliage provides rich habitat for predatory insects like ladybird beetles, lacewings, hoverflies and parasitoids which feed on soft bodied sucking pests and small stage caterpillars of lepidopteran pests.
• Application of food spray.
• Avoiding the use of broad-spectrum insecticides – replacing them with plant extracts such as neem. If using pesticides is necessary, using IPM friendly pesticides is recommended.
In 2023, the trial on the use of IPM methods for onion production was conducted in Quhar Michael and Quhar Abo villages in Fogera district. The trials included comparison plots, called farmer practice plots, that were fully managed by a smallholder farmers.
In Quhar Michael village, the farmer in the farmer practice plot applied pesticides 16 times (with 4 rounds of insecticides and 12 rounds of fungicides). In the IPM plot, a total of 8 spray applications were made, with only 1 round of insecticide and no fungicide use. Baking soda was used as a preventive spray for disease while food spray neem extract and Nimbecidine were used for insect pest management. The pesticide spray frequency was reduced by 94% in the IPM plot compared to the farmer practice plot.
In Quhar Abo village, the farmer in the farmer practice plot applied pesticides 13 times (with eight rounds of insecticides and five rounds of fungicides). In the IPM plot, the spray frequency was reduced to eight rounds, out of which only two rounds of fungicides were used for disease management. This resulted in an 85% reduction in pesticides in comparison with the farmer practice plot. Insect pest management in the IPM plot was carried out using food spray, neem extract and commercially produced Nimbecidine – made from neem.
On average, the spray frequency for both the IPM plots from the two villages was 8 rounds, with only 1.5 rounds of pesticides applied. In the farmer practice plots, an average of 14.5 rounds of pesticides were applied. Hence, in comparison with the farmer practice plots, the average pesticide use and spray frequency in the IPM plots was reduced by 90% and 45%, respectively. A substantial difference.
Even though pesticide use was significantly reduced, onion yields substantially increased. In Quhar Michael, the onion yield from the IPM plot was 49% higher than the yield obtained from the farmer practice plot. In Quhar Abo Village, the onion yield from the IPM plot was 56% higher.
Furthermore, the total production cost in the Quhar Michael IPM plot was 12% lower than in the farmer practice plot, mainly due to reduced plant protection input costs. In Quhar Abo, the production cost in the IPM plot was 38% higher than the farmer practice plot due to an increase in the labour cost. However, the plant protection input cost was reduced.
Overall, the higher onion yields coupled with lower pesticide input costs resulted in increased profits for the IPM plot versus the farmer practice plot, with a 187% higher net income in Quhar Michael and an 83% higher net income in Quhar Abo.
This case study thus further demonstrates that by adopting IPM systems for onion, smallholder farmers can increase their yield and reduce their production costs, which then maximizes their net profit. As well as the economic benefits, the reduced use of toxic pesticides reduces the adverse impacts on human health, bees and other beneficial insects.
Figure 20. IPM farmer learning day at Quhar Michael, Amhara, Ethiopia.
references
1. Kebede, H. and Ermias Birru, E. (2011). Guideline on irrigation agronomy, Ministry of Agriculture, Ethiopia and GIZ.
2. Habtewold M., Dane C., and Ayza A. (2021). Participatory Evaluation and Demonstration of Onion Spacing in Irrigated Agriculture at Kencho Kebele in Uba Debre Tsehay Woreda, Southern Ethiopia, Ethiop. J. Agric. Sci. 31(2) 105-114.
3. Olani N. and Fikre M. (2010). Onion Seed Production Techniques. A Manual for Extension Agents and Seed Producers.
4. Selamawit Ketema, Lemma Dessalegn, Buzuayehu Tesfaye. (2013). Effect of Planting Methods on Maturity and Yield of Onion (Allium cepa) in the Central Rift Valley of Ethiopia. Ethiop. J. Agric. Sci. 24:45–55.
5. Ministry of Agriculture (2018). Plant variety release, protection and seed quality control directorate; Issue No.21, Addis Ababa.
6. FAO and WHO (2014). International Code of Conduct on Pest Management, Rome.
7. Geck, M. S., Crossland, M., and Lamanna, C. (2023). Measuring agroecology and its performance: An overview and critical discussion of existing tools and approaches. Outlook on Agriculture, 52(3), 349-359.
8. http://www.fao.org/agroecology
9. Watts, M. and Williamson, S. (2015). Replacing Chemicals with Biology: Phasing out Highly Hazardous Pesticides with agroecology. PAN International
10. PAN UK, IDH and PAN Ethiopia (2024). Supporting healthy, sustainable and productive smallholder vegetable farming, Project report, unpublished.
11. PAN UK and PAN Ethiopia (2024). The Integrated Pest Management Ladder: A framework and toolkit for onion farmers and trainers, Pesticide Action Network UK and Pesticide Action Nexus Association Ethiopia.
12. Megersa H.G. (2017). Onion (Allium cepa L.) Yield Improvement Progress in Ethiopia: A Review, Inter J Agri Biosci, 6(5): 265271.
13. Rehman, S.U., De Castro, F., Aprile, A., Benedetti, M. and Fanizzi, F.P. Vermicompost: Enhancing Plant Growth and Combating Abiotic and Biotic Stress. Agronomy 2023, 13, 1134. https://doi.org/10.3390/ agronomy13041134.
14. https://www.pan-uk.org/?s=food+spray+manual
15. Collier, R. (2023). Pest insect management in vegetable crops grown outdoors in northern Europe – approaches at the bottom of the IPM pyramid. Frontiers in Horticulture 2.
16. Alston, D.G. and Drost, D. (2008). Onion Thrips (Thrips tabaci). Utah State University Extension Publication ENT-117-08PR.
17. Taye Asfaw (2015). Thrips monitoring and threshold Ethiopian Ministry of Agriculture and Ziway Plant Health Clinic, CABI Plantwise.
18. Latin, R. and Helms, K. (2001). Diagnosis and Control of Onion Diseases, Purdue University, Cooperative Extension Service, Indiana
19. MoA, Oromia Bureau of Agriculture, Bureau of Agriculture of Amhara Region and JICA (2019). Bulb onion production: Smallholder Horticulture Farmer Empowerment through Promotion of Market-Oriented Agriculture, Addis Ababa.
20. Shanmugasundaram, S. and Kalb, T. (2007). AVRDC training guide: suggested cultural practices for onion. The World Vegetable Centre.
Integrated Pest ManageMent for onIon cultIvatIon
a manual for smallholder farmers in sub-saharan africa with special focus on ethiopia
March 2025
Pesticide Action Network UK
PAN UK is based in Brighton. We are the only UK charity focused solely on addressing the harm caused by chemical pesticides. We work tirelessly to apply pressure to governments, regulators, policy makers, industry and retailers to reduce the impact of harmful pesticides. Find out more about our work at: www.pan-uk.org
Registered charity 327215
Pesticide Action Nexus Association Ethiopia
Pesticide Action Nexus Association Ethiopia (PAN-Ethiopia) is a civil society organization that works towards a safe and sustainable environment protected from harms posed by pesticides and other hazardous chemicals through the close collaboration of government, non-governmental organizations, civil society interest groups, and urban and rural communities. It is actively involved in many global policy negotiations and has a Special Consultative Status with Economic and Social Council (ECOSOC) of the United Nations since July 2012. Email: pan.ethiopia@gmail.com
Bees for Development Ethiopia
Based in Bahir Dar, Amhara BfDE works to develop beekeeping towards supporting sustainable and resilient livelihoods in Ethiopia, in harmony with the environment. Work focusses on training, education, advocacy, habitat conservation and strengthening market links. Learn more at: https://beesfordevelopmentethiopia.org
Bees for Development UK
Based in Monmouth, South Wales, Bees for Development works to harness the power of bees towards achieving the Sustainable Development Goals. We train beekeepers and help them to market their produce. We strengthen farmers’ livelihoods, through the integration of beekeeping on farms to support optimal pollination and additional revenue streams. Find out more about our work at: www.beesfordevelopment.org
