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Health Home&&wellbeing Garden special

Good bugs, bad bugs How to manage your garden pests naturally

As an organic consumer you do your best to avoid chemicals in your home but are you as mindful of chemical use in the garden? As Eve Valensise discovers, you don’t have to resort to chemical warfare in order to control destructive insects – you just need to introduce some beneficial ones. A healthy garden ecosystem should be home to a variety of insects. Generally a problem arises when an imbalance in this ecosystem occurs, allowing one species to dominate. Biodiversity is important for garden health because it allows a variety of habitats and food for

a broad selection of insects rather than a limiting monoculture environment. If an imbalance in your garden occurs and you find yourself with an overpopulation of an undesirable bug you can rest assured there are alternatives to dangerous chemicals that can ensure your organic

way of life is continued into your garden. These alternatives fall under the umbrella of Integrated Pest Management (IPM), an approach that encourages the reduction of pesticide use through maximising biological controls.

Integrated Pest Management

The key to IPM is the ability to be observant as you understand the relationships between beneficial insects and those you want to discourage. The first step to implementing an IPM program should involve biological controls. This involves the use of other organisms to keep pests under control. There are four different types of biological control – two are mainly applicable to

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large-scale situations and the other two can be successfully implemented as part of an IPM program in your own garden. Biological controls for large-scale situations Classical biological control This involves the introduction of the exotic pest’s natural enemy from its home of origin into the imbalanced environment. One of the most successful cases was the 1996 introduction of Trichopoda giacomellii, a type of parasitic fly, to reduce green vegetable bug populations that were feeding on northern NSW pecan crops, leading to spoilage of the nuts. After the release, the fly populations were reduced by up to 80 per cent. Control by using pathogens This method of control is commercially available and is sprayed onto the affected area. The spray contains bacteria, viruses or fungi that cause disease in the bad bugs. To be successful, this type of control needs to be applied to coincide with the lifecycle of the pest. Biological controls suitable for the home garden Control by naturally occurring beneficial organisms This involves encouraging the good bugs that naturally occur in your garden in order to maintain a balanced environment. The use of broad-spectrum pesticides kills these beneficial organisms

“To encourage beneficial insects into your garden you can create your own garden insectary by adding plants that attract predatory bugs.” as well as the bad and can lead to an outbreak of unwanted pests without the beneficial bugs to keep them in check. Control by releasing mass-reared beneficial organisms Generally batches of mass-reared good bugs from off site are bought and released into the affected area. This method of control can be useful in situations where the natural populations of predatory insects have been diminished because of unfavourable weather or pesticide use.

Encouraging beneficial insects to your garden

To encourage beneficial insects into your garden you can create your own garden insectary by adding plants that attract predatory bugs. A garden insectary works on many levels, including providing habitat for the good bugs – providing an alternative source of food for the bad while also providing a source of food for the insects you want. This is not a short-term solution for pests in the garden, however over time, when the garden establishes and the populations of good bugs grow, you will be able to eliminate the need for harsh pesticides and chemicals. For larger gardens that have more space to work with, dedicate a garden bed to your insectary, or interplant throughout

your garden. If space is at a premium, a pot or trough would be adequate. Diversity is the key to success in your insectary. A combination of around seven different species can be enough to lure predatory insects into your garden. Some successful plants include coriander, caraway, dill, fennel, parsley, calendula, thyme, rosemary, mint, chamomile, lemon balm, alyssum, convolvulus, cosmos, dahlia, shasta daisy and sunflower.

When the good bugs won’t come When cultivating healthy populations of beneficial insects, there are several places where you can purchase some to boost population numbers. These insects will prey on the resident pests or their young. Below are the names of some beneficial insects that might help to rebalance the ecology of your garden.


Prey: mealybug, pulvinaria scale, cottony cushion scale and other soft scales These native Australian beetles and their larvae feed on mealybug eggs, young nymphs and the mature mealybug. The mature female Cryptolaemus will lay her eggs amongst the mealybug eggs, providing her young with a food source after they hatch. Depending on the diet of

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the adult female, she can lay up to 500 eggs in her lifetime. The lifecycle of the Cryptolaemus is about four to seven weeks, which is roughly the amount of time it will take to see significant results. If the mealybug infestation is prolific, top-up releases will need to be conducted and therefore results may be seen after two or more generations.

Simple ways to control insect pests If some of the following insects are a problem, try these simple, environmentally safe solutions to move them on.


The simplest solution for deterring ants is to keep the area clean and dry. If you have found their entry point you can block it with things they detest such as dry mint, cayenne pepper, citrus oil, cinnamon, lemon juice or coffee grounds.

Aphids and mealybugs

Green lacewing

Prey: aphid, twospotted mite, greenhouse whitefly, mealybug, scales, moth eggs and small caterpillars This native Australian insect is quite useful as it feeds on a broad range of garden pests. Better suited to warmer climates, lacewing is best utilised on shrubs and trees. The adult female can lay up to 600 eggs. Once these hatch, the larvae feast voraciously and can eat up to 60 aphids in one hour! The adult lacewing however will not consume pests – instead they feed on pollen and nectar so it is important that flowering plants are close by. Lacewings live up to four weeks, so checking your garden for pests around 30 days after release is suggested. Depending on your situation, lacewings should be released at specific intervals. Entomopathogenic nematode (Heterorhabditis zealandica) Prey: African black beetle, Argentine stem weevil, blackheaded cockchafer, Argentine scarab and bill bug weevil This microscopic organism attacks when its prey is still larvae. The nematode is attracted to the larvae and enters it through its orifices. Once inside the host, the nematode releases symbiotic bacteria, which provide it with food. Two weeks after it has entered the host it has reproduced so rapidly that the larvae dies and bursts to release about 100,000 times the number of nematodes that originally infected it. This type of nematode is most commonly used to deal with African black beetle, which destroys turf and has been a problem throughout Australia for over 100 years. Depending on your situation, nematodes should be released at specific intervals. O More info: Llewellyn R (Ed.), 2002, The Good Bug Book, Integrated Pest Management Pty Ltd for Australian Biological Control Inc.: the Association of Beneficial Anthropod Producers, Richmond, NSW

Mix together 1 tablespoon of canola oil, 3 drops of pure soap and 1 litre of water and pour into a spray bottle; ensure that you spray tops and undersides of leaves.


Yates sells a spray-on product called Dipel, which selectively targets caterpillars. It contains Bacillus thuringiensis, which is a naturally occurring bacteria that poisons the caterpillar’s stomach after ingestion. This bacteria does not harm other insects, birds, fish or warmblooded animals.

Lawn grub

Release entomopathogenic nematode (see above)

Slug and Snail

Slugs and snails are active in the cool, damp evenings. Thus, watering your garden in the evening only makes conditions more desirable for them. Try watering in the mornings before taking any further action. If you want to create a trap that kills them, lure them in with beer! Bury a jar in the soil and fill with a small amount of beer – the snails and slugs will crawl into the jar and drown.


Simply boil the kettle and pour directly onto weeds – this will kill the weed, which you can then remove by hand.

Whitefly, fruit fly

Try ‘yellow sticky traps’ – a sheet form of sticky paper that can be cut to size and hung or laid in the garden. The glue that covers their surface doesn’t dry out or become ruined in the weather. This is a useful way to monitor the pests that are in your garden.

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