REARING GREYBACK BEETLES

- TO EXPLORE ALTERNATIVE CANE GRUB CONTROL

Apopular activity at SRA’s recent Meringa Field Day was a tour of the entomology facilities to see ongoing research close-up.

Entomology Leader Dr Kevin Powell and Entomology Research Technician Dr Samuel Bawa treated visitors to the joys and challenges of tackling Greyback canegrub control.

Background

• Canegrubs attack sugarcane worldwide

• In Australia there are 19 native species of canegrub

• Canegrubs are the most economically important insect pest - costing the sugar industry an estimated $32 million to $59 million a year

• Greyback is the most common species and is found in several canegrowing districts.

Current control

• Since 2001 imidacloprid, a systemic insecticide belonging to a class of chemicals called neonicotinoids, has been highly effective

• Neonicotinoids are the only actives registered for use against canegrubs in Australia

• Neonicotinoids are under review by the Australian Pesticides and Veterinary Medicines Authority (APVMA)

• Future control alternative pesticide control options are being explored by SRA in collaboration with three agrochemical companies.

Stage 1

Methods

Screening of alternative pesticides (both chemical and biorational) to imidacloprid is done as follows:

YEAR 1-2

Laboratory pre-screening is done targeting Greyback canegrub larvae using three methods:

• Potted plants – to examine any systemic activity via the root system

• Carrot diet – to look at pesticide ingestion and contact effects

• Artificial diet (based on sugarcane root chemistry) - to look at pesticide ingestion and contact effects. The laboratory screening determines (i) which pesticides to select for field trials and (ii) the optimal rate of application required.

YEAR 3-4

Field trials to determine:

• Efficacy of alternatives in the field and optimal field application rate and timing – compared to imidacloprid

• Product persistence in the soil on fig leaves

• Run-off properties.

Stage 2

Stage 3

The eggs are incubated in hatching chambers under ideal conditions until they hatch into larvae. The larvae are then separated and incubated.

STAGE

5

When grubs get to the right life-stage (called second instar) they are used in pesticide screening bioassays which can be on either carrot, artificial diet or in potted plants.

Stage 7

Sometimes treatment affects the grub size and weight so this is also assessed. These grubs are the same age. The grub on the left was treated with pesticide and is smaller than the grub on the right (which was only treated with water).

Stage 4

Once the larvae are large enough they are placed in feeding chambers and reared on carrots. Because grubs are cannibalistic they have to be reared in individual chambers, otherwise they will eat each other!

STAGE 6

Each treatment is carefully labelled and weekly measurements are made to see if the grubs are killed by the treatment.

Next Stage

Once all the treatments have been tested rigorously in the laboratory those that are reducing grub survival and development will be selected for field trial assessment.

RESULTS & CONCLUSIONS

• Pot and carrot trials are ongoing but some products are already showing promise with similar efficacy to imidacloprid.

• Some products reduce survival, food intake, activity and grub development.

• Once all laboratory trials have been completed and fully analysed, field trials will be established.

• The project will provide data to support potential registration of alternative products.