CSIRO is developing ways to better control and manage emerging cotton pests to reduce their potential impact on the cotton industry.
Insect resistant GM cotton, which controls caterpillars of Helicoverpa, the main pest of cotton, has reduced insecticide use by 80 per cent. Ironically, reduced insecticide use against Helicoverpa has allowed other pests to survive and emerge as important pests. CSIRO Plant Industry is looking at these emerging pests, including aphids, mirids, thrips and jassids to improve our management strategies.
Aphids
Aphids are now occurring earlier in the season. With our collaborators we are identifying the amount of damage they cause and ways to reduce yield loss and insecticide use by researching:
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better sampling techniques and better aphid thresholds
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plant hosts that aphids use, other than cotton, and ways to manage them
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key aphid predators and parasites
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insecticide resistance in aphids (with Qld DPI&F)
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some new fungal bio-pesticides (with NSW DPI)
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if aphids on cotton all come from one particular host plant or many (with NSW DPI and French National Research Institute for Agricultural Research).
Results will be included in the CottonLOGIC computer program to help growers manage aphids.
We are also studying the disease Cotton Bunchy Top (CBT), a disease transmitted by aphids, to:
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develop a tool to predict its spread
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identify alternative hosts of the disease and how to manage them
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breed CBT resistant cotton varieties.
Mirids
Mirids are also occurring later in the season now. We know fibre quality is not affected by mirids but we want to determine the effect of mirids on older plants, particularly how they compensate for boll damage to determine potential yield loss.
We have been evaluating different mirid sampling techniques to identify accurate mirid numbers to help growers decide which technique to use and when to control mirids.
Our mirid research data also ends up in CottonLOGIC to update mirid thresholds and to help growers determine mirid control.
Other emerging pests
Thrips feed on cotton leaves and damage the upper leaves. Recently thrips have become more abundant late in the cotton season. We are investigating the effect of late damage to plants on yield and fibre quality. Thrips also eat the eggs of spider mites, which can cause significant yield loss, so balancing potential thrips damage against their benefit is important.
Jassids feed on the upper surface of leaves causing white dots that can reduce photosynthesis. Recently jassid numbers have been higher, especially late in the cotton season. By using real and simulated jassid damage we are determining any yield loss and when control might be required.
Other pests being observed to gauge their status include:
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green vegetable bug
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cotton stainer
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cotton harlequin bug.
Non-target effects of insecticides
Insesticides may reduce numbers of beneficial insects that help control pests, or encourage secondary pests not controlled by the insecticide.
Our research is evaluating these non-target effects. The results are published yearly in a guide for cotton growers to help them manage insecticide use.
Non-target effects of GM cotton
There are no significant effects of GM cotton on non-target species, including beneficials or those involved in breaking down plant residues after harvest.
However, some cotton growers have noted more spider mites in GM crops. We suspect this is probably due to the different insecticides used in GM crops. We are investigating if such differences are real and if so if they are due to different insecticide use patterns or to other factors. The research is continuing in collaboration with CSIRO Entomology.
Integrated Pest Management
Integrated pest management (IPM) manages pests using a wide range of methods:
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plant resistance to the pests
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destruction of over-winter food sources
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management of over winter forms
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use of trap crops
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tolerance of non-economic damage
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effective sampling and pest control thresholds
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insecticides (as a last resort).
Our IPM research is available to help growers in the ‘Integrated pest management guidelines for cotton production in Australia’.
Related information sheets
Related scientific papers
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