October 2, 2003

The Australian Cotton CRC has developed the world’s first detailed guide to the impact of individual insecticides on beneficial insects that act as natural predators of cotton pests.

Prepared in a simple to use calendar form, the guide is available in either printed or electronic versions, and is accessible on the CRC website and in CD decision support systems distributed by the CRC.

To download the two-page PDF file go direct to:
Impact of insecticides and miticides on predators in Cotton (October 2002)

Dr Lewis Wilson from CSIRO Plant Industry, a program leader with the CRC, said the guide represented further progress in the cotton industry’s ongoing strategy to reduce insecticide use, and position insecticide sprays as a “last resort” policy.

“Research has shown that by focussing on conserving the natural enemies of major cotton pests such as helicoverpa, mites, aphids, mirids and tipworms, it’s possible to significantly reduce insecticide use, without impairing yield, fibre quality, crop maturity or profitability.

“Until now we have not had available to cotton growers an easily accessible ready-reckoner ranking the impact of individual insecticides and proprietary products on these beneficial insects,” Dr Wilson said.

The new guide is in the form of a colour-coded calendar that identifies which major target pests of cotton each insecticide will control, and concurrently lists the effect of the insecticide against natural enemies, so called beneficial insects.

At a glance, cotton growers, agronomists, consultants and resellers can easily and quickly identify insecticides recommended against major pests, and compare the impact of those same insecticides on beneficials such as beetles, bugs, spiders, wasps and ants.

“They can use this information to select the insecticide with the least impact on the natural enemies. This helps their survival so they can continue to contribute to control of pests, thereby reducing the need to spray and the risk that other pests will also become problems,” he said.

All insecticides are rated for their impact on beneficials as either very low (less than 10 per cent impact), low (10-20 per cent) moderate (20-40 per cent), high (40-60 per cent) or a very high (above 60 per cent) impact.

The guide has also proven to be a useful tool for Australian Cotton CRC economists as a way of comparing the costs and benefits of different insecticide regimes applied to cotton fields.

A case study of 12 farms near Boggabilla in northern NSW over five seasons has demonstrated that fields managed with 'soft' low impact insecticides can be just as profitable as cotton fields managed using a 'harder' spectrum of insecticides over the growing season.

Insecticides have also been identified on the calendar that are likely to increase the risk of pest outbreaks or resurgence if repeatedly applied.

This resurgence often results when insecticides targeted against one pest, say Helicoverpa, kill off predators of another pest that is not affected by the insecticide, say mites. In this case the mites can increase unchecked, becoming what is known as a secondary pest outbreak.

Dr Wilson said the beneficial insecticide index calendar incorporates and integrates years of research by CSIRO, NSW Agriculture, the Queensland Department of Primary Industries and the Cotton CRC.

“This new guide forms a key part of our Integrated Pest Management Guidelines for cotton. If the new guide is followed, over-use of insecticides, insecticide resistance, disruption to the natural enemies of major pests, high production costs, and major environmental damage, can be reduced and avoided,” Dr Wilson said.