Insecticide resistance is a reduction in the susceptibility of a pest population to a particular insecticide or insecticide group. The change is heritable, and natural selection can result in a rapid increase in the proportion of the population with resistance, leading in inadequate control of the pest at the insecticide's registered rate. An incursion of resistant exotic strains of our endemic pests could also introduce resistance to into local populations.
It is important to scientifically confirm suspected cases of insecticide resistance as field 'spray failures' can be due to inadequate coverage or other application issues, including water quality or incompatible product mixes.
To help maintain the sustainability of broadacre production systems, Research and Development Corporations (CRDC and GRDC) support insecticide resistance surveillance programs of major pest species, including helicoverpa, aphids, mites, mirids and whiteflies.
Focused on detecting resistance to key insecticides used against these pests, these programs provide growers and advisors with an early warning system for potential resistance outbreaks, help maximise the effectiveness of spray applications, and are essential for informing ongoing review and improvement of industry-endorsed resistance management strategies.
This predictive capability means industries can implement management tactics for reducing economic losses well before spray failures occur, as well as minimising further spread of resistance genes throughout the wider pest population.
NSW DPI conducts ongoing helicoverpa insecticide resistance surveillance program in the major summer cropping regions of NSW and Queensland using F2 screening which is highly sensitive for all types of known and novel resistance even when resistance genes are recessive. NSW DPI also conducts resistance testing for aphids, mites and mirids.
Queensland Department of Agriculture and Fisheries staff make collections of silverleaf whitefly during the latter half of the cotton season on farms in Queensland and NSW, establishing and maintaining colonies for resistance testing of commonly used products.
Insecticide resistance surveillance results
Resistance management strategies
Minimise the risk of insecticide resistance development through the following strategies:
- Use economic thresholds to minimise insecticide use - do not apply 'insurance' sprays
- Avoid broad-spectrum insecticide use (particularly early in the season) where possible as these products reduce beneficial populations which can lead to flaring of other pests and place further selection pressure on pest populations
- Adhere to industry recommended application windows to limit exposure to any one MoA group
- Avoid the consecutive use of any one MoA group (including following a seed treatment with the same MoA foliar) - rotate between groups where possible and do no exceeed the maximum number of sprays stated on the lable
- Do not respray an apparent failure with a product from the same MoA group.
The cotton industry's Insecticide Resistance Management Strategy (IRMS) is updated annually and published in the Cotton Pest Management Guide. A hard copy is posted out with the spring edition of Spotlight. Download IRMS 2023/24 here.
Users of Bollgard technology must adhere to Bayer's Resistance Management Plan (RMP) for their region.
The Beatsheet contains detailed information on resistance mechanisms and surveillance programs.
Examples of other resistance management strategies for pests in the grains industries (including an explanation of the science behind them) are available at IPM Guidelines for Grains.
Information on insecticide mode of action groups is available from the Insecticide Resistance Action Committee (IRAC).