Resistance
An Integrated Approach to IRM
The most effective strategy to combat insecticide resistance is to do everything possible to prevent it occurring in the first place. To this end, crop specialists recommend IRM programs as one part of a larger IPM approach covering three basic components: monitoring pest complexes in the field for changes in population density, focusing on economic injury levels and integrating multiple control strategies.
Monitoring Pests
Scouting is one of the key activities that users of insecticidal products can implement as part of their insecticide resistance management strategy. Farmers should follow the progress of insect population development in their fields (with or without the assistance of a crop consultant or advisor), to determine if and when control measures are warranted. They should monitor and consider natural enemies when making control decisions. After treatment, they should continue monitoring to assess pest populations and the effectiveness of any control measures implemented. Many similar considerations apply to the control of public health pests.
Economic Thresholds
Insecticides should be used only if insects are numerous enough to cause economic losses that exceed the cost of the insecticide plus application, or where there is a threat to public health. Exceptions are in-furrow, at-planting or seed treatments for early season pests that from experience it is known usually reach damaging levels annually. Farmers are always encouraged to consult their local advisors about economic thresholds of target pests in their areas.
Integrated Control Strategies (1)
Incorporate as many different control strategies as possible including the use of synthetic insecticides, biological insecticides, beneficial insects (predators/parasites), cultural practices, transgenic plants (where allowed), crop rotation, pest-resistant crop varieties and chemical attractants or deterrents.
Applications of insecticide must be timed correctly, targeting the most vulnerable life stage of the insect pest. The use of spray rates and application intervals recommended by the manufacturer and in compliance with local agricultural extension regulations is essential.
It is important to mix and apply insecticides carefully. As resistance increases, the margin for error in terms of insecticide dose, timing, coverage, etc., assumes even greater importance. Recommendations from manufacturers and local advisors should be followed.
A key element of effective resistance management is the use of alternations, rotations, or sequences of different insecticide MoA classes. Users should avoid selecting for resistance or cross-resistance by repeated use within the crop cycle, or year after year, of the same insecticide or related products in the same MoA class.
Integrated Control Strategies (2)
It is important to consider the impact of pesticides on beneficial insects, and use products at labeled rates and spray intervals to minimize undesired effects on parasitoids and predators.
Preserve susceptible genes. Some programs try to preserve susceptible individuals within the target population by providing a refuge or haven for susceptible insects, such as unsprayed areas within treated fields, adjacent refuge fields, or attractive habitats within a treated field that facilitate immigration. These susceptible individuals may out-compete and interbreed with resistant individuals, diluting the impact of any resistance that may have developed in the population.
Consider crop residue options. Destroying crop residues can deprive insects of food and overwintering sites. This cultural practice will kill pesticide-resistant pests (as well as susceptible ones) and prevent them from producing resistant offspring for the next season. However, farmers should review their soil conservation requirements before removing residues.
