An effective strategy to minimize the selection for resistance to a particular insecticide group is to rotate products from groups with different modes-of-action.
- Avoid using the same mode-of-action against successive pest generations.
- Using the same class of insecticide multiple times against one generation is acceptable.
- Choose a different class of insecticide to target the next generation to avoid developing resistant populations.
- Use the group number developed by the Insecticide Resistance Action Committee (IRAC) to identify the class of insecticide to which each product belongs.
Avoiding overuse is another important principle in managing insecticide resistance. Employing pheromone mating disruption as part of an Integrated Pest Management (IPM) program will help to reduce insecticide inputs.
The mode-of-action of an insecticide refers to how it kills the insect. While many new insecticides have been registered over the past few years, many share the same mode-of-action. To help growers determine the mode-of-action group that a product belongs to, IRAC (Insecticide Resistance Action Committee) has developed a classification scheme. These scheme classifies insecticides into groups marked with a group number (like 13A) depending on their mode-of-action and active ingredient. The group number appears on the label of most of the new products and is listed in DAS in the full WSU Spray Guide under “resistance class.” The group number can help to determine which products could be used in a rotation strategy to create a sound resistance management program. Particular caution is advised if you use pre-mixed insecticides that contain different active ingredients with different modes-of-action.
A simple checklist can help to track the insecticide products that you are using. In the sample below, the growing season is divided into two parts – based on the development cycles for codling moth and leafrollers. If a product is used in the first part of the season, it is marked with an “X.” It is possible to use a product with the same group number, or even the same product, more than one time in the first part of the season because only one generation of a pest is exposed to that mode-of-action. However, the early-season choices limit what products can be used in the second part of the season if a sound resistance management program is being followed. If an insecticide is used in the first part of the season, all insecticides in the group are crossed off the table as options for use in the second half of the season.(PMTP Team, WSU-TFREC)