Manage Resistance Now


Concern about insecticide resistance in Canada is increasing among growers. Resistant insects rob a crop of yield. Losses may be unnoticed at first, but pest reproduction is exponential and can quickly result in significant yield reduction. Practices that prevent or delay the development of resistance will protect your profitability and ensure the crop protection products we have today will continue to be effective well into the future.




Resistance best management practices (BMPs) include a combination of physical, cultural, biological and chemical control measures. Start today to manage fungicide resistance on your farm.

Before using an insecticide, you should always identify the pest correctly and monitor population levels in the crop. Only treat if action thresholds (i.e., pest numbers or damage level) are met or if forecasting models expect them to be met.

  • Identify the insect pest and its life cycle stage
    • Misidentifying the insect may lead to incorrect insecticide use, which contributes to resistance development. Take a sample to your crop advisor if needed.
    • For insecticides to be most effective, you must also be aware of the life cycle and life stage of the insect. Some insect life stages take place in the soil where they are protected from insecticide sprays. Knowing where the pest is at in its life cycle will help predict when the pest is most vulnerable to insecticide applications.
  • Monitor pest presence regularly, including after treatment
    • Monitor for pests in or around the crop, including field and orchard edges, and near any damage to the crop that could have been caused by the pest.
    • Monitoring methods differ between insects: some must be counted on leaves, some are caught using sweep nets, and some are caught on traps. Action thresholds are given in the same unit as the monitoring method (e.g. # adults/sweep) so make sure you know how to monitor for the insect in question.
  • Follow action thresholds
    • When regular scouting indicates pests are below the action threshold or not at the stage when application would be most effective, insecticide use can be avoided or delayed.
    • Be aware of recommended action thresholds or forecasting models to predict the best timing for insecticide application.
    • Spray when an insect pest reaches its specific action threshold (the number of pests or level of pest damage at which treatment is effective). Consult with your crop advisor or provincial Ministry of Agriculture for action thresholds on specific pests.

Click here for more about Evaluating the Need for an Insecticide

Test your knowledge

When choosing chemical insecticides, select the right products for the right insect pest on the right crop. Follow practices such as rotating chemical groups and applying products according to label directions and economic thresholds.

  • Rotate among chemical families
    • Chemicals are classified by mode of action (MoA) and are categorized by groups based on the action of an insecticide at its target site. Insecticide labels include numbers and letters on the front panel to indicate which Group they belong to.
    • Multiple applications (generally less than three) of the same MoA insecticide are acceptable if they are used to treat a single insect generation or are used within a window.
    • A window is the duration of an insect generation or approximately 30 days.
    • Following a window of any MoA group, rotate to an insecticide from a different MoA group in the next application window.
    • Insecticides that include multiple MoA groups are effective and recommended, but be sure to rotate to different MoA groups in the next application window.
    • If a pest generation is difficult to discern, then use approximately 30 days as the length of a treatment window for rotation.
    • For short cycle crops (<50 days), the duration of the crop cycle should be considered as a window, so it is recommended to alternate to a different MoA for the next crop cycle.
    • For pests with only a single generation per year, consider rotating products from different Groups in alternate years.
    • Don’t re-spray an area with a product of the same group in the same season where insect resistance has been verified.
  • Maximize spray impact
    • Always read the insecticide label and follow both the recommended rates and water volumes for good crop coverage.
    • Ensure that spray rigs and nozzles are properly chosen and calibrated to achieve good coverage, especially for contact insecticides and crops with thick canopies.
    • Scout and consider farm history when selecting seed treatments for your operation.
    • Keep in mind that a product could fail for reasons other than insecticide resistance.
    • Insecticide mixtures (‘tank mixes’) are not primarily used for purposes of IRM but may offer benefits when included in a rotation strategy with other modes of action. Mixtures have the advantage of targeting multiple pests at once, increasing the level of control of a single target pest, and providing more complete control of a pest generation by impacting other life stages (e.g., adult, egg). If your pest situation requires the use of a mixture, ask a crop advisor for options that will minimize resistance risk.

Click here for more about Following Insecticide Best Practices

Test your knowledge

Integrated Pest Management (IPM) includes a combination of cultural, biological and mechanical controls.

  • Cultural – Use practices that make the environment less attractive to insect pests:
    • Choose pest-resistant crop varieties.
    • Vary planting dates to avoid peak activity times of the pest. For example, planting early allows plants to become well established and therefore more tolerant to pest attack.
    • Rotate your crops. Plant a host crop as far as possible from where it was grown previously or from where a neighbouring field will have a similar crop.
    • Keep crops healthy and be aware of sources of stress such as nutrient deficiency, pests and weather conditions.
  • Biological – Conserve natural enemies to help reduce pest pressure:
    • Maintain a habitat for natural enemies, also called beneficial insects, that includes flowering plants, shrubs, clean water and nesting sites.
    • Be mindful of beneficial insects if you do need to apply chemical control for insect pests.
    • Choose the right insecticide for the right pest on the right crop. Apply only when damage and thresholds are met or are expected to be exceeded.
    • Consult the label for information about times to avoid spraying (e.g., when pollinators are foraging).
    • Minimize spray drift to reduce harmful effects on beneficial insects in existing habitats next to the application site.
  • Mechanical – Manage pests using physical barriers:
    • Use plastic mulch on raised beds to reduce damage from soil-based insect pests; row covers to minimize flying pests; and screening on greenhouses vents.
    • In horticultural operations, physically remove and destroy infested plants and, when possible, the pest itself.
    • In field crops, remove weeds that host pests such as winter annuals for cutworms or buckthorn for soybean aphids.
  • Biopesticides – Consider products created from bacteria, fungi, plants and minerals:
    • Biopesticides can fit very well into IPM systems, as many work best at lower pest pressures and can be used in combination with scouting and monitoring.
    • Pheromones (chemicals that insects use to communicate within their own species) are used for mating disruption or ‘attract and kill’ strategies.
    • Microbial pesticides, which contain living organisms such as algae, viruses, fungi and bacteria, can be used for species-specific pest control.

Click here for more about Practicing Integrated Pest Management.

Test your knowledge
  • Keep good spray records, so that you know in future years which insects were present in which fields, which insecticides were used and where, and how much control was achieved.
  • Consider using refuge and/or trap crops, which is a crop planted to attract pests and lure them away from the main crop. Trap crops can be spot-treated instead of applying full field treatments. They can also be used as part of a pest monitoring program.
  • If you suspect that you have insect resistance, contact a crop advisor, company representative or your local extension expert.

Case Studies

Canadian growers, advisors and experts talk about their experiences managing insecticide resistance.


Insecticide Resistance Management

CropLife International and IRAC explains the importance of mode of action in insect resistance management.