When a Pesticide Doesn’t Work

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Now that we are in the middle of the growing season, some of you reading this have probably already lost a battle with some type of pest. A prized possession in your lawn or garden may have succumbed to a pesky disease, insect, or weed. Don’t feel alone – this is a challenge even for the professionals!

North Carolina Cooperative Extension recommends an integrated approach to managing pests. This simply means using all the available tools in the tool box like planting date, variety selection, mechanical cultivation, improved drainage, use of natural enemies, and/or mulches. These are examples of biological, cultural, and mechanical controls that should be part of a management plan. When combined with these other methods, chemical control can also be used to effectively manage pests, even in organic production. Although many people assume organic means pesticide free, there are products approved for use in organic systems.

Pesticides are just one tool that can be used to help win the battle with pests, but sometimes their control might not be as good as planned. I would like to offer some common situations that might explain why a pesticide application failed.

  1. Improper Identification – The first and most important thing to do is properly identify the target pest(s). Being able to accurately identify pests requires practice and patience as subtle differences can sometimes lead to false identification. Seek expert advice – there are many resources available to assist you. Reference materials such as Extension bulletins, field guides, and websites can be very useful in identifying pests.
  2. Improper Product Selection – Once you have properly identified the targeted pest(s), you can begin selecting an appropriate product for the situation. This can seem like an overwhelming process with the numerous products available. Try to select products that will allow natural enemies to remain in the production system to avoid a pest resurgence. Identify the life cycle of insects, growth stage of weeds, or signs of a disease to help choose the best product. Make sure the label specifies the desired use site and pests.
  3. Incorrect Timing of Application – I’ve heard it said many times, “timing is everything,” and that is often the case with pesticides. Know what the correct application time is for the selected product. Preemergent herbicides need to be applied before the weed seeds actually germinate. If you have weeds already present, consider using a post-emergent product. Some preemergent herbicide and insecticide products may need to be applied before a scheduled irrigation or rain event for activation. Typically, pests are easier to control when they are small or early in their life cycle, so check the label for size restrictions.
  4. Unfavorable Environmental Conditions – Extreme weather conditions can play a huge factor in the performance of a pesticide. High temperatures like we have been experiencing lately can reduce uptake of the chemical as plants conserve water. Make applications when plants are actively growing and not stressed. Allow enough dry time between application and forecasted rain.

Contact your local Extension Center to help make your next pest battle a success. For more information, please contact Mac Malloy, Extension Field Crops Agent with North Carolina Cooperative Extension, Robeson County Center, at 671-3276, by E-mail at Mac_Malloy@ncsu.edu, or visit our website at http://robeson.ces.ncsu.edu/.

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