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In-Season

IPM Know-How & Presticide Resistance

Insects can take a bite out of producers’ yields.

Dr. Janet Knodel, Extension Entomologist and Professor at North Dakota State University, recommends that before taking action against pests with insecticides, producers should use Integrated Pest Management (IPM) strategies.

“That means getting out and scouting fields weekly throughout the season,” she says. “As key pests come into critical windows, when they’re increasing in population, we recommend checking the fields more often – twice per week.”

Knodel urges producers to follow correct scouting protocols and to use economic thresholds to make spraying decisions. “Since sunflower is a favored crop used for pollinators, we try to mitigate insecticide spraying and encourage farmers to spray only when it’s necessary by using these thresholds.”

Economic thresholds take many factors into account, such as the crop’s market value, plant stand, pest density and cost of insecticides. In addition, although many insects can be found in sunflower crops, most of them are beneficials and not pests, says Knodel.

Furthermore, populations cycle, she says, so they’re not always high for all insects. Weather conditions also determine if an environment is favorable for a particular pest. Another factor that affects population size is how successfully an insect has overwintered.

“It’s really important to scout because we can’t forecast whether or not a certain insect is going to be a big problem that year,” says Knodel.

IPM employs biological, cultural, physical and chemical tools to manage pests. Using IPM strategies are not only beneficial for the environment and the organisms living within it, but are also advantageous for producers in terms of costs savings and resistance management.

“The IPM grower may never have to spray because insects may not reach threshold levels. We only want to use our tools in our IPM box when we need to, so we don’t overuse them and potentially develop insecticide resistance. Plus, if you’re spraying, and you don’t have to, there are a lot of beneficials out there that feed on the eggs and immature stages of insects,” says Knodel.

“If that farmer didn’t have to spray because the populations are naturally low, he’s allowing the natural enemies, who are always out there in the field, to do their part in reducing the overall populations for next year,” she says.

NDSU Pest Management resources

Pesticide Resistance

More than 500 different insects have developed resistance to insecticides worldwide, says Dr. Janet Knodel, an extension entomologist and professor at North Dakota State University. Pyrethroid resistance is on the rise partly due to repeated use of the same insecticide year after year and not using economic thresholds to make insecticide application decisions.

There are a number of pyrethroids used to control insects in sunflower crops; however, resistance to one pyrethroid is resistance to all pyrethroids because they’re all the same mode of action, says Knodel.

“We call this cross resistance. There is hope though; we can control resistance in insects. We’ve done it before, we can do it again. Just rotate your insecticide modes of action and use a higher rate so that we don’t develop resistance.”

Knodel says other tips to lower the risk of insecticide resistance include:

  • Avoid using the same mode of action (or insecticide class) year after year
  • Avoid using the lowest labeled insecticide rate
  • Do not use premix insecticides containing two insecticides of the same or two different modes of action because premixes have lower amounts of active ingredient per insecticide
  • Optimize insecticide application by spraying during low winds and avoiding inversions
  • Use alternative IPM strategies

It’s important to report suspect cases of insecticide resistance. In North Dakota report suspect cases to a NDSU extension entomologist (Janet Knodel or Patrick Beauzay) or local county extension agent or crop specialist at Research and Extension Centers. In South Dakota report suspect cases to South Dakota State University extension field crop entomologist Adam Varenhorst.