For Release June 20, 2000

How To Prevent Pesticide Resistance

AGRI-VIEWS
by Chuck Otte, Geary County Extension Agent

Last week I discussed how pesticide resistance occurs. In a nutshell, we destroy all the susceptible population and all that’s left to reproduce are the ones who were resistant to the pesticide. Pesticide resistance can occur anywhere. They can occur over a broad area, they can occur in your own backyard.

When an organism becomes resistant to a pesticide, it does not necessarily become resistant to ALL pesticides. A Roundup tolerant soybean, is still going to be killed by 2,4-D. 2,4-D and Roundup are herbicides that have different modes of action. They are in different families. Two commonly used insecticides, diazinon and Malathion are both in the group of insecticides that we call organophosphates. They are closely related and they control insects in the same basic manner. If an insect pest in your garden becomes resistant to diazinon, they are probably going to be resistant to Malathion also.

Pesticide resistance does not move easily between species. If you have a Roundup tolerant soybean plant, it is not going to transfer that trait to a cocklebur plant. They are two different species and do not naturally cross pollinate. The Roundup resistant trait can not just "hop across" to the cocklebur plant because they are growing close to each other.

However, if you had a Roundup tolerant sunflower crop or grain sorghum crop, you could have problems. Since the domestic sunflower and the wild sunflower are so closely related, you could see a transfer of the resistant gene. Since shattercane is nothing more than volunteer grain or forage sorghum, the a Roundup resistant shattercane population could very easily arise from Roundup ready hybrid grain sorghum. Talk about a mess!

To reduce the risk of a pesticide resistant population developing, we have to make sure that there are an adequate number of pesticide susceptible survivors. We want to keep the susceptible genes more common in the wild population than the resistant genes. We need to be a little bit sloppy in our pest control.

Federal law requires that only a certain percentage of a producers corn acreage be planted to BT hybrids. There has to be a certain percentage of non-BT corn refuge in every field. Sure, we’re going to suffer some insect damage in those acres, but that allows susceptible insects to stay viable in the population.

While not a federal law, I encourage producers to rotate crops AND herbicides in fields. If you are constantly using the same class of herbicide in the same field, you will develop problems. Mix tillage in with herbicide applications. I’ve yet to see a weed develop resistance to a cultivator or a hoe! Mix up pre-emerge herbicides with a different class of post-emerge herbicides. And if you miss a couple of rows on the edge of fields, so what? Consider it a refuge.

The same concept applies around home. If you are spraying for problems, especially large population insects with fast reproductive rates, like aphids or mites, use different classes of insecticides. Instead of using a herbicide for all your garden or lawn weed control try pulling a few weeds or using a hoe.

Pesticide resistance will happen, given enough time. It’s not a failure of the pesticide, though. Rather, it is a failure of our management. Technology never has, and never will, replace good management!

-30-

Return to Agri-Views Home Page

Return to Ag Home Page