Pesticides are an integral part of agriculture. They play an important role in making sure that we have enough food. Resistance to those pesticides is becoming a growing issue too. Let’s talk about what pesticide resistance is, how it occurs and what can be done to slow down resistance.
Pests are pretty smart and capable of adapting so that they continue to survive. Many different types of pests from diseases to insects to weeds are capable of becoming resistant to pesticides that are used to control them. When a pest is resistant that means the pesticide, whether it’s an herbicide, fungicide, or insecticide is no longer effective at controlling that pest population. Spraying a resistant pest is like spraying it with water. If a single pesticide is used repeatedly then you are creating a scenario where pesticide resistance is very likely to occur.
Let’s use aphids as an example for how resistance can occur. Aphids are a very common insect that is very small. They are capable of reproducing very quickly, which means they can become resistant to pesticides very easily. If you have an aphid problem and you decide to spray, that spray probably won’t be 100% effective at controlling the population. It’s somewhat similar to people in that not all medication is going to be equally effective for everybody. Those aphids that survived the application will continue to reproduce, passing the genes that gave them resistance down to their children. Before too long you may have an entire population that is resistant to that particular pesticide. Pests that reproduce quickly are more adept at developing pesticide resistance.
There are a few ways that pests can become resistant. The first is metabolic resistance. Some pests develop the ability to break down the pesticide once it’s been applied and they have taken it in. Again, this is similar to people who have a very fast metabolism so they never gain weight. These pests are able to take the pesticide and break it down so that it’s deemed ineffective before it can take effect. Another way that it can happen is that the target site of the pesticide in the pest is altered so that the pesticide is not able to take effect. Some insects develop thicker shells so that an insecticide can’t be absorbed. Simply altering behavior because pests are smart enough to avoid the pesticide can take place too. That is similar to when deer hunters remark that all the deer disappear when deer season opens.
Pesticide resistance can lead to a lot problems for producers. That’s why it’s important to remember to rotate modes of action. All labelled pesticides have a mode of action. The mode of action is the specific way that a pest is killed by the pesticide. If you use the same mode of action over and over, eventually you will have resistance to it. Rotating modes of action means that you keep switching things up on the pest, and so they will be less likely to become resistant. Pesticides have made it simple tell which mode of action you’re using by creating a number system. Each mode of action has its own number associated with it. If you rotate the numbers, you’ll rotate the modes of action.
Pesticide resistance is something that anyone who uses pesticides needs to be aware of. Some pesticides are going to be more susceptible to resistance than others are. Some pests are going to be more susceptible to resistance. If you have any questions about pesticide resistance, contact your local Extension Office or email me at Jacob.Williams@uga.edu.