Why should we care about insecticide resistance and what to do about it?Insect Ecology in Controlled Environments The Ohio State University/OARDC, Wooster canas.4@osu.edu Have you ever heard about insecticide resistance? I am sure you have, and if not, you will soon since it seems to be one of those current hot topics. But why should you care? There are different reasons why this should be important, but one of them is economics. When we use pesticides we want to be as effective as we can with the resources we have available. Not doing enough to prevent the development of insecticide resistance can in the end hurt your wallet. What is insecticide resistance? Insecticide resistance implies the loss of susceptibility to an insecticide. Therefore, we are not as successful as before in controlling insects because some of them survive, reproduce, and pass the genes that confer resistance. Currently we have a wide array of effective pesticides that can be used to control pest in ornamental plants, be it in greenhouses or in other settings. Continued usage of the same product means we are putting pressure on the insect population to develop resistance. How is this possible? Let's imagine we begin with 100 insects (i.e. whiteflies) and we decide to use one particular insecticide and end up killing 95 of them. The other 5 survive for various reasons, but let's assume that they do so because they were resistant to the insecticide (some insects already have the genes to be resistant to various compounds). Those 5 individuals (whiteflies) reproduce and pass along their resistance genes and we end up having more organisms that are resistant to the insecticide used. What happens if we spray again the same insecticide? Under this scenario the insecticide in question will not be as effective, which means you would need to spray more often, costing you more money. While this scenario overly simplifies a very complex process (development of insecticide resistance) it puts into perspective the necessity to use various techniques to control pests, but more importantly it stresses the need to minimize the development of resistance. While combining different control techniques (i.e. cultural and biological control with appropriate pesticides) is probably the best way to minimize the development of resistance, we can try to minimize the impact of successive applications by rotating products belonging to different mode of action groups. One important distinction now is that we need to rotate products that belong to different mode of actions group as stated by the Insect Resistance Action Committtee (IRAC, http://www.plantprotection.org/irac/ ). Previous recommendations had suggested that it would be sufficient to rotate insecticides belonging to different classes, but current research has suggested that it is necessary to rotate products belonging to different mode of action groups. As you can see from the list in TABLE 1 , some insecticides from different classes belong to the same mode of action group (i.e. Orthene is an organophosphate while Mesurol is a carbamate and both belong to mode of action group # 1). Therefore, after following the recommendations for control of a certain pest, you should pick insecticides that belong to different mode of action groups to develop an appropriate rotation. |
