Insecticide Resistance Management

Grady J. Glenn*

Pesticide resistance is the adaptation of followed in a relatively short period of pest populations to the treatment of a time by cases of resistance to them. pesticide which results in a decreased susceptibility. The idea of Insecticide The development of resistance to Resistance Management (IRM) is pesticides is having an influence considered to have a current emphasis, on applicators, whether they are yet the concept was described as long working to protect agronomic and ago as 1914 by A. L. Melander in row crops, working in vector discussions of the resistance of Scale control, or in urban pest insects to insecticide treatments. It is an management. A coalition of important concept because the industry, research, and regulatory consequences are extremely serious, groups has formed the since insecticides often offer the only Insecticide Resistance Action effective means of management when Committee (IRAC) to respond to pest populations reach high numbers. the problems associated with resistance. http://www.irac-online.org/ The development of synthetic organic insecticides such as DDT was promising Economic consequences of because of their attributes. They were resistance can be profound, effective, relatively inexpensive, and particularly when insecticide were broad spectrum in their effects on applications are increased and insects. DDT was first utilized in 1939, more and stronger insecticides but resistance to the insecticide was are applied to overcome documented by 1947. Long-term resistance in pest populations. negative effects observed on wildlife Environmental consequences resulted in a ban of DDT by 1972. Each must also be considered in the subsequent introduction of a different scenario when treatments must be class of insecticides, from chlorinated done more frequently or at higher hydrocarbons, organophosphates, concentrations in situations where carbamates, and pyrethroids was insecticides become less effective. These treatments lead *Texas AgriLIFE Extension Service Specialist

to increased opportunities for How does insecticide resistance develop? contamination of soil, air, and water. Insect pest populations develop resistance because of a number of There are many examples of factors and influences. (1) Insects, in insect species developing general, are capable of producing a resistance to widely used large number of offspring, and with this insecticides. Resistance in capacity is the increased opportunity of Whitefly populations in cotton in mutations leading to resistance. (2) Arizona in the 1990’s caused a Most insects are inherently exposed to 12-fold increase in chemical natural toxins in their respective food control costs over a five year sources, with the subsequent period, and the number of development of physiological capacity to insecticide applications went from detoxify chemicals encountered in the two per season to as many as a environment. (3) The heavy reliance on dozen. Before the introduction of insecticides for pest management by the new mode of action of applicators increases the selection neonicotinoid insecticides, a pressure and can result in resistance, similar scenario of resistance particularly when insecticides with the occurred in Whiteflies feeding on same mode of action are applied. ornamental plants. An example of this development of resistance in an insect is the story of the bedbug. The resurgence of bedbugs has made headlines in the press recently. There are many factors that have contributed to the increased observation of these insects worldwide, including increasing international travel and the reduced use of insecticides in sleeping areas of residences, hotels, homeless shelters, and hospitals. It should come as no surprise that bedbug populations are resistant to the current IRAC has estimated that additional group of insecticides being used against treatments and alternative controls them. Organophosphate insecticides increases the total insecticide costs to such as Diazinon and Chlorpyrifos are tens of millions of dollars, nationwide. no longer allowed to be used in urban This has fueled fears that our current pest management, leaving pyrethroids insecticide tools can be made ineffective as the tools of choice. The pyrethroids unless new alternatives are developed. are in the same mode of action category  Leave untreated population as was DDT (Group 3: Sodium channel refuges where susceptible modulators), which was the primary pests can survive and insert treatment insecticide used in earlier their genetics into populations campaigns to eradicate bedbugs.  Alternate insecticides with a different mode of action (See IRAC)  Apply insecticides in tank- mixes or sequentially that include multiple modes of action  Utilize host-plant resistance and rotate to different crops

 Improve sanitation Bedbug feeding It is important to monitor pest populations regularly. Any changes in insect populations that may indicate the presence or development of resistance should be dealt with promptly, utilizing the strategies listed above. Another management strategy is to apply a lethal rate of an insecticide. It may be tempting for an applicator to reduce insecticide Early Bedbug Insecticide Treatment rates to decrease cost but this practice can contribute to resistance. One How do we manage these resistant chemical treatment with no documented insects? resistance is methyl bromide; the lethal nature of this fumigant gas results in In those areas that are currently affected zero survivors capable of passing on by resistant insect species, everyone resistance. must change their pest management strategies in order to delay the onset of Conclusion: or mitigate existing pest resistance. Some of these strategies include: Insecticide resistance will continue to be an issue, because resistance can never  Avoid unnecessary insecticide be halted. Utilizing an integrated applications; these place more resistance management plan allows us selection pressure on insect to delay and manage resistance. populations  Utilize non-chemical control techniques

This factsheet was developed through a grant provided by EPA Region 6 Strategic Ag Initiative.

Reviewers: Mr. Ples Spradley, University of Arkansas, Ms. Karen Nix, Louisiana State University Ag Center, Dr. Carol Sutherland, New Mexico State University, Mr. Charles Luper, Oklahoma State University, Dr. Don Renchie, Texas AgriLife Extension Service.