Genetics and Management of Resistance to Pyriproxyfen in the Whitefly Bemisia tabaci

Abstract

Selective insecticides such as insect growth regulators that kill pests but cause little or no harm to non-target organisms have become increasingly important in crop production systems worldwide. The insect growth regulator pyriproxyfen has been successfully used for the last decade in Arizona as part of an integrated pest management (IPM) program for the sweetpotato whitefly, Bemisia tabaci, a problematic pest in Arizona and other regions of the world throughout the world.A serious threat to the continued success of the IPM program in Arizona is the evolution of insecticide resistance in B. tabaci. To enhance the ability to design sound strategies for managing whitefly resistance to pyriproxyfen we: 1) compared susceptibility to pyriproxyfen between male and female B. tabaci; 2) determined the dominance of pyriproxyfen resistance; 3) determined if fitness costs were associated with resistance; 4) estimated the number of genes affecting resistance; 5) developed resistance management models.Laboratory and field bioassays investigated the genetics of pyriproxyfen resistance in males and females from a pyriproxyfen-susceptible and pyriproxyfen-resistant strain (>1000 fold resistance). Results showed that male and female B. tabaci did not differ in susceptibility to pyriproxyfen, resistance was partially to completely dominant under approximated field conditions, and fitness costs were not associated with resistance. Similar traits in field populations could threaten the efficacy of pyriproxyfen. Model results indicated that the current IPM program for B. tabaci could be improved by curtailing the use of pyriproxyfen in cotton-intensive regions, synchronizing the use of pyriproxyfen with key crop production stages in the field, and applying the lowest pyriproxyfen concentration needed to provide effective control.Knowledge generated from this research has provided insight into factors affecting B. tabaci resistance to pyriproxyfen, which could improve management strategies for B. tabaci in Arizona cotton and other crops. This project represents a proactive approach to understanding pyriproxyfen resistance and its potential impacts before resistance evolves to problematic levels in the field. In addition, the project provided insight into mechanisms affecting resistance in a haplodiploid pest. Thus, the research can serve as a model for basic research on other haplodiploid pests.