|Ellsworth, Peter - UNIV OF AZ, MARICOPA|
|Prabhaker, Nilima - UNIV OF CA, RIVERSIDE|
|Toscano, Nick - UNIV OF CA, RIVERSIDE|
Submitted to: University of Arizona Agricultural Experiment Station
Publication Type: Experiment Station
Publication Acceptance Date: June 1, 2001
Publication Date: N/A
Technical Abstract: As part of a program to assess differences in susceptibility to insecticides among regional populations of Bemisia tabaci, insecticide resistance monitoring was carried out at the Maricopa Agricultural Center from fall 1995-1999. Monitoring efforts were concentrated on Danitol+ Orthene following reports t of control problems and documentation of resistance to this mixture in 1995. We were interested in the longer-term dynamics of resistance in light of radically altered treatment regimens beginning with the use of IGRs in 1996. Although the frequency of susceptible individuals to Danitol+Orthene tended to. increase in the later years, highly resistant individuals were still present 5 years after the resistance episode of 1995. Whitefly adults collected from various insecticide treatment plots other than Danitol+Orthene were generally uniform in their responses from the time of initial whitefly infestation until defoliation. However, a dramatic shift in susceptibility occurred following a single application of Danitol+Orthene in 1997 and 1999. The increased frequency of resistant individuals following treatment suggests that any large scale return to the use of Danitol+Orthene could rapidly select for proportionally higher numbers of resistant whiteflies and perhaps reduced control in cotton fields.