The effect of subfreezing temperatures on survival of Bemisia tabaci MEAM1

Abstract

The sweetpotato whitefly Bemisia tabaci is a destructive pest on a wide variety of agricultural crops. Whiteflies are managed largely through the use of insecticides, but B. tabaci has developed tolerance or resistance to a broad range of active ingredients. Identifying events where insecticide applications could be delayed or eliminated may mitigate insecticide resistance. One such event is cold weather, which can decrease whitefly activity including dispersal and mating, or kill a substantial proportion of the whitefly population when temperatures fall below freezing. The objective of this research was to quantify the effects of exposure period to subfreezing temperatures on the mortality of adult whitefly. Results showed that whitefly mortality could be predicted through a non-linear function of a composite variable of temperature and exposure time (x). This model was applied retroactively to six seasons of field data collected in southwest Florida during the months of November through February. Based on observation and model output, significant drops in the whitefly population were mostly associated with two or more cold events – separated by no more than 7 days – with at least one of those events with x > 13. Moreover, the decrease was sustained for 4–6 weeks after the last event. The ability to predict decreases in the whitefly population in response to freeze events gives growers the opportunity to relax insecticide schedules, particularly in the spring cropping season, with high confidence that their crop is at low risk to whitefly damage.