Regional monitoring of whiteflies, Bemisia sp., in the lower Rio Grande Valley of Texas was undertaken between 1991 and 1995 to determine seasonal abundance and spatial population dynamics of this pest. Samples of whiteflies were taken using yellow sticky traps along roadways and samples from plants at selected locations. The abundance of parasitoids of whiteflies was quantified from each plant sample by species. The number of whitefly adults on yellow sticky traps consistently increased dramatically during late spring and summer and declined in the fall. Dispersion of whiteflies on sticky traps generally changed from highly clumped in the spring to less clumped in the summer and early fall of each year. The population of the native parasitoid complex of the whitefly correlated with increases of whitefly populations. Six whitefly parasitoid species were collected routinely and identified during this survey. In order of decreasing abundance they were Eretmocerus sp., Encarsia pergandiella, Encarsia meritoria, Encarsia sp. nr. strenua, Encarsia lutteola , and Encarsia formosa . Population levels were higher for whitefly and lower for whitefly parasitoids in 1995 than observed in 1994.
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Riley et al. (1997) studied this question.