Nursery, Greenhouse, and Landscape News

Performance of Five Silverleaf Whitefly Natural Enemies on Poinsettia

Five natural enemies of silverleaf whitefly (the predatory lady beetle Delphastus pusillus and four wasp parasitoids, Encarsia luteola, E. formosa, E. pergandiella, and E.transvena) were evaluated in the laboratory to compare their relative ability to kill whiteflies on poinsettia. Of these species, D. pusillus killed the most whiteflies, owing to its voracious appetite and longevity. In contrast to previous reports on cotton, D. pusillus would lay eggs if fed a diet of only silverleaf whitefly nymphs and no eggs. This suggests that these beetles might be more likely to reproduce in a commercial greenhouse than previously thought. However, this beetle will still be most effective at higher whitefly densities because they require large numbers of prey to reproduce.

Of the parasitoids, E. formosa originating from a greenhouse whitefly colony on poinsettia, and mated E. pergandiella had the greatest potential to kill silverleaf whitefly, because they live longer than other species. Differences found between these closely related parasitoids suggest that growers need to be selective when choosing parasitoid species for a biological control program. Simple reports that they attack and reproduce on a pest are not enough. The colony history of the natural enemy can have a profound impact on natural enemy effectiveness. The performance of Encarsia formosa reared from greenhouse whitefly for many generations on poinsettia was far superior to that of those from tobacco-grown greenhouse whitefly. Not only did the wasps live more than twice as long on poinsettia-grown silverleaf whitefly, they can also parasitize more individuals.

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