Nursery, Greenhouse, and Landscape News

Biological Control of Silverleaf Whitefly on Commercial Poinsettia

Commercially acceptable control of silverleaf whitefly (formerly, type B strain of sweetpotato whitefly) was achieved on Poinsettia using the parasitic wasp Encarsia luteola in conjunction with the predaceous lady beetle, Delphastus pusillus. One Encarsia luteola was released per plant for 3 weeks after silver leaf whitefly was detected in the greenhouse in early September. After immature whitefly nymph numbers escalated in late October, one Delphastus pusillus was released per plant for three weeks. At harvest, in early December, the number of whitefly nymphs on these plants was compared to that on untreated plants and those receiving chemical treatments (2 sprays of kinoprene and 6 sulfotep fumigations). Both chemical treatments and natural enemies reduced whitefly numbers by about 75%. This research also demonstrates that Delphastus pusillus can be used effectively with parasitoids of whiteflies in a commercial situation. Cost comparison showed that biological control was achieved at five times the price of chemical control. However, the costs of biological control can be expected to come down in the future as the costs of natural enemy production decreases with improved technology. Furthermore, the benefits of using biological control in terms of worker safety and the reduced impact of worker protection standards were not accounted for in this cost comparison.

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