Nursery, Greenhouse, and Landscape News

Importance of Leaf Spines on Poinsettia to Silverleaf Whitefly Natural Enemies

Two cultivars of poinsettia were examined in the laboratory to determine if they affected the ability of natural enemies to kill silverleaf whitefly. 'Annette Hegg Brilliant Diamond' has about 15% fewer leaf hairs (trichomes) on their leaf undersides than did 'Lilo'. Trichomes have been shown to reduce the effectiveness of natural enemies of greenhouse whitefly on other crops. Five natural enemies tested (the predaceous lady beetle Delphastus pusillus, and the wasps Encarsia luteola, E. formosa, E. pergandiella, and E. transvena) were able to kill more whiteflies on the cultivar with fewer trichomes. These trichomes seem to interfere with the ability of the natural enemies to capture and kill silverleaf whiteflies. Two of these natural enemies, Delphastus pusillus and Encarsia luteola, were used successfully to control silverleaf whitefly in a commercial greenhouse on 'Freedom' poinsettia, but no information was reported on the number of leaf trichomes on this cultivar.

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