Control of Silverleaf Whitefly on Poinsettia Under Greenhouse Conditions, Fall 1996

Poinsettias, obtained as rooted cuttings, were planted in 15 cm pots and allowed 12 wk growth (30-40 cm tall) before use. The plants were fertilized once with Osmocote (14-14-14) and irrigated every other day for three minutes by drip system. Silverleaf whiteflies and a parasitoid, Encarsia formosa (Gahan), were present in the greenhouse as the plants grew. By the time we conducted the trial, the plants were moderately infested with whiteflies. A leaf near the top of the plant containing young nymphs and parasitized nymphs was chosen to monitor the efficacy of selected pesticides. A 2.5 cm diam circle was drawn on the abaxial leaf surface, and the number of live and parasitized whitefly nymphs were recorded. A pre-treatment count was taken on 10 Oct and was followed by the treatment application. A second treatment application was applied one wk later. Post-treatment counts of live, dead, and parasitized whitefly nymphs were taken weekly for two wks following the first application. Treatments were applied using a backpack sprayer at approximately 25 psi. A RCB design was used with 5 replicates per treatment. An ANOVA was performed on the data set, and Ryan’s Q (P = 0.05) was used to separate the means.