Control of Silverleaf Whitefly on Poinsettia, 1995

One hundred and forty-four Poinsettia cuttings were planted in 6 inch pots and grown in a silverleaf whitefly-infested greenhouse compartment at the Ohio Agricultural Research and Development Center, Wooster, Ohio. Plants were fertigated using 250 ppm 15-16-17 on a 3 fertilizer:l leach schedule. On 7 September 1995, when the plants were 11 wk old, treatments of two systemic insecticides were applied at a range of rates, separately and in combination. Applications were weighed out on a Sartorius balance and poured onto the soil surface from plastic spoons. The plants were watered following the application. Twelve treatments were applied to four plants in each of three replicates of a completely randomized design. Each replicate occupied a separate bench in the compartment. Pre-treatment counts were made immediately prior to the treatments; post-treatment counts were made 14 and 45 DAT. Adult whitefly were sampled by counting on 2 upper, 2 middle and 2 lower leaves of each plant. In addition late instars were sampled at 45 DAT by binocular microscope examination of 2.5 cm leaf disks removed from 2 upper, 2 middle and 2 lower leaves from each plant. Temperature and humidity were 25±5 °C and 60±25 %RH during the trial.