Effects of the plant growth regulator prohexadione – calcium on survival of the Asian citrus psyllid (Diaphorina citri)

Application of plant growth regulators (PGRs) has been found to affect populations of certain plant feeding insects. In past studies, there were differences in the population density of pests when a PGR was applied in combination with an insecticide or by itself. This could be explained due to the better canopy penetration and coverage by pesticides or due to the reduced ovipositioning sites on the tree, both a result of reduced plant growth. In previous studies, prohexadione-calcium, a plant growth regulator that inhibits gibberellin metabolism, resulted in reduced populations of insect pests, when used individually or in combination with imidacloprid in pear and apple. The objective of the present study was to evaluate the effect of prohexadione-calcium on Asian citrus psyllid survivorship when used individually or in combination with imidacloprid. Three treatments were applied to single-tree plots of sweet orange in a completely randomized design. Trees used were ‘Valencia’ sweet orange which had not been treated with any other chemical compound for several months prior to use in experiments. Fully expanded "old" leaves were collected from treated trees the day after applications were made and then again 7, 14 and 21 days later. A cork borer was used to cut leaf disks from the collected leaves. A pair of psyllids was caged in each petri dish with four disks of same treated leaves and they were checked daily for survival. Results will be presented and discussed.