Effects of plant growth regulators on survival and fitness of the oleander aphid, Aphis nerii (Homoptera: Aphididae), and the citrus mealybug, Planococcus citri (Homoptera: Pseudococcidae)

Treatment of plants with plant growth regulators (PGRs) has been found to affect populations of certain plant feeding insects. Differences in pest population density were shown either when a PGR was applied in combination with an insecticide or by itself. Objective of the present study was to evaluate the effect of chlormequat chloride, daminozide and prohexadione-calcium on the oleander aphid and the citrus mealybug survivorship. Nerium oleander and Viburnum odoratissimum plants, about 40 cm in height, were treated with high nitrogen fertilizer levels in the substrate and then sprayed twice biweekly with either chlormequat chloride, or daminozide or prohexadione-calcium. Plants that were not sprayed with PGRs were used as controls. No other chemical compound had been applied to the plants for several months prior to use in the experiments. Fully expanded leaves were collected from treated and control plants, the day after the second PGR application, and placed in petri dishes containing dumped cotton. One newly emerged first instar nymph of oleander aphid and citrus mealybug taken from stock colonies was caged in petri dish with oleander and viburnum leaves respectively, and it was checked daily for ecdysis and survival. Furthermore, one newly emerged female adult from each species from the same colonies was also caged in petri dish with oleander and viburnum leaves and it was checked daily for survival and nymph / egg laying. Ten replicates were used in each plant growth regulator treatment, plus ten replicates which served as untreated control. Results will be presented and discussed.