Effects of plant architecture on the attack rate of Leptomastix dactylopii(Hymenoptera : Encyrtidae), a parasitoid of the citrus mealybug (Homoptera: Pseudococcidae)

Attack rates of the parasitoid Leptomastix dactylopii (Howard) were examine d in petri dishes and on caged plants that varied in architectural characte ristics. Individual female parasitoids were placed into petri dishes contai ning a range of densities of the citrus mealybug, Planococcus citri (Risso) . Green and yellow-variegated coleus, Solenostemon scutellarioides (L.) Cod d, were used to determine the effects of plant architecture on the rate at which L. dactylopii parasitized citrus mealybugs. Coleus plants were catego rized into size classes based on height, number of leaves, leaf surface are a, and number of branches. A single mated female L. dactylopii was placed i nto each plastic observation cage containing a plant with 1, 8, or 16 third - to early fourth-instar mealybugs and allowed to forage for 24 h. After th is time, citrus mealybugs were removed from coleus plants and placed into p etri dishes that were checked after 10 d for mummified citrus mealybugs, th e measure of a successful attack. L. dactylopii were unable to find a host after 24 h when only one citrus mealybug was present in the searching envir onment. Higher attack rates occurred as the number of mealybugs increased i n the petri dishes. L. dactylopii attacked an average of 15.6 +/- 2.3 mealy bugs within a 24-h period. Higher attack rates were evident as the number o f citrus mealybugs increased on caged plants. Plant color had no effect on the attack rate of L. dactylopii. All architectural characterizations of pl ant size, height, leaf number, leaf surface area, and branch number were ne gatively correlated with parasitoid attack rate. These Endings suggest that biological control practitioners may use any convenient measure of plant s ize (e.g., height) to modify the release rate of L. dactylopii in a citrus mealybug management program.