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

Raymond Allen Cloyd, Purdue University

Abstract

Green and yellow-leafed coleus plants, Solenostemon scutellarioides (L.) Codd, were studied to examine how variegation-mediated changes in plant architecture altered the attack rate of Leptomastix dactylopii (Howard) on its host citrus mealybug, Planococcus citri (Risso). Increases in height (cm), leaf number, leaf surface area (cm2), or branch number resulted in a decrease in attack rates whereas increasing the number of citrus mealybugs per plant resulted in higher attack rates. However, the low number of attacks and the relatedness of the plant architectural characteristics made it difficult to determine which characterizations of plant size were most important in influencing the foraging success of L. dactylopii. Observations were conducted on L. dactylopii in cages to associate attack rates with behavior. Leptomastix dactylopii behaviors were categorized based on mobility (moving and stationary) and location (plant and cage). Low attack rates made it difficult to directly associate these behaviors with attacks. The low attack rates by L. dactylopii may have resulted from the parasitoid requiring time to habituate to a new searching environment. These findings suggest that modifying rearing environments to condition natural enemies to target crops prior to release may increase natural enemy activity and performance. In addition, because all characterizations of plant size influenced the attack rate of L. dactylopii, biological control practitioners may eventually be able to use any convenient measure of plant size to adjust release rates of natural enemies.

Degree

Ph.D.

Advisors

Sadof, Purdue University.

Subject Area

Entomology|Agronomy|Ecology

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