Impact of Harmonia axyridis (Coleoptera: Coccinellidae) On Native Arthropod Predators in Pecan and Crape Myrtle

Russell F. Mizell III

Abstract


Harmonia axyridis (Pallas) was first detected in north Florida in 1993 feeding on crape myrtle aphids, Sarucallis kahawaluokalani (Kirkaldy) on crape myrtle, Lagerstroemia indica L. This lady beetle spread rapidly and was instrumental in reducing populations of the yellow pecan aphid complex, Monellia caryella (Fitch) and Monelliopsis pecanis Bissell, in pecan as well as crapemyrtle aphids. Prior to the arrival of H. axyridis to north Florida, the population dynamics of the yellow pecan aphid complex were compared to those of the crapemyrtle aphid and their common arthropod predators. The current study, conducted 8 and 9 years after the arrival of H. axyridis, sampled the same locations and some of the same trees reported previously. This research compares the current aphid and arthropod predator populations with the earlier results to determine the impact of H. axyridis. Prior to the addition of H. axyridis, aphid populations achieved high numbers and the lady beetles, Hippodamia convergens (Guerin-Meneville), Olla v-nigrum (Mulsant), Coleomegilla maculata (DeGeer), Cycloneda sanguinea L. and C. munda (Say) were the most frequently observed predators. In 1984-1985, other common predators included the green lacewing, Chrysoperla rufilabris (Burmeister), the brown lacewings, Micromus posticus (Walker), and Hemerobius stigma (Stephens), the mirid, Deraeocorus nebulosus (Uhler), the reduviids, Zelus exsanguis (Stahl) and Sinea spinipes (Herrich-Schaeffer), the hover flies, Allograpta obliqua (Say) and Mesograpta sp., the anthocorid, Orius insidious (Say), and spiders. A parasitoid of pecan aphids, Aphelinus perpallidus Gahan, was also common. Recent sampling showed H. axyridis to be the dominant predator of aphid populations. Populations of the aphids and the native predator and parasitoid species are dramatically reduced. Only spiders and the reduviids, species potentially involved in intraguild predation with H. axyridis, were detected.

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