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Biological control of viburnum leaf beetle 2001

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Project Leader(s): Paul A. Weston, Senior Research Associate, Department of Entomology, Cornell University, Ithaca, NY

Cooperator(s): Brian Eshenaur, Horticulture Extension Educator, Monroe Co. Coop. Ext., Rochester, NY

Jana Lamboy, Ornamentals IPM Coordinator, NYSAES, Geveva, NY

Type of grant: Biological control and pest biology

Project location(s): Northeastern U.S.

Abstract: The overall goal of this project was to evaluate field efficacy of several bioloigical control agents identified in the laboratory as having potential for biological control of viburnum leaf beetle, a recently introduced pest in the U.S. Although the pest can be controlled effectively with insecticides, biological control would be preferable for long term management and for limiting pest damage to susceptible plants in naturalized settings. We previously identified two generalist predators (Chrysoperla carnea and Harmonia axyridis) and a pathogenic nematode (Heterorhabditis bacteriophora) in laboratory trials that appear to have potential for controlling viburnum leaf beetle; in this project we tested these organisms to the field to see if their efficacy extended to this setting. In addition, we sampled soil near host viburnums in the field for the presence of endemic nematodes. Both species of predators significantly reduced the amount of damage sustained by the caged viburnums compared to the control. In the case of H. axyridis, the percent reduction was an impressive 75% or more. We were unable to ascertain the efficacy of the nematode because adult emergence from the plots was too low. Results from the soil sampling for nematodes was equivocal; the incidence of nematodes was very low, perhaps because soil moisture was rather low compared to 2000.

The results of this study indicate that augmenting populations of predators with commercially available insects, especially H. axyridis, may dramatically limit the amount of feeding by viburnum leaf beetle larvae on susceptible viburnums (and likely reduce adult populations by a similar extent since the larvae are being eliminated by the predator). Pesticides needed for control of the pest would be correspondingly decreased. Further evaluation is necessary, however, because the cages used in this study may have resulted in greater predatory efficiency since the predators were not able to leave the host plants. In addition, further field testing of the nematode is needed to determine what their efficacy might be under more typical conditions than those used in this study (e.g. utilizing ground covers or mulch).