Author
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HAJEK, A - CORNELL UNIVERSITY |
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WEBB, RALPH |
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Submitted to: Biological Control
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 9/21/1998 Publication Date: N/A Citation: N/A Interpretive Summary: The gypsy moth caterpillar eats the leaves of shade trees around homes. In the past, effective control has meant aerial application of insecticides or ground application of insecticides using large power sprayers. Many homeowners prefer to use natural control agents if available. We evaluated a new tactic for controlling gypsy moths using a natural control agent. Specifically, we introduced small quantities of inoculum of a fungus, Entomophaga maimaiga, that causes a natural disease of the gypsy moth, around a small group of shade trees in small woodlots similar to those homeowner properties. We found that gypsy moth caterpillars in the woodlots receiving the inoculum died sooner from the fungus than did caterpillars in woodlots receiving no fungal inoculum. This in turn led to less defoliation in the treated plots. We thus demonstrated the feasibility of introducing E. maimaiga into gypsy moth populations under homeowner-like situations. Results should be useful to those seeking to control gypsy moth attacking residential shade trees using natural control agents, including homeowners and their advisors. Technical Abstract: Resting spores of the gypsy moth fungal pathogen Entomophaga maimaiga were introduced to four treatment plots on the eastern shore of Maryland in 1995 and 1996 to augment the naturally occurring fungal population. To evaluate results, larvae were sampled from the understory vegetation, under burlap bands, and in the tree canopy. For both years, survival of fifth and sixth instar gypsy moth larvae was significantly lower in treatment versus control plots on some sampling dates. Infection by E. maimaiga was always greater in treatment than control plots, but due to variability among plots, these differences were not significant. During 1995, severe defoliation occurred in only one control plot, and numbers of fifth instars were positively associated with defoliation level. During 1996, no defoliation occurred in any plot because of area-wide gypsy moth population collapse. This is the first study sampling gypsy moth larvae throughout the tree canopy to determine the relative distribution of larvae infected by E. maimaiga and the Lymantria dispar nuclear polyhedrosis virus (LdNPV). Third- through fifth- and sixth-instar gypsy moth larvae infected with E. maimaiga were more abundant in the understory vegetation than in the tree canopy. Larvae infected by LdNPV demonstrated a later season trend toward increased occurrence in the tree canopy, although results were not significant. |
