Control of gypsy moth, Lymantria dispar L. (Lepidoptera: Lymantriidae), with a nuclear polyhedrosis virus by treatment of egg masses, and identification of the effective NPV strain by REN analysis
1988
Trzebitzky, C. (Forstliche Versuchs- und Forschungsanstalt Baden-Wuerttemberg, Freiburg (Germany, F.R.)) | Bogenschuetz, H. | Huber, J. | Lohmann, K.
Field collected egg masses of the gypsy moth, Lymantria dispar L. were sprayed in the laboratory with different concentrations of a nuclear polyhedrosis virus (LdMNPV). The LC90 for the larvae hatching from the eggs averaged 2.7 x 10(7) polyhedra/ml after 12 days at 25 degrees C. In a field trial in April 1986, gypsy moth egg masses in a forest in the Upper Rhine Valley near Kehl (FRG) were sprayed from the ground with NPV-suspensions containing sugar and a commerical sticker. 2 ha (egg mass density 2300 egg masses/ha) were treated with 10(7) P/ml and 2 ha (1400 masses/ha) with 10(8) P/ml. 7 ha were left untreated and served as a control plot. Every week, samples of larvae were collected in the 3 plots and reared in the laboratory. 6 weeks after the virus application, NPV-induced mortality reached 40 to 60 per cent for the samples of the treated as well as the untreated plots. Dispersal of virus infested young larvae by wind probably spread the virus from treated plots to the adjacent control plots. Overall mortality of the larvae (including death due to parasites) amounted to 80 - 90 per cent weekly. The reduction in egg mass density at the end of the season was over 99 per cent, i.e. the population collapsed. Since in other locations of the same area gypsy moth suffered from natural NPV infections, the identity of the virus in the experimental plots was verified by restriction endonuclease analysis of viral DNA from field collected diseased larvae. The virus from the treated plots and from the control was identical to the NPV from the preparation used in the treatment, whereas virus from another location was distinctly different in its DNA profiles
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