Bekämpfungsversuch gegen Eucosma griseana (Hübner) (Lepidoptera, Tortricidae) mit einem Granulosis-Virus

Birmensdorf

1957

S. 73-93

8 Abb., 8 Tab., 11 Lit. Ang.

Bandaufführung

157670

The first attempt to control the larch bud moth in the field using a granulosis virus was made in 1955. This experiment was part of the team work undertaken to study the population dynamics of this insect in the Engadin. In the present paper the method of treatment is described and the results are discussed. The tests were conducted in three different areas of the Engadin, each characterized by a high density of the larch bud moth population. In each plot two larches were sprayes with virus suspension and four more trees were selected as controls. A portable atomizer was used for the application of the virus suspension. Variations in the population densities of larvae both on the treated and on the control trees were established through the following 18-21 days. The results were contrary to expectation. Reduction in the population density an the treated trees was not higher than that on the control trees. On four of the six treated trees this reduction was even less than that on the corresponding control trees. For the present, the cause of this phenomenon remains unknown. These results are published in order to show that certain methodological aspects of basic importance in the microbial control of this insect by means of virus (dosage of virus, technique of application, population susceptibility to granulosis, and the timing of treatment in relation to the development of the larvae and the phase og the oscilliation) still have to be thoroughly investigating before attempting a large scale experiment. In our special case, additional investiations will have to prove to what extent the virulence of the virus sprayed on the larch needles is affected by the ultra-violet rays at these elevations of 4700-5900 feet.