[The biological control of the European corn borer (Ostrinia nubilalis)]
1987
Stein, E. (Regierungspraesidium Freiburg (Germany, F.R.). Pflanzenschutzdienst)
The commercial use of Trichogramma evanescens in 1978-1986 in the southwest of the State of Baden-Wuerttemberg has proofed to give good control of the European corn borer. In twenty field trials of the plant protection service of Baden-Wuerttemberg in 1984-1986 the average effectiveness of the parasite in reducing the number of Ostrinia-larvae was 63 per cent. The biological control was compared with chemical treatments. The sprays were applied when the corn was approximately 1 m high. Treatments with the insecticide Decis (0.5 l and 0.7 l per ha) and with1667 the insecticide Ambush (0.36 l per ha) gave 67.7 l and 42 per cent control. During the trials there were great differences in the effectiveness of the biological treatments caused by differences in the dose of released parasites, in the parasitization rate of the host eggs and in the time of application. These problems are discussed and recommendations for improvement are given. The results of the trials indicate that good efficiency can be obtained by releasing at least 150.000 parasites per hectare. Two treatments (75.000 parasites per ha) using different developmental stages are sufficient. The first rate should be released at the beginning of the adult flight and prior to the oviposition of the European corn borer. The emergence of the adult parasites should begin soon after relea
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