Untersuchungen zur Wirkung von Imidacloprid auf Getreideblattlaeuse und deren Effizienz zur Uebertragung des BYD-Virus.
1992
Knaust H. J. | Poehling H. M.
The active ingredient imidacloprid used as seed dressing did not bring about rapid extermination of the species Sitobion avenae, Rhopalosiphum padi, and Metopolophium dirhodum under laboratory conditions. Imidacloprid exerted a prolonged effect (over 6 weeks after sowing) against wingless S. avenae adults, reducing the duration of survival, secretion of honeydew, and fertility of the pest in oats and winter barley. As a secondary effect, it led to the production of undifferentiated embryos and fewer larvae. In the sublethal range (no acute action on adults) the active ingredient achieved an almost constant high level of larval mortality. Despite the fact that feeding activity was in some substances interrupted many times, repellent and deterrent effects were excluded with the aid of a choice study. The efficacy is probably due to neurotoxic rather than to late antifeedant effects. Winged or wingless aphids transferred daily from treated plants (equivalent, in outdoor conditions, to ones which have migrated) were mostly able to infect a plant (generally the first one) with BYDV. In contrast to the controls, only a small percentage of individuals still alive after 24h were able to infect further plants. Extrapolation of the results to outdoor conditions shows that imidacloprid prevents secondary spread of aphids in particular, thus also preventing virus disease. Field studies in oats (summer 1991) and winter barley (autumn 1991) have confirmed the laboratory results, demonstrating the emerging cereals can be given prolonged protection from aphids and from infection with BYDV. In oats, an application rate of 105 g a.i./dt allowed control of aphids even during the flowering stage. Rhopalosiphum padi was reduced particularly drastically.
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