Pymetrozine, a Fast-Acting and Selective Inhibitor of Aphid Feeding. In - situ Studies with Electronic Monitoring of Feeding Behaviour
✍ Scribed by Harrewijn, Paul; Kayser, Hartmut
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 278 KB
- Volume
- 49
- Category
- Article
- ISSN
- 1526-498X
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✦ Synopsis
Pymetrozine, a pyridine azomethine compound, represents a novel insecticide with a selective activity against homopteran insects. It acts in a unique way : aphids are not knocked down on contact but seem to die of starvation. This implies an e †ect of pymetrozine on feeding behaviour. The aim of the present work was to elucidate how and at which step pymetrozine interferes with the complex mechanisms underlying phloem feeding. The e †ect of pymetrozine, applied in various ways, on di †erent phases of stylet penetration and feeding activity of individual aphids was studied using the Electrical Penetration Graph technique (EPG). Initial choice experiments indicated that pymetrozine does not have a deterrent or antifeedant action. Topical application (150 ng pymetrozine mg~1 fresh weight) inhibited stylet insertion into the plant. When injected, less than 30 ng mg~1 was sufficient to produce the same e †ect. When pymetrozine was systemically applied via plant spraying or root uptake, aphids started feeding normally. After some time, however, they withdrew their stylets from the phloem and walked around with una †ected locomotion. At low doses aphids eventually recovered and resumed feeding. High doses, however, irreversibly disrupted feeding and prevented stylet reinsertion. Aphid motility was not a †ected up to an estimated haemolymph concentration of 1 mM pymetrozine. Aphids which eventually stopped feeding on pymetrozine-treated plants showed EPGs with distorted salivation/ingestion patterns. It is concluded that pymetrozine does not have a general toxic e †ect on aphids but selectively interferes with the nervous regulation of feeding behaviour which consequently results in death due to starvation after a few days.