Pymetrozine, a Fast-Acting and Selective Inhibitor of Aphid Feeding.In-situStudies with Electronic Monitoring of Feeding Behaviour

Abstract

: 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.

Insect TRP channels as targets for insecticides and repellents

“…Death from both of these insecticides is delayed and results from starvation as a consequence of inability to feed. [52][53][54] The first real clue to the mode of action of these insecticides was the observation that exposure of locusts to pymetrozine by feeding or injection caused them to hold their hind legs raised, with the tibiae extended (Fig. 1).…”

Compatibilidade de inseticidas e acaricidas com o percevejo predador Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) em algodoeiro

“…Embora não se tenha conhecimento de estudos de seletividade do pimetrozine para percevejos predadores, os resultados obtidos evidenciam-no como um produto em potencial para o manejo integrado de pragas, pois não causou mortalidade significativa nem afetou a taxa de predação de P. nigrispinus. É considerado específico para homópteros, com efeito de paralização da alimentação e morte dos insetos em um a três dias (Harrewijin & Kayser 1997). Em algodoais no Texas, Estados Unidos, a utilização de pimetrozine, seguida de aplicações de lambdacialotrina na formação da maçã, reduziu significativamente a população de pulgões (Slosser & Rummel 1998).…”

Impact of Reduced-Risk Insecticides on Soybean Aphid and Associated Natural Enemies

“…Pymetrozine (FulÞll, Syngenta Crop Protection, Inc., Greensboro, NC) was included based on its novel mode of action (paralysis of the cibarial muscle) that subsequently prevents feeding in the hemipteran suborder Sternorrhyncha (Harrewijn and Kayser 1997, Wyss and Bolsinger 1997b, Sechser et al 2002, Torres et al 2003, Banks and Stark 2004. In addition to its selective mode of action, pymetrozine is plant systemic (symplasticly mobile) that results in a further reduction in exposure to nontarget organisms.…”