PLANT-MEDIATED EFFECTS ON PYMETROZINE EFFICACY AGAINST APHIDS

The influence of plant factors on the efficacy of pymetrozine (CGA 215 944), an insecticide against homopteran pests, was investigated. Amon g all parameters tested, plant species was found to influence pymetroz ine activity most. Differences in the compartmentation of pymetrozine within tissues of different plant species were found: 33% of extractab le compound was measured in the intercellular space of tomato leaves, but only 5% in the same compartment of sugar beet leaves. Foliar uptak e after spray application was around 5% in both plant species under a variety of conditions. The persistence of foliar-applied pymetrozine i s comparable on tomato and on sugar beet plants. Following drench appl ication, efficacy correlated with plant age and leaf development stage , but not with soil type. In conclusion, the variations in pymetrozine efficacy observed on tomato, sugar beet and pea against Myzus persica e (Sulzer) and Aphis craccivora (Koch) may be attributed to difference s of pymetrozine distribution within leaf tissues and/or host plant sp ecific feeding behaviour of aphids.