CHEMICAL CONTROL OF VINE WEEVIL LARVAE ON CONTAINER-GROWN HARDY ORNAMENTAL NURSERY STOCK 1986-1989

In a search for alternatives to the former standard aldrin compost inc orporation treatment for control of vine weevil (Otiorhynchus sulcatus ) larvae on container-grown hardy ornamental nursery stock, a series o f 87 tests of insecticides were done at four experimental centres of t he ADAS (Leeds, Reading, Wolverhampton and Wye) from 1986 to 1989. Ins ecticidally-treated plants and untreated controls were artificially in fested with vine weevil eggs at varying intervals before and after tre atment, and the survival of the pest was assessed. Aldrin treatment ga ve consistent and excellent preventive control of vine weevil larvae f or over 2 years. Of the candidate materials tested, a slow-release gra nular formulation of chlorpyrifos incorporated into compost at a dose rate of 100 g a.i. m(-3) of compost gave good control for up to 34 wk after treatment (the longest period evaluated) and a micro-encapsulate d slow release formulation of fonofos incorporated at a dose rate of 4 3.3 g a.i. m(-3) usually gave good control for up to two years (the lo ngest period evaluated). Surface applications of these two organophosp hates or of carbofuran granules, though sometimes effective, were unre liable as either preventive or remedial treatments even for short term control.