Spring activities of Conotrachelus nenuphar
Spring activities on apple trees of adult plum curculios, Conotrachelus nenuphar (EPPO A1 pest), were the objects of an investigation carried out in Quebec, Canada.
Radioactively labeled plum curculios were released in field cages containing several dwarf apple trees and then monitored throughout the spring season. From full bloom to 9 d after fruit set the weevils were active on the trees mainly during the night. From full bloom to petal fall they spent most of their days on the ground beneath the apple trees but gradually invaded the trees until, by fruit set, most were in the trees.
By fruit set the beetles were most active during the late afternoon and night.
Basing on this knowledge the authors suggest that pesticides are best applied in the late evening during the spring season.
Sources
Racette, G.; Chouinard, G.; Hill, S.B.; Vincent, C. (1991) Activity of adult plum curculio (Coleoptera: Curculionidae) on apple trees in spring.
Journal of Economic Entomology 84, 1827-1832.