Optimal Management of Lepidopteran Pests of Grapes
The primary objectives of this research project are: 1) To evaluate and refine monitoring programs for western grapeleaf skeletonizer (WGLS) and omnivorous leafroller (OLR) in grapes, and 2) To determine spatial and temporal patterns of WGLS and OLR distribution in order to develop a non-preventive, true IPM program for dealing with these two serious vineyard pests. During 1992 (first year of project), several significant results were produced. Sex pheromone bucket traps with insecticide strips caught more WGLS moths at peak flight than did traps with ehtylene glycol. OLR bucket traps with insecticide strips were somewhat more efficient than sticky bottom pheromone traps. With respect to monitoring OLR larvae, the UC recommended bunch count technique (developed mostly on Thompson seedless), appeared to have questionable applicability for detecting OLR in tight-clustered grape cultivars. Thus, early season OLR infestations, readily evident before berry sizing in such cultivars, later became “invisible” as the clusters developed. For all the commercial vineyard blocks which were sampled in 1992, the grower did not feel it was necessary to use chemical control at any time of the season, based on the pest monitoring data which we compiled. Thus, although there was no opportunity for comparing relative efficacies of alternative insecticide materials during 1992, we were certainly able to demonstrate that preventive treatment for these lepidopteran pests of grapes is by no means an essential activity in San Joaquin Valley vineyards.