The development of a comprehensive IPM program to manage western flower thrips and Tospoviruses in a bedding plant nursery in California
Parrella M, Costamagna T
Department of Entomology, University of California, Davis, CA. USA.
Correspondence: mpparrella@ucdavis.edu
Thrips and tospovirus [most notably the western flower thrips (Frankliniella occidentalis) and Impatiens necrotic spot virus, are perennial problems for most commercial floriculture operations in California. With large thrips¨ populations developing in areas adjacent to greenhouse/nurseries, migration of viruliferous thrips into sensitive cropping areas occurs every year. Unless a comprehensive management plan is in place, growers are often forced into a reactionary mode, where the only recourse is the use of regular pesticide sprays. Depending on the degree of migration, possible resistance in the target populations and the selection and type of application of pesticides, pesticides alone are often not be enough to provide satisfactory thrips and virus control. This past year we have worked with one large nursery where they have sprayed as much as 35 times per year for control of thrips (virus) and other pests, with little effect. We have dramatically reduced the number of sprays used in this greenhouse/nursery and have achieved much better control of thrips and virus. We hope that the steps taken in this operation could serve as a model for other nurseries to follow. Cultural/physical tactics adopted by this greenhouse/nursery included adding concrete floors to some of the greenhouses, sanitizing greenhouses between crops, using thrips-proof screening, treating plants prior to moving them from the field to the greenhouse, adding baffles and/or screened foyers at the entrance to the greenhouses, and planning crop location and movement to minimize contamination with thrips. A monitoring program was put into place for thrips and tospovirus, predatory mites were included as an overall control tactic, and pesticide selection was based on bioassays conducted with thrips collected from this nursery. Many of these tactics are not minor and required considerable expense by the nursery. The overall result has been better pest control with fewer pesticides.
