Chili Thrips Resistance Management - Special
Dr. Lance Osborne, University of Florida, $25,000, 1 year project
Executive Summary
Thrips cause serious economic losses in many agricultural systems each year including vegetables and ornamentals. Although there are a number of thrips species attacking greenhouse floriculture crops, western flower thrips (Frankliniella occidentalis) is the predominate species causing economic losses. Scirtothrips dorsalis is a new invasive species causing severe economic damage in floriculture and nursery crops. This new invasive species has resulted in a significant challenge to ornamental production systems and threatens established IPM programs for traditional pests.
Even though western flower thrips have been a pest for over 15 years in most of the United States, floriculture producers are still relying on pesticides as their primary means of management. There are currently only two insecticides, Conserve (Spinosad, Dow AgroSciences LLC) and Pylon (Chlorfenapyr, OHP, Inc.), that have proven to give consistent levels of western flower thrips control. Unfortunately, growers often apply these products as frequently as once a week. This frequent application of two pesticides increases the potential for developing pesticide resistant or tolerant strains. Pesticide tolerance has recently been documented in floriculture crops (Loughner et al, 2005, Ludwig, personal observation). When battling thrips, growers must also contend with phytotoxicity, labor costs associated with frequent pesticide applications, reentry periods into treated areas, arrival of new pests, and the occasional loss of an effective pesticide due to health hazards. Biological control of thrips has been proposed as a solution to these problems (Heinz et al. 2004), but has not been widely adopted by floriculture producers. Biological control is a viable alternative to chemicals in several perennial crops, strawberries, vegetable and ornamental crops grown in greenhouses.
Scirtothrips dorsalis was first detected in Highlands County, Florida, in 1991. Sampling indicated S. dorsalis had not established a population. Subsequently, S. dorsalis was detected on roses from Palm Beach County, Florida in 2005. As of August 23, 2007, S. dorsalis have been detected in Florida from Duval County (on the northern border with Georgia) to Monroe County (the Florida Keys) and in South Texas retail garden centers. In the Western Hemisphere, S. dorsalis have also been detected in Hawaii and the following locations in the Caribbean: Barbados, Jamaica, St. Lucia, St. Vincent, Tobago and Trinidad. Scirtothrips dorsalis is a polyphagous species and has been documented to attack more than 100 recorded hosts from about 40 different families. As this pest expands its geographical range additional plants are added to its host range. Among ornamentals, host plants include roses, chrysanthemums, Gerber daisy, geraniums, dahlia, viburnum, zinnia, Mexican heather, petunia, poinsettia, coleus and verbena. Some trees and shrubs also shelter these pests, including crape myrtles, camelia, Japanese holly, maple, ligustrum, eunomymus, rubber trees, and pittosporum. The life cycle for S. dorsalis is similar to that of western flower thrips. Female S. dorsalis insert their eggs inside plant tissue. The eggs hatch in 6-8 days. They pass through two larval stages (1st and 2nd instars) that last for 6-7 days. During this time they actively feed on the host plant. They then pass through a prepupal (-24 h) and pupal stages (2-3 days) during which time they do not feed. They can complete their life cycle in 14-20 days. The thrips female oviposit 60 to 200 eggs in her lifetime.
For further information, please contact Lance Osborn at lsosborn@ufl.edu
