Fungi, Predatory Mites and Guardian Plants for Thrips IPM in Organic Greenhouse Ornamentals

This project addressed a serious pest of organic greenhouse production nationally. In Vermont, thrips are the most common reason for organic growers suspending organic practices in their greenhouse crops, fearing the loss of their entire crop to this persistent virus-transmitting pest. Even growers who rely on chemical control find the standard insecticides ineffective due to resistant pest populations. Biological control approaches for thrips will directly benefit organic producers, but will also meet the need of “traditional” growers who seek to produce plants more ecologically. The innovative IPM strategy we tested could offer economic benefits to growers by reducing thrips damage, increasing plant quality and minimizing production costs by providing a sustained source of biological controls in the crop. It builds on our research over the past 2 years supported by the USDA and national grower associations to assess marigolds as indicator plants. We found marigolds were highly attractive to WFT and were an effective monitoring tool, but they also became a reservoir for the pest. We project the marigold guardian plant system will both supply sustained WFT biological control and serve as an effective early detection tool for greenhouse pests. Because we are conducting this work in a commercial bedding plant crop, our results will directly apply to the “real world” and will be readily adoptable by other growers.