Biological Control of Two-spotted Spider Mite on Vegetables

View the project final report

Commodities

• Vegetables: tomatoes

Practices

• Education and Training: extension, on-farm/ranch research, participatory research
• Pest Management: biological control, biorational pesticides, chemical control, field monitoring/scouting, integrated pest management

Twospotted spider mite is a serious pest of solanaceous (tomato, eggplant) and cucurbit (cucumber, watermelon) crops throughout much of the southern U.S. A recent survey of NC vegetable growers rated it the number one arthropod pest of tomato. Control is achieved almost exclusively with expensive chemical acaricides, usually multiple applications per season, which has led to costly control measures and the development of acaricide-resistant populations. We have recently detected resident field populations of the predatory mite Phytoseiulus persimilis in tomatoes and cucurbits in Rowan County, NC, which is in the Piedmont Region of the state. This is a highly mobile specialist predator of TSSM that is commonly used worldwide for augmentative releases in greenhouse vegetable production, and in some instances in field strawberries. Resident field populations have not previously been detected in the southeastern U.S. Naturally occurring populations of P. persimilis in Rowan County have been observed to do an excellent job of controlling TSSM on tomatoes in late August and September, provided growers recognize them as beneficials and avoid spraying insecticides harmful to the predator. Unfortunately there is a considerable lag time between the buildup of TSSM and predators in tomato fields early in the season (July to mid-August), which is when mite populations and acaricide use are most intense. Field experiments completed in 2016 provide strong evidence that early season releases of tomato-adapted predatory mites in tomato plots accelerated P. persimilis buildup and maintained TSSM populations below economic injury levels for the entire season.

This project will determine the distribution of P. persimilis in different ecoregions of NC, develop a banker plant system (i.e. plants deployed in fields used to rear and release biological control agents) to accelerate the buildup of P. persimilis in tomato fields early in the season, and evaluate insecticide programs for their compatibility with biological control, efficacy in controlling key arthropod pests, and economic viability.

Finally a multifaceted outreach program will be developed to education extension personnel and growers on implementing P. persimilis-based biological control programs.

• To determine the distribution of resident populations of P. persimilis in different ecoregions of NC, and overwintering sites in regions where they successfully overwinter.
• To compare the efficacy of different commercial sources and release rates of P. persimilis in controlling TSSM on tomatoes.
• Determine the level of TSSM suppression in tomatoes using a within field tomato-based banker plant system and a periphery bean-based banker plant system for releasing P. persimilis into commercial tomato fields.
• Compare different insecticide-based management programs for compatibility with P. persimilis, efficacy in managing key insect pests, and net profitability of tomato production.