Exploring Biological Control of Greenhouse Pests

RALEIGH, North Carolina – Nursery growers looking for a biological control of thrips in the greenhouse may find success by incorporating a ‘Black Pearl’ pepper banker plant system to recruit natural insect enemies of the pest.

Sarah Wong, a graduate student studying entomology at North Carolina State University, is studying how ‘Black Pearl’ pepper plants support populations of the minute pirate bug (Orius insidious) – an aggressive predator of thrips – and how effective the bugs are in controlling thrip damage. The study is being funded by a two-year $9,959 Southern Sustainable Agriculture Research and Education (SARE) Graduate Student Grant.

Sarah Wong picking peppers.

“In the greenhouse industry, thrips are one of the most economically damaging pests, feeding on at least 260 plant species, including leafy vegetables and flowers,” said Wong. “Nursery growers are starting to show interest in ‘Black Pearl’ pepper plants as banker plants because they can be encouraged to flower year-round, thereby providing pollen as a food source and attracting beneficial insects even when there is no prey present. But they are not really sure what the impact Orius pressure is having on thrips.”

Thrips are a damaging greenhouse pest.

Wong is hoping to provide nursery growers with some solid data on the cost and effectiveness of implementing and maintaining a biological control program compared to current Integrated Pest Management strategies, which generally involve some level of pesticide use.

Wong is working with Hoffman Nursery, one of the largest ornamental grass growers on the East Coast, for her research.  In her first year of study, Wong surveyed pest abundance in three different treatments: control (no pesticide, no beneficial, no banker plants); augmentation (no insecticide, release of Orius insidious, and no banker plants); and banker plant (no insecticide, release of Orius insidious, and banker plants).

Preliminary results revealed that in the augmentation and banker plant treatments there were lower thrip populations than in the control. However, Wong didn’t see a significant difference in thrip populations between the augmentation and banker plant treatments.

“We have a few theories as to why that is. One is that we feel that flowerbeds around the greenhouses were pulling populations of Orius insidious away from the banker plants. We also found lots of jumping spiders, which will eat minute pirate bugs like nobody’s business,” said Wong. “Lastly, we suspect that the pollen from the pepper plant flowers was providing a secondary food source enough to where it didn’t impact thrip populations.”

This summer, Wong plans to conduct a series of controlled caged trials to eliminate the issue of immigration and predation, as well as determine the ratio of thrips compared to the ratio of pepper plant flowers, and therefore determine how many minute pirate bugs a banker system can support and effectively manage the thrips.

“We are hoping to see a difference related to the issue of immigration and predation, but we really don’t know what we are going to find with the pollen experiment,” said Wong. “Whatever the end results, they will be good educational tools for growers, especially when it comes to using biological controls. So many growers don’t really know what that is and it will be good to provide them with something that will allow them to become more familiar with the management system.”

Read more about the study, “The Black Pearl Pepper Banker Plant for Biological Control of Thrips in Commercial Greenhouses,” on the national SARE database and search for Project Number GS10-089.

Graduate Student Grants Program, one of Southern SARE’s seven grant opportunities, is targeted to Masters and PhD students leading sustainable agriculture efforts throughout the Southern region.

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Published by the Southern Region of the Sustainable Agriculture Research and Education (SARE) program. Funded by the USDA National Institute of Food and Agriculture (NIFA), Southern SARE operates under cooperative agreements with the University of Georgia, Fort Valley State University, and the Kerr Center for Sustainable Agriculture to offer competitive grants to advance sustainable agriculture in America's Southern region.