Control of spider mites in eggplants and thrips in field sweet peppers using guardian plants and predators

Project Overview

Project Type: Partnership
Funds awarded in 2011: $13,275.00
Projected End Date: 12/31/2012
Region: Northeast
State: New York
Project Leader:
Carol Glenister
IPM Laboratories, Inc.

Annual Reports

Information Products


  • Vegetables: eggplant, peppers


  • Crop Production: intercropping
  • Pest Management: biological control, integrated pest management, trap crops

    Proposal abstract:

    In 2010, Mark Zittel of Amos Zittel and Sons, Inc. experienced extremely high numbers of thrips on sweet pepper plants that they had transplanted from the greenhouse to a nearby field. Although they sprayed 5 times, they still experienced significant damage to the field. Beneficial insects and mites are extremely successful at controlling thrips in greenhouse peppers because the pepper flowers support continuous reproduction of the predators Orius and Neoseiulus cucumeris. We propose adding marigold Guardian Plants to the peppers to pull thrips from the pepper plants and support Orius reproduction until the peppers begin to flower. In another area of the farm, imidicloprid pesticide used in June to control Colorado Potato Beetle on eggplant devastates the spider mite predator population in June. With no natural suppression, the spider mites flare up and start bronzing the fields, requiring 2 summer sprays. Beans are particularly good trap plants for spider mites and can be planted in the middles of tractor lanes that are free of the pesticide. Predator mites released onto those beans in a July 2010 preliminary trial spread at least four rows into the eggplants and suppressed the spider mites to a level similar to miticides in the rest of the field. We would like to document the effect of the beans as Guardian Plants in eggplants. Our project is the first outdoor documentation of Guardian Plants that pull pests out of crops and support natural enemy reproduction in field vegetables.

    Project objectives from proposal:

    This project is the first outdoor documentation of Guardian Plants that pull pests out of crops and support natural enemy reproduction in field vegetables. With weekly scouting, we will track the establishment and production of our natural enemies, the single most important indicator of the predator’s continued ability to perform in the field. Furthermore, the in depth scouting will give us an indication of how far the predators spread from the Guardian Plants so that we can have a better way to estimate how far apart to space the Guardian Plants in the field.

    Mark Zittel and the Zittel farm staff will care for the pepper plants and eggplants as part of their normal production in spring 2011. In addition, they will grow and transplant the marigolds into the experimental field and plant the bush beans in June in the middle of the tractor lanes in the eggplant field. Mark will release the Orius into the greenhouse when the marigold flowers are abundant and, if needed, the pepper field in May and June, and predatory mite, N. fallacis into the eggplant field when the spider mites are evident on the beans. He will also share his experiences with other growers as opportunities arise.

    In all cases, Zittel’s reserves the right to treat with pesticides if the mites or other pests are at economically damaging levels. However, they will strive to choose pesticides that will minimize harm to the predators.

    Robert Hadad will manage a scout from mid April through mid September. The scout will make pest and predator counts on the Guardian Plants and crop in treated and control areas, differentiating between Orius nymphs and adults. IPM Laboratories will train and guide the scout and perform the data analysis. The predator and prey numbers will be charted on graphs of weekly plant observations in terms of number of pests and predators on the crop and guardian plants and controls.

    In the eggplants/snapbean Guardian Plant System for spider mite control, weekly scouting will be performed to answer the following questions: How far will the predators spread from the bean release site? If there are no beans, will the predators establish on the eggplant rows onto which they were released? If so, how far do they spread from the release rows? We will assess spider mite and predator levels on the bean rows, eggplants in rows adjacent to the release sites, eggplants 2 rows and 4 rows away from the release sites, eggplants that had predators released onto them directly and eggplants in treatments that received no predators.

    For the pepper/marigold Guardian Plant System, the marigolds will be transplanted to the field in two spacings (singly and groups of 25) amongst the pepper plants. If the Orius numbers are low, a third release of Orius adults will be made into the pepper field directly onto the marigold plants.

    Weekly scouting on the peppers and marigolds will start in the greenhouse in mid April recording whole plant inspections for thrips and aphids and yellow sticky card counts for thrips, whiteflies, fungus gnats and shoreflies. Scouting in the pepper field will concentrate on counts of number of flowers, thrips, Orius nymphs and Orius adults from beat samples of 30 pepper plants and 30 marigolds per treatment. A second pepper field under conventional pesticide management will be scouted weekly in the same manner as the control field. The conventional field will receive the same number of Orius as the treated field.

    If we are successful in the pepper/marigold Guardian Plant System Evidence of Orius establishment and reproduction will be demonstrated by the presence of their nymphs in the marigold flowers.
    The marigolds will draw thrips away from the pepper plants, resulting in few thrips on the peppers and obvious thrips on the marigolds. The Orius will keep the thrips numbers from exploding on the marigolds. As the peppers begin to flower, the Orius will transfer over to the pepper plants and reproduce on them as well. Thrips numbers will subside with the expanding natural enemy population. This scenario will be charted on graphs of weekly plant observations in terms of number of thrips and Orius per flower on the marigolds and on the peppers.

    If we are successful in the eggplant/bean Guardian Plant System Evidence of predator mite establishment and reproduction will be demonstrated by the detection of predators on the beans. The beans will show spider mites before they appear on the eggplants. The predator mites will spread from the beans to the eggplants. Spider mite numbers will be suppressed in the presence of the predatory mites.

    The cooperators will prepare a powerpoint presentation of the results and a two sided full color flier explaining the Guardian Plant concept and the predators (400 copies) to distribute at meetings and on the web. The cooperators will offer to share the results at grower meetings, including the NY Fruit and Vegetable Conference in Syracuse in January and the Mid-Atlantic Fruit and Vegetable Conference in Hershey in February.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.