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Weed ‘Em or Weep

Thu, Feb 24th, 2022, created by Dan Gilrein

To re-start our twospotted spider mite colony in early February we went on an expedition around the property to locate overwintering mites. Between bouts of snow and despite the cold (to around 15°F/-9.5°C) we sighted our quarry on some winter annuals. We also found some interesting aphids – some winged (!) and a few parasitized– and several species of thrips, including western flower thrips.  Still unsated, back indoors under the benches we found some greenhouse whiteflies, twospotted spider mites, and western flower thrips thriving on some common groundsel (another winter annual) and greenhouse whiteflies reproducing on young dandelion plants.  I recall reading how some of these winter annuals (like chickweed) are ‘bridge’ hosts for overwintering tospovirus vectored by western flower, tobacco, and some other thrips, creating problems for southern tomato growers. Winter annuals were abundant in the greenhouse perimeter and I wonder if we could experience something analogous here.

We may not be able to completely exclude pests coming from outdoors especially in warmer climates or times of year, but our observations might be a reminder to address these ‘starter’ pest populations early and at the source before they get going in the crop.

About the Author:

Dan Gilrein

Entomologist, Cornell Cooperative Extension of Suffolk County

Dan Gilrein is the Extension Entomologist with Cornell Cooperative Extension of Suffolk County at the Long Island Horticultural Research and Extension Center, Riverhead, NY since 1995 and previously served there as IPM Specialist with Cornell from 1987. In his current position he conducts applied research on control of arthropod pests in food crops and on ornamental plants, provides diagnostic services to the horticultural industries, and conducts educational programs and presentations for industry, government officials, civic groups and the public on pests and pest management.

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