An Unusual Pest: Clover Mite
Several unusual samples came into the Diagnostic Lab this week. One notable is clover mite (Bryobia praetiosa) causing damage to New Guinea impatiens. Common around residential landscapes, it occasionally becomes a nuisance pest invading homes in spring. I sometimes see clover mites on weeds like clover and oxalis in and around greenhouses in spring but rarely on crop plants. In this case a population had built up on (what appears to be) hairy vetch (leguminous weed) growing around benches. Mites then moved onto New Guinea impatiens plants nearby where feeding on the upper surface was causing a kind of pale stippling. Damage was very localized along the perimeter near where the weeds were present, which were also showing symptoms of heavy damage. In this case removing the weeds by hand-pulling would be advisable with just spot-treating the crop where needed. A few products are labeled for clover mite specifically, including Floramite (or generic bifenazate) and various bifenthrin materials. Maintaining a grass- or weed-free 18 - 24" band around the structure perimeter can help discourage mites from moving into the range from outdoors.
Dan Gilrein
Entomologist, Cornell Cooperative Extension of Suffolk CountyDan 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.
