Western Flower Thrips
Thursday, 23 June 2005 10:39
Thrips populations remain high due to the warmer temperatures, especially for year-round growers. Look for thrips on their favorite crops including verbena, sunflowers, brugmansia, petunias, dahlias, asclepias, etc. Gently blow into the flowers to detect winged adults. Tap the foliage over a sheet of white paper to look for the adults and larvae. Often, during the summer months, action thresholds are higher than in the spring.
See photos of thrips damage to verbena flowers and foliage, 2
Thrips may be migrating from weeds (both inside and outside the greenhouse), from cull piles too close to the greenhouse, or from older stock plants or pet plants. Practice rigorous weed control and good sanitation to protect your younger crops from thrips.
Conserve is best used when you really need it--either to reduce significant thrips populations or late in the crop cycle when plants are in bloom. In a recent study in HortScience, resistance to spinosad (Conserve) was documented in a western flower thrips greenhouse population where conserve was applied on average five times a year since March 1999 with up to 8 applications in a single year! Be sure to rotate with insecticides with different modes of action and use alternative methods to control thrips.
See the New England Greenhouse Floriculture Guide for additional options on insecticides labeled for thrips.
One additional material not listed in the New England Guide is Tristar, whose label was recently expanded to include western flower thrips. See updated label at www.clearychemical.com
See Factsheet: Western Flower Thrips
Leanne
