Monitoring and management of thrips populations in vegetables, row crops, and greenhouse crops in Virginia
Andrews, Heather Elizabeth
MetadataShow full item record
Thrips are pests in a variety of crops and are responsible for millions of dollars in damage worldwide. In Virginia there are a few key thrips species that cause a large portion of damage to both vegetable and floricultural crops. Three prominent pests include Frankliniella tritici (Fitch), Frankliniella fusca (Hinds), and Frankliniella occidentalis (Pergande). Significant yield losses in row crops such as cotton, peanuts and vegetables have been attributed to feeding and oviposition of these insects in high densities. In addition, both F. fusca and F. occidentalis can transmit plant pathogenic tospoviruses, such as tomato spotted wilt virus (TSWV), in certain susceptible crops. While all of these thrips species are difficult to detect due to their cryptic lifestyles, F. occidentalis is a particularly challenging pest to manage due to its resistance to many insecticides commonly used for thrips treatment. Early spring weeds were sampled for the presence of F. occidentalis in 2008 and 2009 in eastern Virginia. Weed samples consisted of mustard, henbit and wild radish and were collected from several different sites on the Eastern Shore of Virginia. During the summer of 2008, 2009 and 2010 various agroecosystems were sampled for the relative incidence of F. occidentalis. Overall, thrips numbers were very low in weed samples. F. occidentalis was detected in early spring weed samples in 2009 at a few of the sites sampled. In nearly every habitat, the species composition was dominated by F. fusca and F. tritici, with F. occidentalis occurring in very low numbers. Two different lures were evaluated in their ability to attract Frankliniella spp. thrips. The lures included Chemtica P-178 floral kairomone (AgBio Inc., Westminster, CO), a floral iii kairomone lure composed of a proprietary floral compound mixture, and ThriplineAMS (Syngenta Bioline Ltd., Oxnard, CA) pheromone lure, containing the aggregation pheromone of F. occidentalis. In spring 2009 and 2010 lure experiments were conducted in several different agroecosystems including: a tomato and potato field in Painter, VA, a cotton and peanut field in Suffolk, VA, and grass fields near a greenhouse in Virginia Beach, VA, and a high tunnel in Chesapeake, VA, as well as within these structures. Baited and non-baited sticky cards were arranged in a completely randomized design, with a pan trap located in the center of each plot. Traps were collected approximately twice weekly. F. fusca numbers were low and catches on sticky cards were not significantly affected by either lure. Sticky cards baited with the kairomone caught more flower thrips than traps baited with the pheromone, or the non-baited traps, especially when thrips numbers were high. Several biologically derived insecticides including: essential oils, spinetoram, spinosad, pyrethrins, and azadirachtin, were evaluated in their efficacy against thrips in several different crops. Randomized complete block design experiments were carried out in: tomatoes, snap beans, collards, soybeans, cotton and peanuts grown in several locations in southeastern Virginia in 2009 and 2010. Both spinetoram and spinosad reduced thrips numbers the most effectively compared with the untreated control. Peanut and cotton treated with spinosad, and treatments containing spinetoram suffered less thrips injury compared with the control, and yield was higher in cotton plots treated with spinetoram.
- Masters Theses