Monday, December 10, 2007 - 8:05 AM

Steps toward determining an economic injury level (EIL) for thrips on southern highbush blueberries in Florida

Elena M. Rhodes, and Oscar E. Liburd, University of Florida, Entomology and Nematology, P.O. Box 110620, Building 970 Natural Area Drive, Gainesville, FL

During 2006, Florida produced 7 million lbs of fresh market blueberries at an average of $4.70 per lb. Despite this high price, blueberry production is threatened by high populations of thrips during flowering. Frankliniella bispinosa (Morgan) is the key pest affecting blueberries in Florida. The strategy used to manage these thrips is insecticide application, but an economic injury level (EIL) has not been determined. The objectives of our experiment were to 1) investigate varietal susceptibility, 2) quantify the relationship between thrips numbers and fruit injury, and 3) quantify the relationship between thrips per trap and thrips per flower. The experiment was conducted on two commercial farms in Heranado County using a completely randomized design. The four most popular varieties, Emerald, Jewel, Millennium, and Windsor, served as our treatments. Sticky traps and flower samples were used to monitor thrips populations. Twenty-five fruits were harvested from the four plants closest to the sticky traps and examined for thrips injury and marketability. There were significant differences in the number of thrips per trap and per flower among varieties on both farms. There were no significant differences in either injured or unmarketable fruit among varieties. This indicates that EILs must be developed separately for individual varieties. However, regression analysis showed only a weak relationship between thrips per flower and fruit injury in all four varieties. There is a moderately strong linear relationship between log10(thrips per trap) and 1/sqrt(thrips per flower). Once this regression is refined, growers can use sticky trap counts to estimate thrips numbers in flowers

Species 1: Thysanoptera Thripidae Frankliniella bispinosa (Florida flower thrips)
Species 2: Ericales Ericaceae Vaccinium corymbosum (southern highbush blueberries)