Flower thrips, oviposition and dispersion behavior in early-season blueberries
Ar¨¦valo HA, Liburd OE
Entomology and Nematology Department, University of Florida, Gainesville, FL 32611 USA.
Correspondence: aleareva@ufl.edu
United States is the largest producer of blueberries with an approximate value of 137,000 tons/year. This represents 65% of the total production worldwide. Early-season blueberries produced only in Florida and southern Georgia between the months of April and May have prices that can be three to five times higher than regular-season blueberries in northern US states. Flower-thrips from the genus Frankliniella are considered as key pests for early-season blueberries in the southeastern United States. Based on observations conducted between 2003 and 2005 during the blueberry flowering season, we determined that the predominant flower-thrips species of blueberries in Florida is F. bispinosa (Morgan), and in southeastern Georgia is F. tritici (Fitch). Other species present include F. occidentalis (Pergande), F. fusca (Hinds), Thrips hawaiiensis (Morgan), and T. pini Uzel. A series of observations in oviposition behavior and populations dynamics were made in Southern highbush (Vaccinium corymbosum x V. darrowi) and Rabbiteye blueberry (V. ashei), the two main species grown in Florida and Southern Georgia. The main objective of this work was to understand the oviposition preferences, movement and distribution of flower-thrips in early-season blueberries, with the ultimate goal of establishing an IPM program for controlling thrips. The results of our observations show a significantly higher number of thrips emerging from flower petals than from ovaries, styles or fruits (F = 19.16; df = 3, 158; P < 0.0001) of flowers collected in the field. This indicates a preference to oviposit on the petals than in any other tissues of the blueberry flower. There were no significant differences in thrips emergence between the two blueberry species evaluated, Rabbiteye (3.11 ˇŔ 1.2) and Southern Highbush (4.0 ˇŔ 1.5) (F = 0.01, df = 1,38; P = 0.93). At the beginning of the season when the flowers begin to open, thrips infestation is very sporadic and populations are relatively low. Flower-thrips clusters or ˇ°hot-spotsˇ± are defined 7 days after flowers begin to open. Thrips gradually increase in area and population for approximately 2 weeks. Thrips populations in these ˇ°hot spotsˇ± increase exponentially for approximately 14 days, until 90% of the flowers are open, then it declines until the thrips virtually disappear at petal fall. At this time only fruits are standing in the field illustrating a correlation with the phenology of the flowers. Based on this time-line and observations conducted in the laboratory, thrips may have at least one generation on blueberry flowers, affecting fruit quality by leaving scars from feeding, and injuring reproductive tissues by ovipositing, and emerging from the ovary. Thrips also affect and quantity of blueberries by dehydrating flowers that have been severely attacked.
