Development of Frankliniella species (Thysanoptera : Thripidae) in relation to microclimatic temperatures in vetch

Continuous generations of Frankliniella occidentalis (Pergande) and F. fusc a (Hinds) develop through the winter and spring in northern Florida on plan t hosts such as hairy vetch, Vicia villosa Roth. Previously reported resear ch compared development under field conditions of these thrips to predictio ns of temperature-dependent developmental models obtained in laboratory exp eriments and concluded that accumulated degree-days of ambient temperatures recorded at a nearby national weather station underestimated development o f populations developing under field conditions. Thus, the objective of thi s study was to compare ambient temperatures to microclimate temperatures in V. villosa plots and its effect on thrips development. An electronic data logger was used in this experiment to continuously record over 63 d ambient , upper plant canopy, middle plant height, lower plant height, and soil tem peratures in plots of V. villosa. The microclimatic temperatures and their degree-day accumulations, based on daily maximum and minimum records, were significantly greater (P = 0.05) than the ambient temperature and degree-da y accumulations obtained from a nearby National Oceanic and Atmospheric Adm inistration (NOAA) weather station. There were no significant differences i n mean temperature and degree-day accumulations within the upper, middle an d lower portions of V. villosa plants. Based on degree-day accumulations in the upper plant canopy, 3.1 generations were predicted for F. occidentalis and 2.4 generations for F. fusca during the study. However, using the NOAA degree-day accumulations, only 2.5 and 1.9 generations were predicted, res pectively. During this study, an accumulated discrepancy of 3/4 of a genera tion was calculated for F occidentalis and more than half of a generation f or F. fusca between the NOAA weather data and the microclimate data. Thus, ambient temperatures obtained from the NOAA weather station would underesti mate development, as was observed and reported previously. The results demo nstrated the importance of using microclimatic measurements, rather than am bient records, for best estimating developmental potential of thrips.