DEVELOPMENTAL RATE OF LIRIOMYZA-SATIVAE (DIPTERA, AGROMYZIDAE) ON LETTUCE AS A FUNCTION OF TEMPERATURE

Developmental rate of Liriomyza sativae Blanchard on lettuce, Lactuca sativa L., was determined under constant laboratory and fluctuating gr eenhouse temperatures. A degree-day model for predicting immature deve lopment under field conditions was developed from these data. Developm ental times for immature stages of L. sativae were inversely proportio nal to temperature. Total developmental times for the immature stages varied from 14.1 d at 30 degrees C to 50.8 d at 15 degrees C, with pup ae requiring more time for development than the combined egg and larva l stages. Lower developmental thresholds, estimated from linear regres sion equations between temperature and developmental rate, for the egg -larval, pupal, and total combined life stages were 8.9 degrees C, 9.8 degrees C and 9.4 degrees C, respectively. Based on the calculated th reshold temperatures for each life stage under fluctuating temperature conditions in the greenhouse, development from egg deposition to adul t eclosion was 271.6 +/- 3.9 degree-days, which differed from the pred icted estimate. In general, these data provide fundamental information describing the biological development of L. sativae that, when used i n association with other ecological data, may be useful for predicting growing conditions conducive to Liriomyza outbreaks on lettuce.