Effects of temperature on survival, oviposition, and development rate of "greenhouse" and "lupin" strains of western flower thrips, Frankliniella occidentalis

Two strains of western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), are found in New Zealand. One strain was recorded in 1934 mainly from outdoor Lupinus arboreus Sims (lupin strain, a non-pest); the other strain was first recorded in 1992 and is found mostly on greenhouse crops (greenhouse strain, a pest). To test whether this differential pest status may be explained by different temperature requirements, a comparative life-history study was carried out assessing the effects of temperature on life-history traits and thermal requirements for development. Thrips strains were verified using sequence alignment of the COI gene. Thrips from each strain were fed sucrose solution and pollen, and they were reared at 8, 10, 12, 17, 22, and 27 (+/- 2) degrees C, respectively (>80% r.h., L16:D8 photoperiod). Longevity decreased with increasing temperature for both strains; however, the greenhouse strain had a significantly longer lifespan at all temperatures. Overall, the greenhouse strain laid more eggs than the lupin strain at all temperatures, with the highest mean number laid at 22 degrees C for the lupin strain (36.3 total eggs/female) and at 17 degrees C for the greenhouse strain (63.2 total eggs/female). No significant difference between the two strains was found in regards to the effect of temperature on development rate, T-min (minimum temperature required for development), and D-o (degree days). We estimated that 227 degree-days, above a threshold temperature of 7.7 degrees C, were required to complete development of the greenhouse strain. No life-history data of either strain were obtained for 8 degrees C as eggs did not hatch or development had not completed. The lupin strain required 261 days above 5.7 degrees C for complete development. The results of the study did not support the hypothesis that the lupin strain's outdoor non-pest status was due to different temperature requirements compared with those of the greenhouse strain.