Thermal requirements and estimate of the annual number of generations of Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) on strawberry crop

Frankliniella occidentalis (Pergande) is one of the major strawberry pests in southern Brazil. The insect causes russeting and wither in flowers and fruits reducing commercial value. In this work, the thermal requirements of the eggs, larvae and pupae of F. occidentalis were estimated. Thrips development was studied in folioles of strawberry plants at six constant temperatures (16, 19, 22, 25, 28 and 31 deg C) in controlled conditions (70 +- 10% R.H. and 12:12 L:D). The number of annual generations of F. occidentalis was estimated for six strawberry production regions of Rio Grande do Sul State based on its thermal requirements. Developmental time of each F. occidentalis stages was proportional to the temperature increase. The best development rate was obtained when insects were reared at 25 deg C and 28 deg C. The lower threshold and the thermal requirements for the egg to adult stage were 9.9 deg C and 211.9 degree-days, respectively. Considering the thermal requirements of F. occidentalis, 10.7, 12.6, 13.1, 13.6, 16.5 and 17.9 generations/year were estimated, respectively, for Vacaria, Caxias do Sul, Farroupilha, Pelotas, Porto Alegre and Taquari producing regions located in Rio Grande do Sul State, Brazil. (author)