[Development and reproduction of Sipha flava (Forbes) (Hemiptera: Aphididae) at different temperatures]

The aphid Sipha flava (Forbes) is a pest on elephant grass, but little is known about its biology. The objective of this work was to evaluate the temperature effects on the development, survival and reproduction of S. flava fed on Pennisetum purpureum. Twelve-hour-old nymphs were individualized on sections of elephant grass blades and maintained at 12, 16, 20, 24, 28 and 32 degrees C+/-1 degrees C, UR 70+/-10% and 12 h photophase. A total of 150 nymphs were used per treatment divided in 30 replicates, using a totally random design. The lower threshold temperatures (LTT) for first, second, third and fourth instars were 0.83, 1.05, 3.01 and 4.98 degrees C, respectively, indicating a change in thermal requirements as the development progress. The LTT for the whole nymphal stage was 2.08 degrees C, pointing to the tolerance of this species to low temperatures. A significant reduction in survival was observed at high temperatures (28 and 32 degrees C). Although the reproductive periods were longer and insects lived longer at 12 degrees C as compared with those at higher temperatures, the total fecundity was substantially reduced. The overall life cycle duration was almost twice as long at 12 degrees C than at 24 degrees C. The greatest daily production of nymphs and greatest number of nymphs produced overall occurred at 24 degrees C. The temperatures of 20 degrees C and 24 degrees C were more suitable to S. flava development and reproduction.