Effect of temperature on the development and viability of Gryon gallardoi (Brethes) (Hymenoptera: Scelionidae) parasitizing Spartocera dentiventris (Berg) (Hemiptera: Coreidae) eggs

Abstract

The development and viability of Gryon gallardoi (Brethes) (Hym.: Scelionidae) in Spartocera dentiventris (Berg) (Hem.: Coreidae) eggs were studied under four temperatures: 15, 20, 25, and 30 ± 1ºC, with a 12-h photophase. No parasitoid developed at 15ºC. Otherwise, viability reached 98.8% without varying significantly over the temperature range tested. The duration of development for males and females was inversely proportional to the temperature increase, varying respectively from 46.2 ± 0.13 and 47.1 ± 0.11 days (20ºC) to 13.3 ± 0.07 and 13.4 ± 0.06 days (30ºC). Males developed faster than females. The values estimated for the lowest thermic thresholds of development and the thermic constants were 15.5ºC and 185.19 DD for males and 15.6ºC and 192.31 DD for females, respectively. Given the average weather conditions in Porto Alegre, RS (30º01'S and 51º13'W), Brazil, G. gallardoi could annually produce 8.54 and 8.07 generations of males and females, respectively. The low rates of parasitism observed in the field during the first generation of its host may be due to the small number of G. gallardoi generations in this period.