Temperature-dependent development of the predator, Scolothrips sexmaculatus (Pergande) (Thysanoptera:Thripidae)

Abstract

The temperature is an important factor that affects the efficacy of biological control agents. Effect of the temperature on life table, parameters of Scolothrips sexmaculatus (Pergande) (Thysanoptera: Thripidae), the predator of the two-spotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae) was studied under laboratory conditions at three constant temperatures (20, 25 and 30°C). The durations of development of egg, 1st and 2nd larval instars, pupa and adult at the three temperatures were measured. Total developmental period from egg to adult’s emergence was estimated by 23.2, 13.3 and 10.8 days, respectively. The developmental period decreased significantly with increasing the temperature from 20 to 30°C. Survival rate was highest at temperature (30°C) in comparison with the other temperatures. Egg stage of S. sexmaculatus showed highest mortality levels at all temperatures. Generation period, as well as the ovipositional period decreased significantly ranged from 25.1 to 11.54 and 52.8 to 41.2 days between the two temperature extremes, respectively. Maximum total fecundity (229.3 eggs/ female) and the minimum (94.1 eggs/female) were recorded at 30 and 20°C, respectively. Mean number of fertile eggs/ female/ day was highest at 30◦C (4.9 eggs) and lowest (2.7 eggs) at 20◦C. Thermal requirements for developmental thresholds and thermal constant of S. sexmaculatus were estimated as 10.8°C and 200 degree-days (DD), using the common linear model. 30°C was the optimum temperature for development. The results showed that the population of S. sexmaculatus was able to develop at a broad range of temperatures therefore it is well adapted to the temperatures of the Mediterranean region.