Temperature-dependent development of parasitoid wasp, Telenomus busseolae on Sesamia cretica

The sugarcane stem borers, Sesamia cretica Lederer and S. nonagrioides Lefever are the most important pests of sugarcane in Iran causing heavy losses in cane and considerable reduction in sugar yield. The egg parasitoid wasp, Telenomus busseolae Gahan is the most remarkable natural enemy of Sesamia spp. in Khuzestan province, Iran that plays an important role in regulating the populations of sugarcane stem borers. Temperature is an effective abiotic factor that influences the development of natural enemies. The present study aimed to investigate the temperature-dependent development of T. busseolae on S. cretica.

The development rates and thermal constant of the immature stages of T. busseolae on S. cretica eggs were studied at seven constant temperatures (15, 18, 20, 25, 30, 35, and 37ºC), a photoperiod of 16L:8L, and 65%±5% RH. Fresh egg masses of S. cretica were exposed to the newly mated female of T. busseolae for 6 h. Afterwards, the parasitized eggs were kept at different temperatures. The parasitized eggs were checked daily until adult emergence. Development rate was modeled as a function of temperature using two mathematical models, including common and Ikemoto and Takai linear models. The linear models were analyzed using the SAS software.

The results of regression analysis showed that the immature developmental period of T. busseolae decreased with elevating temperature from 18ºC to 35ºC. In 15ºC and 37ºC, no development rate was found for T. busseolae. Immature development time declined from 45 to 11 days and 46 to 12 days in male and female parasitoids, respectively. The percent of adult emergence was not affected by temperature. However, two linear models provided a satisfactory relationship between immature development rate and temperature. Based on statistical criteria, Ikemoto and Takai linear model estimated thermal constant and temperature threshold more precisely. For male and female parasitoids, the thermal constant was 250 and 255 degree-days and the low-temperature threshold was 12.44ºC and 12.5ºC on S. cretica eggs, respectively.

In the current study, the thermal requirement of T. busseolae on S, cretica was estimated for the first one. Information regarding the thermal requirement of T. busseolae can be useful for the rearing and application of this parasitoid in the biological control of sugarcane stem borers. This finding could be used to predict the number of T. busseolae generations and the best time for parasitoid release in sugarcane fields.