Effect of Temperature on Fecundity and Longevity of Adults of Sunn-pest (Eurygaster integriceps)

Temperature is one of the most important factors affecting biological characteristics such as longevity and fecundity of insects. Knowledge on such effects assists us to understand causes of population fluctuations. Effect of temperature was studied on fecundity and adult longevity of sunn-pest Eurygaster integriceps Put. One week old Mahdavi wheat cultivar seedlings were used for this purpose. Four temperatures 30, 27, 25, and 22 ± 1 ºC were included and experiment was repeated in 1998 (excluding 25 and 22ºC) and 1999 on the basis of a completely randomized design. Effect of temperature on fecundity and post-oviposition period was non-significant while it was significant on longevity, pre-oviposition and oviposition periods. Population fecundity was 64% more and pre-oviposition period 30% shorter at same temperatures in 1998 than 1999. This may imply that physiological status of the bugs has been more favorable in 1998. Pre-oviposisional period showed a significant increase with corresponding decrease in temperature. Thermal threshold and thermal constant for development of pre-oviposition period were determined as 19.48ºC and 122.78 Degree-Days respectively. Ovipositional duration even though without a particular trend, was affected by temperature. It was totally longer and then height of reproduction curve was shorter in the two lower temperatures compared to other ones. Referring to simultaneous increase in pre-oviposition and ovipositional periods, life span was significantly broader in lower temperatures. Two males were encountered in rearing media that were infected by a cephalobiid parasitic nematode. This is the first record of a Cephalobiidae on sunn-pest.