Effect of Temperature and Host on the Development, Sex Ratio, Emergence Rate and Body Size of Trichogramma dendrolimi Matsumura (Hymenoptera: Trichogrammatidae), an Egg Parasitoid of the Tea Tortrix

Abstract

Abstract:The development, sex ratio, emergence rate, and body size of the egg parasitoid Trichogramma dendrolimi Matsumura (Hymenoptera: Trichogrammatidae), reared on the eggs of Adoxophyes honmai and Homona magnanima, were investigated in the laboratory at five constant temperatures (16, 20, 24, 28, and 32°C). Although the developmental rate of T. dendrolimi reared on both hosts increased significantly with increasing temperature, the developmental rate of T. dendrolimi reared on the eggs of H. magnanima increased significantly with increasing temperature more rapidly than those reared on the eggs of A. honmai. The developmental zero and total effective temperatures for females and males reared on the eggs of A. honmai were 11.7°C and 120.5 degree-days and 11.5°C and 119.0 degree-days, respectively. The developmental zero and total effective temperatures for females and males reared on the eggs of H. magnanima were 11.7°C and 114.9 degree-days and 11.7°C and 116.3 degree-days, respectively. The sex ratios (female/total) of adults emerging from the eggs of A. honmai and H. magnanima were 0.76-0.89 and 0.71-0.77, respectively. The sex ratio of adults emerging from the eggs of A. honmai was significantly higher than that of adults emerging from the eggs of H. magnanima. The percentage adult emergence rates of T. dendrolimi [{numbers of emerged adults/(numbers of emerged adultsϩnumbers of dead individuals inside eggshells)}ϫ100] reared on the eggs of A. honmai and H. magnanima were 23.5-73.4% and 41.8-85.0%, respectively. The adult emergence rates of T. dendrolimi reared on both hosts decreased significantly at an accelerating rate with increasing temperature. The head widths of female and male adults emerging from the eggs of A. honmai were 0.172-0.186 mm and 0.168-0.188 mm, respectively, whereas those of female and male adults emerging from the eggs of H. magnanima were 0.202-0.216 mm and 0.195-0.212 mm, respectively. The head widths of T. dendrolimi reared on the eggs of A. honmai increased significantly with increasing temperature. In contrast, the head widths of T. dendrolimi reared on the eggs of H. magnanima decreased significantly at an accelerating rate with increasing temperature.