Effect of Carbohydrate Nutrition on Egg Load and Population Parameters of Four Trichogramma Species

Trichogramma parasitoids are the most widely used biocontrol agents and play a crucial role in the biological control of agricultural and forest pests. Many studies have shown that Trichogramma parasitoids feeding on carbohydrate rich diet can effectively improve their egg laying capacity and longevity. However, few studies have reported the impact of carbohydrate-rich diet on the biological parameters of different species of Trichogramma parasitoids. In this study, we compared the differences between the biological parameters of four Trichogramma species (T. dendrolimi, T. chilonis, T. leucaniae and T. ostriniae) before and after feeding on carbohydrate-rich diet. The results showed that all the biological parameters of Trichogramma species improved after feed on carbohydrate-rich diet. After eclosion, T. dendrolimi had the highest egg load (51.89 eggs) followed by T. chilonis (26.86 eggs), T. ostriniae (24.71 eggs), and T. leucaniae (12.44 eggs). Trichogramma dendrolimi showed an increased trend in egg load (66.7–86.21 eggs) after feeding on carbohydrate-rich diet, followed by T. chilonis (33.12–45.56 eggs), as compared to the other three species. Furthermore, T. leucaniae and T. ostriniae benefited much less from the ingestion of carbohydrate-rich diet, as only accelerated egg maturation in T. ostriniae was observed. Most of the egg loads consisted of matured eggs, so the trend of mature eggs was the same as that of the egg load. We also tested the population parameters of the Trichogramma species using the TWOSEX-MSChart. The results showed that the Trichogramma species fed with a honey diet had higher fecundities, i.e., T. dendrolimi (146.64), T. chilonis (173.53), T. leucaniae (83.69), and T. ostriniae (80.45), than when fed with water, i.e., 78.49, 40.15, 32.45 and 35.47, respectively. T. dendrolimi and T. chilonis had a higher intrinsic rate of increase r (0.4178 d−1, 0.3933 d−1), finite rate of increase λ (1.5186 d−1, 1.4818 d−1), and net reproductive rate R0 (130 offspring, 147.4 offspring), than T. leucaniae and T. ostriniae (r = 0.3373 d−1, 0.3317 d−1; λ = 1.4011 d−1, 1.3934 d−1; R0 = 73.2 offspring, 68.1 offspring) after feeding on a honey diet. We conclude that carbohydrate-rich diet significantly enhanced the biological control efficacy of Trichogramma, but the performance differed among different species. The results of this study contribute to improving the efficient application of Trichogramma parasitoids in the field.