Monitoring of mutual interference behavior of Trichogramma brassicae (Hymenoptera: trichogrammatidae) over 45 generations of rearing on Angoumois grain moth

Authors: GHAEMMAGHAMI, EHSAN - Tarbiat Modares University; FATHIPOUR, YAGHOUB - Tarbiat Modares University; BAGHERI, ABDOOLNABI - Tarbiat Modares University; TALEBI, ALI ASGHAR - Tarbiat Modares University; Reddy, Gadi V.P.

Submitted to: Neotropical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/11/2021
Publication Date: 11/9/2021
Citation: Ghaemmaghami, E., Fathipour, Y., Bagheri, A., Talebi, A., Reddy, G.V. 2021. Monitoring of mutual interference behavior of Trichogramma brassicae (Hymenoptera: trichogrammatidae) over 45 generations of rearing on Angoumois grain moth. Neotropical Entomology. 51:54-64. https://doi.org/10.1007/s13744-021-00919-6.
DOI: https://doi.org/10.1007/s13744-021-00919-6

Interpretive Summary: Trichogramma species are among the most common natural enemies used for augmentative biological control of agricultural pests. There has been reported more than 200 known species of Trichogramma from around the world, of which 19 species have been mass produced and released for augmentative biological control. Our results showed that the number of parasitized hosts per parasitoid decreased with increasing parasitoid density, a pattern that might be explained by mutual interference. In the current study, there was a strong inverse relationship between parasitoid density and per capita searching efficiency. Although the negative value of the regression slope indicated an inverse relationship between wasp density and per capita parasitism, the slope values increased gradually over generations, showing that mutual interference decreased over generations. This may be because reduction in fecundity and parasitism capacity as well as searching efficiency over sequential generations has been confirmed in our previous studies. In augmentative biological control programs, there is an optimal release rate of biocontrol agents resulting in an effective control of a pest species and avoiding additional intraspecific competition. Avoiding the intraspecific and interspecific completion among biocontrol agents in biological control programs in indoor and outdoor cropping systems is a crucial point that should be taken into consideration.

Technical Abstract: Trichogramma brassicae (Bezdenko) is one of the most common species of natural enemies used in augmentative biological control programs in many countries. Understanding of the foraging behavior of a parasitoid can help us to improve its performance under field conditions. This study is the first assessment of trends in mutual interference behavior of T. brassicae under long-term mass rearing (over 45 generations) on a common factitious host, Sitotroga cerealella (Olivier). Our results revealed that the total parasitism rate of T. brassicae reared on S. cerealella eggs was significantly affected by parasitoid densities and number of generations under continuous rearing. Also, parasitoid density and number of generations in rearing had significant effects on the per capita parasitism rate. Meanwhile, per capita searching efficiencies were different in sequential generations and at different densities. The number of hosts parasitized per parasitoid decreased on day 1 of the experiment with increasing parasitoid density, showing the effect of mutual interference. The linear regression between the natural logarithm of per capita searching efficiency and the natural logarithm of parasitoid density showed an inverse relationship. While the m (interference coefficient) values increased, the Q (quest constant) values had a decreasing trend over 45 generations. The highest (-0.167) and lowest (-0.242) values of m were observed in G45 and G5, respectively. Accordingly, G5 and G45 had the highest (0.053) and lowest (0.023) Q values, respectively. Thus, it seems the negative effects of mutual interference decreased over generations.