The Effects of Trichoderma Fungi on the Tunneling, Aggregation, and Colony-Initiation Preferences of Black-Winged Subterranean Termites, Odontotermes formosanus (Blattodea: Termitidae)

Abstract

The black-winged subterranean termite, Odontotermes formosanus Shiraki, is a severe pest of plantations and forests in China. This termite cultures symbiotic Termitomyces in the fungal combs, which are challenged by antagonistic microbes such as Trichoderma fungi. In a previous study we showed that O. formosanus workers made significantly fewer tunnels in sand containing commercially formulated conidia of Trichoderma viride Pers. ex Fries compared with untreated sand. Herein, we hypothesize that fungi in the genus Trichoderma exert repellent effects on O. formosanus. Different choice tests were conducted to evaluate the tunneling and aggregation behaviors of O. formosanus workers reacting to sand/soil containing the unformulated conidia of seven Trichoderma fungi (Trichoderma longibrachiatum Rifai, Trichoderma koningii Oud., Trichoderma harzianum Rifai, Trichoderma hamatum (Bon.) Bain, Trichoderma atroviride Karsten, Trichoderma spirale Indira and Kamala, and T. viride). We also investigated the colony-initiation preference of paired O. formosanus adults to soil treated with Trichoderma conidia (T. koningii or T. longibrachiatum) versus untreated soil. Tunneling-choice tests showed that sand containing conidia of nearly all Trichoderma fungi tested (except T. harzianum) significantly decreased tunneling activity in O. formosanus workers compared with untreated sand. Aggregation-choice test showed that T. koningii, T. atroviride and T. spirale repelled O. formosanus workers, whereas T. longibrachiatum and T. hamatum attracted termites. There was no significant difference in proportions of paired adults that stayed and laid eggs in the soil blocks treated with conidia of Trichoderma fungi and untreated ones. Our study showed that Trichoderma fungi generally repelled tunneling in O. formosanus, but may exert varied effects on aggregation preference by workers.

Effects of clay materials and moisture levels on habitat preference and survivorship of Formosan subterranean termite,Coptotermes formosanusShiraki (Blattodea: Rhinotermitidae)

“…In addition, previous studies showed that soil microbes such as Metarrhizium anisopliae (Metschn.) Sorok and Trichoderma fungi significantly influenced the aggregation and tunneling preferences of subterranean termites (Xiong et al, 2018b;Xiong et al, 2019;Wen et al, 2020). In our study, different microbes may colonize wooden cylinders or baiting containers containing each clay material and soil, and affect termites' choice.…”

Potential of fungi of the genus Trichoderma for biocontrol of Philaenus spumarius, the insect vector for the quarantine bacterium Xylella fastidosa

“…Likewise in mycoparasitism, the interaction of Trichoderma with insects may be associated with production of bioactive secondary metabolites having insecticidal effect 55 or semiochemical activity, thus influencing insect behavior such as oviposition, 56 choice of host plant [38][39][40] or aggregation. 57 These compounds may possibly act synergistically with extracellular enzymes, such as chitinases, proteases and lipases in the course of entomoparasitic and entomopathogenic activities of Trichoderma.…”

“…may act directly through parasitism and entomopathogenic activities, or indirectly by physiological interactions with the plant, which result in the induction of systemic plant defensive responses or attraction of natural enemies or the pest. Likewise in mycoparasitism, the interaction of Trichoderma with insects may be associated with production of bioactive secondary metabolites having insecticidal effect 55 or semiochemical activity, thus influencing insect behavior such as oviposition, 56 choice of host plant 38–40 or aggregation 57 . These compounds may possibly act synergistically with extracellular enzymes, such as chitinases, proteases and lipases in the course of entomoparasitic and entomopathogenic activities of Trichoderma .…”

Trichoderma Species Attract Coptotermes formosanus and Antagonize Termite Pathogen Metarhizium anisopliae

“…This study aimed to investigate whether Trichoderma conidia in soil trigger the aggregation preference by termites. Protocols provided by Xiong et al (2018Xiong et al ( , 2019 were modified to prepare the bioassay arenas. In brief, blocks (40 × 40 × 10 mm [L by W by H]) of soil (sandy clay loam) were made using a plastic mold.…”

“…This study aimed to investigate whether Trichoderma conidia in sand trigger the tunneling preference by termites. Methods provided by Xiong et al (2018Xiong et al ( , 2019 were modified to prepare the experiments. The bioassay arenas consisted of two square acrylic plates (156 × 156 × 3 mm [L by W by H]), which were assembled with four narrow edge strips (156/150 × 3 × 1.5 mm [L by W by H]) to create a two-dimensional tunneling chamber.…”