Biocontrol of Leucoagaricus gongylophorus by Trichoderma asperelloides with implications to ant mini-colony survival

Abstract

Leaf-cutting ants (LCAs) of the genera Atta and Acromyrmex are major agricultural pests in the Americas, relying on their mutualism with the fungus Leucoagaricus gongylophorus for colony survival. Mycoparasites such as Trichoderma spp. offer promising biocontrol tools by antagonizing this essential symbiont. This study aimed to identify the most antagonistic isolate of Trichoderma asperelloides, elucidate its mechanisms of action against the fungal garden-symbiont L. gongylophorus, and further evaluate its indirect biocontrol activity on the health and survival of Atta sexdens mini-colonies. Isolates of T. asperelloides namely Tricho 4, Tricho 5, Tricho 7, and Tricho 11 exhibited strong antagonism, reducing L. gongylophorus colony growth by more than 94 % in dual culture assays. Additionally, antibiosis mechanism and volatile compound release by T. asperelloides induced over an 80 % reduction in L. gongylophorus growth. Moreover, exposure to these isolates significantly disrupted ant mini-colonies, leading to mortality rates of up to 60 % and a concurrent reduction in waste production, likely linked to the antagonism effects of T. asperelloides on the garden-symbiont fungus. Overall, these T. asperelloides isolates demonstrate potent antifungal activities against L. gongylophorus and may serve as a sustainable biological strategy for managing LCA colonies.