Efficacy of Entomopathogenic fungus Aspergillus nomius against Dolichoderus thoracicus

Abstract

The ant pest Dolichoderus thoracicus (Smith) (Hymenoptera: Formicidae) has experienced population increases in Taiwan recently and has been shown to invade human settlements frequently. In addition, D. thoracicus has been found to be naturally infected by the fungus Aspergillus nomius Kurtzman et al. (Eurotiales: Trichocomaceae). Entomopathogenic fungi find it difficult to colonize social insects because of the challenge of penetrating the insect cuticle and because of social behaviors, including grooming, that eliminate invaders from the nest. However, A. nomius can evade these defenses and spread within the ant colony. In the present study, ant mortality increased in a dose-dependent manner upon cuticular infection with A. nomius conidia. Among four Aspergillus spp. examined, A. nomius was more virulent to worker ants and was the only fungus to produce conidia on the ant host. Allogrooming potentially promotes conidial invasion and spreading among hosts in a colony because ants treated with conidia on the cuticle increased the mortality of other members in the nest. Assessment of chitinase, esterase, and lipase activity suggested that A. nomius efficiently exploited the host for nutrients. Because A. nomius can cause human infections and environmental consequences, further studies are required to assess the potential impacts of utilizing A. nomius to control outbreaks of D. thoracicus.