The fungus Metarhizium rileyi as a control agent for the African armyworm

During the inspection of kikuyu grass pastures in KwaZulu-Natal, cases of African lawn moth larvae mortality were recorded. The cause was the soil-dwelling fungus Metarhizium rileyi. The researcher discovered that the dead insects, found predominantly on grass stems and the soil surface, were covered in white and green conidia — asexual spores of the fungus.

Previously, this fungal species had already shown efficacy as a biological control agent against related insect species, in particular against the fall armyworm in the Philippines. The case in KwaZulu-Natal became the first documented observation of this organism's efficacy against the African lawn moth.

This pest poses a serious threat to agriculture, causing poisoning in livestock animals grazing on infested kikuyu grass. Clinical signs of intoxication in animals include abdominal pain, dehydration, excessive salivation, impaired coordination, as well as respiratory and cardiovascular system problems. Animals may mimic drinking without consuming water when attempting to quench their thirst.

Today, the fungus Metarhizium rileyi is considered a promising component for the development of new plant protection strategies. Further steps in this direction include organizing commercial production of this fungal species and its subsequent registration as a biopesticide. The introduction of such a product could supplement existing pest control methods during periods of mass insect outbreaks in South Africa and other regions of the world.