Entomopathogenic nematodes (EPNs) of the genera Steinernema and Heterorhabditis occur naturally in soils throughout the world where they parasitise different life stages of various soil-inhabiting insects. The nematodes are synergistically associated with bacteria and together they kill and utilise their insect host. Infective juveniles (IJs) are the only free-living stage of nematodes found in soil and carry the bacteria in their intestines, releasing them once the body of the host is penetrated. They kill their hosts within 48 hours, can be produced commercially and can be applied with standard spraying equipment or through certain types of irrigation systems. The main interest in these nematodes is their potential as biological control agents in integrated pest management systems.
A survey is currently being undertaken in the north-eastern parts of South Africa to establish whether any endemic EPNs can be found in these areas. Soil samples were collected in litchi, macadamia, avocado, mango, grenadillas and guava orchards in the different production areas. Soil samples from undisturbed natural soils were also collected. Samples were transported to the laboratory where the soil was baited with mealworms to collect EPNs from the soil. Mealworm (Tenebrio molitor) larvae showing signs of EPN infection after 7-14 days were placed on white traps to collect the EPNs. EPNs emerging from the mealworm cadavers were send to the University of Stellenbosch for DNA identification. Thirty eight samples have been collected in the Mpumalanga Province and nine in the Limpopo Province. Nine of the samples were taken from litchi orchards and three of them tested positive for entomopathogenic nematodes. The survey will continue and samples will also be taken in the production areas of KwaZulu-Natal and Eastern Cape provinces.