Global distribution of entomopathogenic nematodes, Steinernema and Heterorhabditis

Entomopathogenic nematodes (EPNs) in the families' Steinernematidae and Heterorhabditidae are obligate insect parasites. Their easy multiplication, broad host range, compatibility with chemical pesticides, and ease in application has grabbed interest among research practitioners to work on these beneficial microorganisms. Till date, around 100 valid species of Steinernema and 21 species of Heterorhabditis have been identified from different countries of the world. Extensive surveys have been conducted across the globe to isolate locally adapted EPN species and exploit them to suppress soil-dwelling and foliar insect pests in agricultural fields. Most of the new species have been described from Asia, whereas research in some Asian countries are still at infancy. Some new species have been recorded from Australia but very few surveys have been conducted in New Zealand. Likewise, less information about these tiny creatures is from Central America; however, in North America many new species have been described, some of which have been commercialized for insect pest control, whereas in South America, several native nematode species have been described and exploited as biological control agents. European countries have also been explored for EPN diversity and new species have been reported, exploited under field condition, and commercialized. Many new species and other previously described species have been reported from Africa. Despite frequent surveys in different continents of the world, number of sites touched are low and, therefore, further surveys are still needed to explore untouched geographic areas and climatic conditions, both in plantations and indigenous forests with an aim to identify and exploit additional EPN species.