NEMATODES AND NEMATOMORPHS AS CONTROL AGENTS OF GRASSHOPPERS AND LOCUSTS

The relationship of nematodes and nematomorphs with grasshoppers and l ocusts is reviewed, emphasizing the actual or potential role of these parasitoids in microbial management. There are records of mermithids p arasitizing grasshoppers worldwide, and they are considered important biological control agents in some grassland ecosystems of Europe, Nort h and South America, Papua New Guinea, New Zealand, and Australia. Nem atomorphs, although widely distributed, are uncommon parasitoids of gr asshoppers, and their dependence on free-standing water for host infec tion and apparent host specificity are considered drawbacks to their u se in biological control programmes. The ascaridids, spirurids, and ac anthocephalans are parasites of birds and mammals, and may use grassho ppers as intermediate hosts. They have been shown to debilitate grassh opper hosts in laboratory studies, but their primary role as parasites of vertebrates precludes any consideration as biological control agen ts. Rhabditids do not naturally parasitize grasshoppers, but recent ad vances in mass-culturing techniques have given them a potential role a s bioinsecticides for the control of grasshoppers. Quantitative data o n the effects of nematodes and nematomorphs on agricultural pests, inc luding grasshoppers and locusts, are generally lacking. However, there is evidence that some, particularly mermithids, are important in the population dynamics of grasshoppers and locusts. Keys to the identific ation of the Various 'worms' found in grasshoppers and locusts are pro vided, including keys to the species of mermithids.