Successes and failures in the use of parasitic nematodes for pest control

Advances in mass-production and formulation technology of entomopathogenic nematodes, the discovery of numerous isolates/strains and the desirability of reducing pesticide usage have resulted in a surge of scientific and commercial interest in these nematodes. The lessons learned from earlier problems have encouraged scientists and leading commercial companies to increase their efforts toward improving cost efficiency and better product positioning in the market within the confines of product capabilities. The successes or failures of the nematodes against 24 arthropod pest species of agriculture and animals and against a major slug pest in agriculture are discussed in this review. Commercial successes are documented in markets such as citrus (Diaprepes root weevil), greenhouses and glasshouses (black vine weevil, fungus gnats, thrips, and certain borers), turf (white grubs, billbugs, and mole crickets), and mushrooms (sciarid flies). In addition, the successful commercialization of a nematode (Phasmarhabditis hermaphrodita) against slugs in agricultural systems is presented. Despite this progress, the reality is that nematode-based products have limited market share. Limited share is attributed to higher product cost compared to standard insecticides, low efficacy under unfavorable conditions, application timing and conditions, limited data and cost benefit in IPM programs, refrigeration requirements and limited room temperature shelf life (product quality), use of suboptimum nematode species, and lack of detail application directions. One or more of these factors affected the market introduction of the nematodes despite promising field efficacy against insects such as black cutworm in turf, sugar beet weevil in sugar beet, sweet potato weevil in sweet potato, and house fly adult in animal-rearing farms. Insects such as cabbage root maggots, carrot root weevil, and Colorado potato beetle are listed on the label of certain commercial products despite low efficacy data, due to insect susceptibility, biology, and/or behavior. To make entomopathogenic nematodes more successful, realistic strategies through genetic engineering, IPM programs, and new delivery systems and/or training programs to overcome their inherent cost, formulation instability, and limited field efficacy toward certain insects are needed.