Entomopathogenic Nematodes
Entomopathogenic nematodes are microscopic roundworms that enter insect larvae and kill them with symbiotic bacteria within two to three days. They are the actives in Vegalab Larva BioControl (Steinernema carpocapsae) and Mosquito BioControl (Heterorhabditis), and they only work where the substrate stays moist and shaded.
How they kill
The infective juvenile stage is the only free-living stage. It enters a host through the mouth, anus, spiracles or, in Heterorhabditis, directly through thin cuticle. Inside, it releases symbiotic bacteria, Xenorhabdus for Steinernema and Photorhabdus for Heterorhabditis, which multiply and kill the host by septicemia. The nematodes feed on the bacteria and host tissue, reproduce, and release a new generation of infective juveniles into the substrate. Adult insects and hard-bodied pests are poor hosts; larvae in moist habitats are the target.
Two foraging strategies
Steinernema carpocapsae is an ambusher. It waits near the surface and attacks mobile larvae that move past, which suits litter and surface layers. Heterorhabditis species are cruisers that move through the substrate and respond to host cues, which suits deeper or water-associated habitats. Matching species to habitat is the most important choice in any program, and it is why Vegalab uses different species for fly larvae and mosquito programs. Neither strategy finds hosts inside dry, compacted material.
Where they fail
Infective juveniles die quickly when dry, exposed to UV, or held at high temperature. They do poorly in hot, dry poultry litter, in fresh manure with high ammonia, and in chlorinated or strongly alkaline water. Storage life is limited and cold chain matters. Treat nematodes as one layer in an integrated program alongside sanitation, moisture control and manure management, not as a stand-alone fix. Application timing therefore matters: evening application, prewetted substrate and prompt use after mixing all improve survival of the applied population.
Regulatory position
In the United States, nematodes used as biological control agents are exempt from FIFRA registration, while products still must be accurately labeled. Other jurisdictions regulate them differently. Vegalab Larva BioControl and Mosquito BioControl are currently labeled for crop and plant use; premise and farm water uses are in development pending label review and state acceptance. Any use on a farm site must follow the label that covers that site, and states may add their own requirements for biological products sold across their borders.
Key facts
- Biological control agents other than certain microorganisms, including nematodes, are exempt from FIFRA registration requirements (40 CFR 152.20(a)).
- Steinernema and Heterorhabditis carry mutualistic bacteria of the genera Xenorhabdus and Photorhabdus that kill the insect host (Kaya and Gaugler 1993, Annu Rev Entomol 38:181).
- Nematode species differ in foraging strategy, from ambushers such as S. carpocapsae to cruisers such as Heterorhabditis (Lewis et al. 2006, Biol Control 38:66).
- Vegalab Larva BioControl contains Steinernema carpocapsae; Mosquito BioControl contains Heterorhabditis (Vegalab product labels).
How our delivery technology applies
Infective juveniles fail from desiccation and UV long before they fail from lack of hosts. Encapsulating nematodes in a hydrated biopolymer matrix buffers moisture loss and shields them from light during application, then softens in wet substrate to release them where larvae live. The shell cannot make dry litter habitable, but it can widen the application window and reduce losses between tank and target.
Farm managers: request a nematode trial protocol for your manure or water system.
Related reading
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