Steinernema carpocapsae
A microscopic insect-killing roundworm, sold by the million and sprayed or watered onto moist soil. Unlike the cruising species, it does not search through the soil: it waits at the soil surface, standing on its tail, and attaches to insects that crawl past. That makes it the nematode for pests that are active on the surface, such as cutworms, armyworms, sod webworms, billbugs and flea larvae in the garden. The same habit makes it a poor choice against white grubs, which stay deeper in the soil.
At a glance
- Mode
- Insect-parasitic nematode + bacteria; ambusher
- Rate
- 250k–500k /m²; 1 billion per acre
- Ships as
- Juveniles on sponge, in gel or powder
- Temp
- Active 14–34 °C; best 19–31 °C
- Storage
- Fridge, 2–6 °C; 3 days to 6 weeks for retail packs
- Water
- Moist soil before; at least 1/2 inch (13 mm) after
How it works
What arrives is the infective juvenile, the one stage that lives outside a host. S. carpocapsae is an ambusher. Instead of moving through the soil after prey, it waits at or near the surface, standing on its tail with most of its body in the air, and attaches to an insect that brushes past. It enters through the mouth, anus or breathing pores and releases symbiotic bacteria, and the host dies within a day or two. Insects it kills are limp and turn yellow to brown. The nematodes breed inside the cadaver, and within two to three weeks hundreds of new juveniles leave it to find the next host.
The ambush habit decides what it controls. It works on insects that move through the thatch and top layer of the soil: cutworms, armyworms, sod webworms and billbugs in turf. It also works on cat flea larvae and pupae in the shaded, moist outdoor spots where they develop. In North Carolina tests it killed more than 90% of flea larvae within 24 hours at 1 billion per acre, and in Louisiana 91–97% of flea pupae in their cocoons. It is a poor match for white grubs, which move slowly through the root zone. The early trials that wrote nematodes off against grubs used this species, which was a mismatch for the ambush habit. Turf researchers now use cruising species such as Heterorhabditis bacteriophora for grubs.
Is it established?
Nematodes leave little to see. The dead larvae are hard to find, so the reliable check is a bait insect. PNW Extension's test uses waxworms, sold as fishing bait.
- DAY 0Bury 3–4 tea strainers, each holding 2–3 waxworms, about 10 cm deep in the treated area
- DAY 1–2Target larvae start dying; the host dies within a day or two of infection
- DAY 2Lift the strainers, rinse the waxworms and keep them on damp paper, in the dark
- DAY 3–12Infected waxworms turn yellow, tan or brown. Black ones died of something else
Release & handling
Nematodes are alive, and how long they keep depends on the formulation. Refrigerate them on arrival at 2–6 °C, never freeze them, and use them by the date on the pack. Retail packs quote anything from three days (Buglogical's 10-million sponge) to six weeks (Koppert Canada); Koppert's professional product averages two to three months. Apply late in the day or when it is overcast, onto moist soil, then water them in straight away: direct sun kills them within minutes.
Fridge, 2–6 °C
Check that the pack is not warm. Never freeze it. Use it before the date.
Water the soil first
Moist, not waterlogged. After a dry spell, rake through the crust and irrigate 10–15 cm deep. Pre-water to cool soil above 29 °C.
Evening, plenty of water
8–24 L per 100 m² (2–6 US gal per 1,000 sq ft). Remove filters finer than 50 mesh; keep pressure under 20 bar.
Water in at once
At least 1/2 inch (13 mm) straight after, to wash them off the grass into the thatch. Then keep the soil moist; suppliers say for anything from one to four weeks.
Pesticide sensitivity
Nematodes tolerate most herbicides and fungicides but are killed by some insecticides and nematicides. PNW Extension also warns against mixing them with nitrogen fertilisers, particularly urea. Check the supplier's list before a tank mix. Check a product →
When to choose something else
An honest boundary is more useful than a sales sheet. Reach for a different approach when:
- The pest is white grubs or Japanese beetle larvae — S. carpocapsae is a poor match; turf researchers use Heterorhabditis bacteriophora instead
- The fleas are indoors — the tests that worked were in moist lawn and soil outdoors, not the carpets and pet bedding where larvae also live, so indoor fleas need a different approach
- The target is fungus gnats in compost — Steinernema feltiae is the species sold for them and keeps working in cooler compost
- Soil is below about 14 °C — Koppert gives 14 °C as the bottom of its active range; wait for warmer soil
- You cannot keep the ground moist after treatment — in dry or sun-baked soil the nematodes die before they meet a host
Where to buy
Suppliers listed alphabetically, not ranked. helpfulbugs takes no commission and does not sell insects.
- Arbico Organics (NemAttack Sc)5M to 500MUS
- Buglogical10M to 500MUS
- Koppert (Capsanem)50M / 500M / 2,500MGLOBAL
- Natural Enemies (Capsanem)50M / 500MUS
- Sound Horticulture1M to 250MUS
Steinernema carpocapsae by target
Rate and timing differ by what you are releasing it against. Each page below is the program for one pest.