Heterorhabditis bacteriophora
A microscopic roundworm, 0.4–1.5 mm long, sold by the million to spray or water onto lawns against white grubs. It actively hunts for its host. The infective juveniles move through moist soil, get into a grub and release bacteria that kill it, then breed inside the body. It is one of the best-studied biological grub controls, but field results are inconsistent. It works only on moist soil that stays above about 12 °C for two weeks, and only if it is watered in straight away.
At a glance
- Mode
- Insect-parasitic nematode + Photorhabdus bacteria
- Rate
- 250k–500k /m²; BASF: European chafer 0.5–1 million
- Soil temp
- 12–30 °C (BASF); Koppert: active 16–35, best 19–33; RHS 12–20
- Timing
- Late summer, on young grubs near the surface
- Storage
- Fridge, 2–6 °C; never frozen
- Shelf life
- 2 to 6 weeks from delivery, by supplier
How it works
What arrives is the infective juvenile, the one stage that lives outside a host. Heterorhabditis is a cruiser: it moves through the soil looking for hosts rather than waiting for one to pass. It gets into a grub through the mouth, anus or spiracles, and can also bore straight through the body wall. Inside, it releases symbiotic Photorhabdus bacteria, and the grub dies within hours to days. The nematodes feed and breed in the body, and a new generation of juveniles leaves to find more hosts. Grubs killed this way turn red and go gummy, which is the sign to look for when you dig.
Most failures come from the way it is applied rather than from the nematode. It needs a film of water to move and dies in sunlight and dry soil. The soil must be moist before it goes on, it must be watered in immediately, and it has to stay moist for about two weeks. Cornell calls it a warm-temperature nematode with reduced efficacy below 20 °C. Even when it is applied well, field results vary: Tennessee nursery trials recorded 0–75% control of young Japanese beetle grubs from biological treatments, against 83–100% for imidacloprid applied in May to July. Kentucky Extension calls it much less reliable than conventional insecticides.
Is it established?
What a working application looks like. No supplier publishes a schedule, so this is an editorial reading of the kill time and the grub cycle: judge it by a dig, not by the lawn's colour.
- DAYS 2–7Dead grubs in a dug square foot are red to brick-coloured and gummy, not grey and rotting
- WEEKS 2–3Dig the same spots again. Fewer live grubs per square foot than before treatment
- SPRINGIf counts are still above threshold, the grubs are now large and hard to kill. Plan for next August
Release & handling
Nematodes are alive and do not keep. Refrigerate them on arrival, never freeze them, and use them by the date on the pack. Suppliers quote 14 days (Arbico), up to 3 weeks (Buglogical) or about 6 weeks (Koppert). Mix and apply on the same day, onto turf that is already moist, early in the morning or in the evening.
Fridge, 2–6 °C
BASF says 5 °C. Leave air around each tray or pack. Never freeze, and do not use packs past their date.
Water the lawn first
Soil must be moist when the nematodes go on. BASF calls applying before, during or after rain highly desirable.
Cool water, keep it moving
At least 2 L of water at 15–20 °C per sachet (Koppert), or 1 L per tray (BASF). Keep it agitated. Never store the mix.
Dusk or early morning
Out of direct sun. Remove filters of 50 mesh or finer (BASF); Koppert says no finer than 0.3 mm. Nozzles at least 0.5 mm. Keep pump pressure low: Purdue says no more than 50 psi, BASF's ceiling is 300 psi.
Water in at once
BASF: at least 3 mm (1/8 in) within 30 minutes in hot, dry weather; BASF UK: 3 L/m². Keep moist for two weeks.
Pesticide sensitivity
Compatibility varies by product and formulation; check the supplier's table before a tank mix. Imidacloprid combined with H. bacteriophora has worked synergistically against grubs in Rutgers trials. 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 count is under the threshold for your grub species — healthy turf outgrows a few grubs, so leave it
- Soil will fall below about 12 °C within two weeks — below BASF's range the nematodes work poorly
- You cannot keep the lawn moist for two weeks — the nematodes die as the soil dries
- It is spring and the grubs have overwintered — Kentucky Extension calls them large and hard to kill; plan for late summer
- The damage is to leaves, from adult beetles — the nematode only reaches grubs in the soil; see Japanese beetle
- You need dependable control on high-value turf — extension services rate the soil insecticides as more reliable
Where to buy
Suppliers listed alphabetically, not ranked. helpfulbugs takes no commission and does not sell nematodes.
- Arbico Organics (NemaSeek Hb)5M to 500MUS
- BASF (Nemasys G)50M / 250M traysUS / CANADA
- BASF (Nemasys Chafer Grub Killer)50M, treats 100 m²UK
- Buglogical (Hb nematodes)10M to 500MUS
- Koppert (Larvanem)50M / 500M / 2,500MGLOBAL
Heterorhabditis bacteriophora by target
Rate and timing differ by what you are releasing it against. Each page below is the program for one pest.