Hb+Sf Nematodes - Description

Heterorhabditis bacteriophora + Steinernema feltiae · How to Say It: het-er-oh-rab-DY-tis bak-teer-ee-OFF-or-uh, or just "Hb"; sty-ner-NEE-muh FEL-tee-eye, or just "Sf"

Grub, Fungus Gnat & Warm-to-Cool Soil Pest Control

Beneficial nematodes for soil pest control

Introduction to the Hb+Sf Mix

Soil temperature isn't the same all the way down. It shifts with depth, season, soil type, and even how much organic matter is breaking down beneath the surface, so a single lawn, greenhouse bench, or raised bed can have cool-season and warm-season pests at the same time. One nematode species built for a specific temperature range might not be as effective. Steinernema feltiae (Sf) stays active in cool soil, while Heterorhabditis bacteriophora (Hb) becomes active as soil warms. Blended together, they can provide effective coverage even when temperature or the weather shifts.

What Beneficial Nematodes Are

Nematodes are microscopic, unsegmented roundworms found in nearly any growing environment. Under a microscope they're translucent and slightly tapered, curling into an S or J shape at rest, and too small to see with the naked eye. Beneficial nematodes are entomopathogenic biological control agents. Instead of feeding on plant tissue, they hunt down insect pests directly, infect them, and let their symbiotic bacteria do the rest. That's the main difference between a beneficial nematode and the plant-parasitic kind that actually damages roots.

Beneficial nematode with a grub

Two Temperatures, Two Depths, One Application

Hb and Sf split both the soil profile and the temperature range between them, rather than competing for the same territory or the same conditions:

  • Sf, cold-active and shallow. Sf stays active in the upper few inches of soil or growing medium, and is more cold-tolerant, remaining effective down to about 46°F (8°C). The combination of shallow range and cold tolerance is what allows it to stay active through cooler shoulder-season conditions.
  • Hb, deep-ranging once soil warms. As soils warm past about 61°F (16°C), Hb actively cruises into the deeper soil profile, tracking hosts rather than waiting for a pest to wander by. That is what makes it effective against grubs and beetle larvae that feed on roots well below where Sf nematodes roam.

Both species follow the same core life cycle. Eggs hatch into non-feeding juveniles, which molt into infective juveniles that hunt down a host, enter its body, and release bacteria that kill it within days. Juveniles feed on the cadaver, and the next generation of adults restarts the cycle. The difference is where each one searches and which temperatures it's active in.

When to Use the Hb+Sf Mix

This blend is great for when you're dealing with more than one soil temperature, more than one type of pest, or wide temperature changes. A few situations where that comes up:

Turfgrass and Lawns. Cool-season pests such as crane fly larvae and certain weevil grubs appear early, while warm-season white grubs like Japanese beetle and chafer grubs build up as soil warms. Sf works in cooler soil; Hb becomes more effective as temperatures rise, extending coverage across the season.

Greenhouses and Nurseries. Potted plants, growing benches, raised beds, and in-ground plots may have cold-tolerant fungus gnat larvae and warm-season root weevils in the same spaces. Since greenhouse temperatures fluctuate, combining nematode species that thrive in different temperature ranges can provide more consistent coverage.

Home Gardens and Mixed Beds. Vegetable, root-crop, and ornamental flower gardens may contain different pests with overlapping generations, including thrips pupae, root maggots, and small grubs. A broader temperature range helps cover pests that are active at different times.

Reapplication Note: Most Hb targets, like grubs, beetle larvae, weevils, and borers, run one generation per season, so one well-timed application can cover the vulnerable stage. Fungus gnats, ants, termites, fleas, and flies are the exception because they reproduce continuously or reinvade. Reapplication on roughly a monthly basis is recommended.

Pairing for Broad-Spectrum Soil-Pest Control

Hb+Sf covers the shallow layer and the deep root zone, so pairing it with a surface-level species closes the remaining gap.

Pairing for Above-Ground Emergence

Some pests spend part of their life cycle in the soil and part above ground.

Safe, Sustainable Pest Management

  • Natural biological control with no synthetic pesticides
  • Safe around people and pets when used as directed
  • Safe for use on edible crops when used as directed, with no waiting period before harvest
  • Fits seamlessly into existing IPM programs
  • Requires no protective equipment