Scanmask Topdressing

For most pests, and for a general or preventative treatment, you can apply Scanmask anytime the soil is not frozen. Some pests have a best window; for example, cabbage root maggots are treated from March to June, when you plant. The treatment calendar lists the timing for each pest.

The nematodes in Scanmask stay active in soil as cool as about 55°F (that's the soil temperature, which can differ from the air temperature), so Scanmask works well in early spring and fall.

Apply at dusk if you can, or in the late afternoon or evening. Sunlight and heat harm nematodes.

As a topdressing (recommended):

1. Add 1 cup of water to the nematode container and let it sit for 30 minutes at room temperature.
2. In a bucket, mix peat moss, vermiculite, sandy humus, or potting soil with water: 5 quarts with 2 quarts of water for the Lawn & Garden size, or 4 gallons with ½ gallon of water for the Horticultural size.
3. Add the contents of the container to the mixture, then rinse the container with ½ cup of water and add that too.
4. Mix thoroughly so the nematodes are spread evenly through the moist mixture.
5. Water the area to be treated.
6. Spread the mixture by hand over the affected areas, add it to seed furrows, or put it around transplants. The Lawn & Garden size treats about 400 sq ft, and the Horticultural size about 1,000 sq ft. Use all of the mixture within 24 hours of mixing.
7. Water again afterward to wash the mixture off the leaves.

To spray it instead, mix the contents with cold water (2 gallons for Lawn & Garden, 1 gallon for Horticultural), let it sit 30 minutes so the carrier floats, skim the carrier off with a fine strainer, and apply the liquid with a pump sprayer or watering can with any fine filters removed. Spread the 2 gallons (Lawn & Garden) over about 400 sq ft, or the 1 gallon (Horticultural) over about 1,000 sq ft. See How to apply for more tips.

Put the container in the refrigerator right away, and use it before the date on the package. Never put it in the freezer. The cold packs in the box don't need to still be cold when it arrives. See Shipping and arrival.

The nematodes in Scanmask occur naturally in soil and haven't been modified in any way. They are harmless to people, pets, and plants, and the US Environmental Protection Agency (EPA) has exempted them from the registration required for chemical pesticides. The carrier they come in isn't meant to be eaten and may upset the stomach, so keep the container away from children.

Scanmask works alongside many common herbicides, insecticides, fungicides, and other biological controls, but some need to be applied a week or two apart; see the chemical compatibility list on our How to apply page.

They contain the same nematode. The topdressing comes in a moist, soil-like carrier that you mix with peat moss, vermiculite, or potting soil and spread by hand, which protects the nematodes from heat, sunlight, and drying out. It also keeps much longer in the fridge. If you'd rather spray, we recommend Scanmask Spray.

Yes. The directions include pump sprayer and watering can steps, where you soak the contents in water and strain off the carrier. For spraying, though, Scanmask Spray is easier.

Yes. Beneficial nematodes don't harm people, pets, plants, or beneficial creatures like bees, earthworms, and ladybugs. The EPA exempts them from pesticide registration.