How to Manage Pests

Pests in Gardens and Landscapes

Nematode application tips

You must choose a nematode that is effective for your pest as indicated under active ingredient. Purchase nematodes from a reputable source that has properly stored the product and will supply you with the correct species. Nematodes are highly perishable and must be used immediately and applied during early evening when sunlight is at a minimum and soil temperatures are not too hot.

Nematodes function best with soil temperatures between 60° and 93° F. Do not mix nematodes with hot water; use cool to lukewarm water. They must be applied when the susceptible larval stage of the pest is active. Repeat applications may be necessary. Monitor for killed larvae. Insects infected with Steinernema turn brownish yellow; those killed by Heterorhabditis turn brick red to purple. Infected insects may be active for a few days and may not die for 2 to 5 days after treatment.

For soil treatments, irrigate area to be treated, mix nematodes with water according to the label directions, and drench the soil, agitating the mixture continuously. Watering the soil afterward helps to move nematodes deeper in to the soil, but care must be taken not to flood the soil so that standing water remains, because nematodes cannot infect if too much water is present. Irrigate again in 3 to 4 days to keep soil moist.

Applying nematodes
Applying nematodes to trees for controlling pests

For treating carpenterworms and clearwing moths, apply to trunk or branch burrows when larvae are active and pushing out frass, usually in summer. Mix nematodes with distilled water in a squeeze bottle at a rate of about 1,000,000 to the ounce, insert the tube as deeply as possible, and squirt directly into the hole. Continue to apply until the water dribbles out. Agitate the applicator frequently. Mark the tunnel entrance with a bit of grafting wax and check it in about a week to see if the larvae have pushed out more frass before dying. Plug frass-filled holes with wax, spray with colored paint, and return 1 week later. If frass continues to be pushed out, the larvae were not killed and you should reapply nematodes. You may want to purchase a fresh batch.

Statewide IPM Program, Agriculture and Natural Resources, University of California
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Agriculture and Natural Resources, University of California

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