Garden Pest Avengers

Got white grubs, fleas and fungus gnats?? Get beneficial nematodes. They’ll attack these insect pests, but are harmless to humans, plants and pets.

Spring is well underway and warm temperatures are getting many insects into the swing of their life cycle. For fleas, white grubs, or fungus gnats, the crucial part of the life cycle occurs in the warm, moist soil during the larval and pupal stages.

White grubs feed on the roots of grasses and plants from late May through August or September before going deeper in the soil during fall and winter. Flea larvae develop in the soil where pets sleep and lounge. Fungus gnats become a problem for indoor container plants that have been overwatered by their owners.

Both of these insect stages are vulnerable to a natural and living predator that’s available to purchase: beneficial nematodes.

At first glance, the word “nematode” strikes fear into the average gardener because there are species of nematodes that cause root knots and plant damage. However, beneficial nematodes are microscopic soil worms that can be purchased online or at local nurseries and watered into the lawn to attack white grubs, flea larvae, fungus gnats and other insects (like termites) in the soil. They are harmless to humans, plants and pets. Nematodes are a living organism and must be treated with care by keeping them out of sunlight and extreme heat.

Here are some crucial elements when using beneficial nematodes:

  • Adequate soil moisture is a MUST — it doesn’t have to be wet, just moist. Nematodes are so tiny that they need to be able to SWIM in the moisture that occurs between soil particles. Dry soil results in poor nematode survival and performance.
  • Measure the area to be treated and be sure to purchase enough nematodes per label directions.
  • Time of treatment is crucial: apply nematodes in late evening when sunlight is low and soil temperatures are cooling down. Grubs will be higher in the soil and flea larvae will be active.
  • For container plants, mix the recommended amount of nematodes with a gallon of water and water them into the potting soil. Only water container plants when the soil is dry down to about 1 inch deep.

Note about termites: termites are found everywhere. They’re in every yard and doing their job as nature intended: eating and breaking down cellulose and wood in the soil. Termites find houses because there is wood to soil contact at the house, or a trail of water (usually a leak or dripping outside faucet) in the soil that leads them to the house. While a nematode yard treatment for termites won’t likely result in termite colony death, a treatment of nematodes around the house foundation may reduce termite numbers locally.

If you have areas of grass that are always stressed because of thin soil, too much sunlight and the like, consider taking advantage of the SAWS WaterSaver Landscape Coupon or Patioscape Coupon. These coupons allow you to replace 200 square feet of grass at a time with beautiful landscape beds or patioscape living areas.

Picture of Nathan Riggs
Nathan Riggs
Nathan Riggs is a SAWS project coordinator and licensed irrigator who also happens to have a degree in entomology from Texas A&M University. Yes, Nathan’s a bug expert, and not just on water bugs! When he’s not hard at work on SAWS conservation projects, he enjoys a wide variety of interests including: landscaping, hiking, photography of flowers, insects and other critters, and planning his next adventure with his wife Ella and family.
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