Can beneficial nematodes help control Japanese beetles?
Question:
I have read that beneficial nematodes may be helpful in controlling a Japanese beetle infestation that is attacking my vegetables, flowers, and shrubs. If so, what kind should I be looking for? Where can I get them? How are they applied?
Answer:
Here’s information from Maine’s YardScaping Program, including links to a nematode fact sheet and where you can purchase nematodes.
“Heterorhabditis bacteriophora (Hb) nematodes are most effective against Japanese beetles, European chafers, and other grubs that are lawn pests. They are more efficient than the Steinernemacarpocapsae. Nematodes are shipped in the infectious juvenile stage of their life cycle and can be stored unopened in the refrigerator for up to 2 – 3 weeks. They may come on a sponge, in gels, granules, or liquids. The best time to apply nematodes depends on the weather and grub species. Mid to late August is usually about right. The nematodes are neutralized by exposure to strong sunlight, so they must be applied in heavily overcast or rainy conditions; at dusk or during rainfall is an ideal time. Nematodes prefer a moist environment. If the ground is very dry, it helps to pre-irrigate the area with at least 0.5 inches of water.”