The adult of the white grub is the Japanese Beetle, May beetle or June beetle. The larva, which is "C"-shaped with a white body and tan or brown head, produces damage to lawns and gardens. The larvae feed on grass roots causing yellow spots and patches on lawns. The adult beetles feed on over 275 plant species including roses, other ornamentals, all deciduous fruit trees, many small fruits, vegetables, grasses and weeds.
A fully-grown larva is 20 to 25 mm long, and dark-colored. Two rows of minute hairs on the underside of the last segment distinguish white grubs from similar-looking larvae. White grubs overwinter as larvae and are ready to start feeding on roots as the soil warms up in the spring. Depending on the species, a life cycle may require one, two, or more years. Damage results from larvae feeding on roots. The most obvious and significant damage occurs during the spring and summer.
Controlling Grubs - Larvae Control
- Treat with a combination of Milky Spore and NemaSeek beneficial nematodes in either the spring or the fall. The nematodes help to distribute the Milky Spore. This combination of organisms also works synergistically to most effectively control the grubs. Milky Spore only has to be applied once.
- Treat again with NemaSeek Beneficial Nematodes six months after your first application to further distribute the Milky Spore and to eliminate newly developing grubs.
Adult Beetle Control
Direct spray applications of insecticidal soap will kill Japanese Beetles on contact but does not provide any residual protection. Pyrethrum is the best organic insecticide treatment against Japanese Beetles.
- Large Area Beetle Control: Use PyGanic EC 1.4. This is a pyrethrum concentrate that is effective against hundreds of insects, including the Japanese Beetle. If the water in the area to be treated is alkaline, you would have to consider adding Citric Acid to lower the pH to a mid-range of 5.5 -7.
- Small Areas and Garden Beetle Control: Use Safer BioNeem (a combination of insecticidal soap and Neem oil) However, please keep in mind that Neem can be damaging to plants that are herbaceous or "sensitive," and in those situations, you would have to use a Pyrethrum.
Related Article: Japanese Beetles - Beetle Mania.