Japanese Beetle Control Tips for HomeownersUnlike any other garden insect, Japanese beetles have palatability to a wide range of host species – birch, linden, crab apples, poplars, Norway maple, Japanese maple, horse chestnut, American elm, beech, roses, grapes, apples, peach, plum, cherry, raspberry, blackberries, beans, asparagus, peppers, rhubarb, etc. They feed on the upper surface of the leaves and chew the tissues between the veins, giving a skeletonized appearance. During its peak season in July, it can skeletonize an entire tree to bare-bone in a week. Roses are one its top three favorites causing damage to the flowers and leaves. Japanese beetles are strong fliers, posing a huge challenge to prevent its invasion. In the last five years, its population has been widespread in and around Green Bay area, including Bellevue. Besides its foliage damage, the grubs of the beetle can damage turf grass in fall and spring.
Here are some simple control tips for Japanese Beetles:
- Protect your small plants using a floating row cover during afternoon hours, or the beetles can be handpicked and drowned in soapy water.
- On vegetable and fruit crops, the use of organic products like neem oil and spinosad (Bullseye, Monteray Garden Spray, Entrust) can help in preventing the beetle attack. However, these products have a short residual activity and need a weekly application. Please read the label before applying any of these products.
- On small ornamental plants, a complete foliar application of outdoor garden insecticides like carbaryl (Sevin), malathion, imidacloprid, permethrin, or bifenthrin can have maximum effectiveness when sprayed during afternoon hours. Repeated application may be needed once every 5 to 10 days. Read the pesticide label for instructions.
- Use of systemic insecticides like imidacloprid (Merti, Bayer Advanced Tree and Shrub Control) can be effective if it is drenched at least 20 days prior to the beetle attack on small ornamental plants.
- On large trees, there are no effective means to prevent the beetle attack. However, large trees are able to withstand the feeding damage of the beetles, and the defoliated trees will recover next year.
- In lawns, application of a preventive insecticide using imidacloprid (Merit) or halofenzide (Grub B-Gone) before the end of July can prevent the hatching of eggs emerging in early August. Curative insecticides like carbarly (Sevin) should be applied in late August to control emerging young grubs. It is important that all preventive and curative grub control products are watered in with sufficient irrigation or rainfall after application to achieve their effectiveness.