A dull, metallic green beetle with brown wings has been destroying the blossoms of roses, peonies and other flowering plants. This culprit is the false Japanese beetle, which emerges and feeds in late June and July. False Japanese beetles typically feed on the blossoms of many plants but may also feed on foliage and fruit. They are particularly fond of rose flowers, especially white or light-colored blossoms. Other favored flowers include blackberry, clover, coreopsis, hollyhock, honeysuckle, iris, lilies and light colored petunias. Peas, beans, cantaloupe, corn and cucumbers appear to be on their list of favorite vegetables. False Japanese beetles overwinter as larvae in the soil of grassy, sandy areas and emerge as adults in late June or early July. The false Japanese beetle’s head and thorax is a dull, metallic green and its wings are brown. False Japanese beetles mate, lay eggs and feed in the garden for a couple of weeks. They cause most of their damage within a two-week period, and are generally gone by the end of July. Control methods may depend on population levels of false Japanese beetles and your tolerance for cosmetic damage to the plants. If only a few plants are affected, handpick the adults and kill them by dropping them into a pail of soapy water. The beetles are strong flyers and can continue to move into the gardens making continuous vigilance during July necessary. To prevent flower damage to high value plants, cover them with a light fabric like cheesecloth. If physical methods do not provide satisfactory control, use a residual insecticide such as carbaryl (Sevin) or permethrin (Eight). However, even using an insecticide may not be completely effective, as the insecticide residues may not control new beetles that enter the garden. To avoid killing large numbers of beneficial insects, you may want to focus insecticide sprays on high value plants. The best time to apply an insecticide is early in the morning or late at night when bee activity is minimal. Although seeing our flowers destroyed by false Japanese beetles is very disappointing, we can take some comfort in knowing that we currently do not have Japanese beetles in the area. The Japanese beetle is a much more serious landscape pest that destroys both garden plants and lawns.
