I hate to be the bearer of bad news, but, it is that time of the year where we start to see beetles eating their way through our prized garden plants. Two of the most common and destructive beetles we see in our ornamental plantings - trees, shrubs, and perennials - are the rose chafer and Japanese beetles. The rose chafers are the first to appear during the summer.
The rose chafer, Macrodactylus subspinosus (Fabricius), is a tan, long-legged slender beetle from 8-12 millimeters long. The rose chafers damage plants by feeding on the flowers, newly-set fruit and foliage. On roses, it skeletonizes the leaves in the same way as other scarab beetles like the Japanese beetle. It feeds on the foliage of many different plants and it is greatly attracted by flowers.
Adult beetles emerge from the soil in late May through early June and they live for about one month. Mating occurs soon after emergence and the females lays 24 to 36 eggs continuously for about two weeks in the soil in grassy sandy areas. Upon hatching, the larvae burrow in the soil and feed on the roots of grasses and weeds. They overwinter as a larvae and continue development in the spring. The full-grown larva or grub is white and measures up to 18 mm in length. Pupation occurs in the spring. Luckily, for us, the rose chafer has only one generation per year.
Rose chafers can be handpicked and destroyed if the infestations are light. Protective barriers made from cheese cloth or row cover can also be used to keep the beetles off of your prized plants. Rose chafers can be very numerous especially in areas with sandy soils. In these cases, insecticides may not give satisfactory control as rose chafers can move in from surrounding untreated areas or the insecticides do not seem to prevent feeding activity for very long. However, after about two to three weeks of heavy damage the beetle numbers appear to subside.
One interesting fact about rose chafers is that the beetles have a chemical that affects the heart of small, warm-blooded animals. Because of this, rose chafers should not be fed to your backyard chicken flock.
Next week, I'll write about Japanese beetles. These guys will be making their yearly appearance after the rose chafers.
Anne Lenox Barlow is a professional horticulturist who enjoys gardening with her family in Plattsburgh. She also chronicles her gardening experiences at her blog www.northcountrygarden. wordpress.com. She can be reached at firstname.lastname@example.org.