Rose Chafer

Adult rose chafer is a moderate-sized insect, measuring between 5/16-inch to almost 1/2-inch in length. It’s a slender beetle, pale green to tan in color with reddish brown or orangish spiny legs. It has short, lamellate antennae, i.e. a series of flat plate- or page-like segments. A rose chafer sometimes resembles a wasp when it’s flying.The larval stage is called a grub and has a brown head and conspicuous legs. Like other grubs, it’s body is bent into a ‘C’ shape. Fully grown, a rose chafer larva is about 3/4-inch long.

Life Cycle: Females frequently loose more hairs, particularly on the thorax, in the mating process. Eggs of the rose chafer are oval, white, shiny in appearance, and about 0.05 inches long and 0.03 inches in width. Larvae are C-shaped white grubs about 0.8 inches long and 0.12 inches wide when fully grown. Mature larvae have three distinct pairs of legs, a brown head capsule, and a dark rectal sac visible through the integument. Larvae are found in sandy soil feeding on grass roots and can be identified by a distinctive rastral pattern. The pupae are light yellowish-brown in color and have prominent legs. They measure about 0.63 inches in length.

Adult rose chafers become active in northeastern North America from late May to early June. The adults appear suddenly. It seems as though the entire population reaches maturity practically at the same time, and multitudes of beetles suddenly make their appearance. Beetles feed and mate soon after emerging from the soil. It is common to see mating pairs in the newly formed grape clusters. Females deposit eggs singly a few centimeters below the soil surface. Mating and egg laying occur continuously for about two weeks with each female depositing 24 to 36 eggs. The average lifespan of the adult is about three weeks.

Managment: Adult chafers begin emerging in late May and early June at the time of grape bloom. A spray application is recommended if more than 2 beetles per vine are present. If only a few beetles are present , they may be handpicked from the vine and destroyed. The pupal stage is extremely sensitive to disturbance therefore, cultivating between rows may be effective in destroying a good number of chafers, however it is our experience that growers with sufficient numbers of beetles to inflict economic damage will not be able to control this pest by this method of cultural control.

An alternative method to chemical control has been developed by the department of Entomology at Ohio State University for this pest. This method utilizes a very powerful feeding attractant and a Japanese beetle trap. Intensive trapping over a 4 year period reduced the population to below the threshold level of two beetles per vine. An application of insecticide may required in combination with the trapping effort if the population is extremely high. It is our experience that it takes a couple years of intensive trapping to reduce the population within a heavily infested vineyard to the point that chemicals are no longer needed to control this pest.

Rose chafers can be handpicked and destroyed if the infestations are light. 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 2-3 weeks of heavy damage the beetle numbers appear to subside.