Another New Pest
Cotinis nitida (Linnaeus), are members of the order Coleoptera (beetles) and are not bugs. Beetles have hardened front wings that are called elytra, chewing mouthparts, and complete metamorphosis (egg, larva, pupa, and adult). In contrast, bugs have front wings that are half membranous and half hardened at the base (hemelytron) or completely membranous, sucking mouthparts, and incomplete metamorphosis (egg, nymph, and adult). This beetle is native to the United States and is found in an area bounded by Texas, Florida, New York, and Nebraska. It is a white grub, and the adults of white grubs are called May beetles of June beetles.
Adult green June beetles may be confused with adult Japanese beetles. The Japanese beetle is a serious pest that may become introduced in Louisiana. It is important to know if the Japanese beetle is found in Louisiana. Thus, it is important to be able to tell green June beetles from Japanese beetles.
Adult Japanese beetles are 3/8 to 1/2 inch long. The thorax is green and the front wings are metallic reddish brown. Adult Japanese beetles have five tufts of white hairs on each side of the abdomen. Additionally, there is a pair of white tufts of hairs on the end of the abdomen. The head and legs are black.
Adult green beetles are 0.5 inches wide and 1-inch long. The underside of the adult is metallic green and has orangish yellow areas. The edges of the shield behind the head (pronotum) and front wings are brownish yellow and, the top of the front wings are velvety green. The head and legs are mostly metallic green.
Green June beetles are larger than Japanese beetles. The tops of the front wings or wing covers of green June beetles are green while, those of the Japanese beetle are metallic reddish brown. Additionally, Japanese beetles have the white tufts of hairs, and a black head and legs. If adult Japanese beetles are found in Louisiana, collect the beetles and send them to Dr. Dennis Ring, Dept. of Entomology, 404 Life Sciences Building, Baton Rouge, Louisiana 70803.
The eggs of green June beetles are oval in shape and gray in color. The larvae are up to 2 inches long in length, have true legs, have a dark brow head and a C- shaped body that is creamy white. The larvae will coil up tightly if disturbed.
Eggs are oviposited in soil with decaying plant matter. Larvae hatch from the eggs in about 2 weeks and feed on manure, roots, decaying plants and humus. Newly emerged larvae are 3/8 inch long. Larvae feed near the soil surface at night and move deeper in the soil during the day. They overwinter in the soil at depths up to a foot or deeper. The larvae move close to the surface of the soil in the spring when temperatures reach 60 degrees F. Pupation occurs in May in earthen cells at a depth of 2 to 6 inches. The pupal stage lasts for 2 to 3 weeks, and adults remain in the cell in the soil for 1 to 2 week. Adult emergence occurs in June, July, or August and these beetles have one generation per year. Adults emerge following rains that soften the soil. Female beetles release sex pheromone from mid-morning to mid-afternoon. Males fly at waist height in a zigzag pattern searching for females. After mating, females fly close to the surface searching for moist areas with high organic matter (decomposed hay or decomposed manure piles). The female green June beetle digs 5 inches deep in the soil to build a walnut-sized ball of soil and lays 10 to 30 eggs in the ball. At oviposition, eggs are oblong. If there is enough moisture, eggs will increase in size becoming round and twice their original size. Females may lay up to 100 eggs.
Larvae feed on roots of ornamental plants, turfgrass, vegetables, corn, sorghum, oats, and alfalfa. One different characteristic of the larva is that it crawls on its back when moving on the soil surface. Adult green June beetles eat the leaves of many trees and shrubs and occasionally will attack berries and tree fruits. Adults will also feed on over-ripe fruit, and may be attracted to fruit baits. Soil amendments with high organic matter amendments and manures encourage infestations of green June beetles.
Traps are only effective for monitoring first adult emergence. Monitoring of adults may be accomplished by jarring several branches of trees, and counting the number of beetles flying off.
Parasitic nematodes (Steinernema and Heterorhabditis species) can decrease numbers of white grubs. Treatments using S. carpocapsae have shown less than 50% control, while treatments using H. heliothidis have shown 80% control in the Midwest. Nematodes and imidacloprid may work synergistically.
Insecticides for green June beetles include carbaryl (Sevin®), chlorantraniliprole (Acelepryn®), clothianidin (Arena®), imidacloprid (Merit®, Season-Long Grub Control®), halofenozide (Mach2®), Ortho Grub-B-Gon®), thiamethoxam (Meridian®), and trichlorfon (Dylox®). Green June beetle larvae will die on top of the soil rotting and making a mess.
Managing adult green June beetles is difficult because new beetles fly in daily. However, applications for adult green June beetles may be needed when large numbers of beetles are feeding on foliage. Irrigation right after treatment of the soil or treatment right after rainfall is important in managing larvae.
Image 1. Adult Japanese beetle, Pest and Diseases Image Library, Bugwood.org
Image 2. Adult green June beetle, Natasha Wright, Florida Department of Agriculture and Consumer Services, Bugwood.org
Image 3. Green June beetle larva, Clemson University – USDA Cooperative Extension Slide Series, Bugwood.org
Image 4. Green June beetle pupa and pupal cell, Jim Baker, North Carolina State University, Bugwood.org