Japanese Beetles

From BASF: The Chemical Company Website

They’re back. Growers in the eastern half of the United States are regrettably familiar with Japanese beetles (Popillia japonica). Japanese beetles can be very problematic for many nurseries as they can quickly devour plant foliage and render crops not marketable. As the adults emerge from mid June thru early August, there seems to be an endless supply of these voracious feeders which consume a wide array of herbaceous and woody ornamentals. 

Adult beetles have an oval form measuring 0.375 inch (10 mm) long by 0.25 inch (7 mm) wide. They have a metallic green appearance with coppery brown wing covers. Other key identifiers are the clubbed antennae, two patches of short white hairs on its rear, and the five white hair tufts along each side of the dorsal abdomen. The adults are skeletonizers, feeding on the leaf tissue between the veins, leaving the veins behind. The injured leaves appear lace-like and often wither and die in the days ahead. On some plants, Japanese beetles do not skeletonize the leaves; the leaves and flower petals may appear to have holes in them or be consumed altogether.

The larval stages can be found under turf in the top 2 to 6 inches (5 to 15 cm) of soil. They are rarely observed feeding in the root zone of containerized plants. The larvae are easily identified and are most commonly referred to as the typical white grub measuring about 1.25 inches (32mm) long (the last 3 instars). They are c-shaped and have six legs.  Another distinguishing characteristic is the distinctive V-shaped pattern (rastral pattern) of the hairs on hind end of the abdomen. The eggs are laid beneath the soil surface from in July and August and do not emerge as adults until the following summer.

Controlling these insects is very difficult as the most effective control strategies involve controlling the larval stages. This may not be possible for many nurseries; however, it may be beneficial to treat crops that are growing in the ground, the sod within the production area, or the soil in adjacent fields to reduce the number of adults that might enter the production site in the future. Larvae control methods include applying Bacillus popilliae (milky spore disease) carbaryl, chlorpyrifos, diazinon, halofenozide, imidacloprid, lambda-cyhalothrin, permethrin, and trichlorfon. Treatments usually occur in the fall; applications may need to be reapplied as many of these products are rather short lived. No control strategy will eliminate the larvae altogether, but should effectively reduce the population by 50 to 90%.

The adults can be difficult to control since new adults may fly into the treated areas and re-infest the crops. Pheromone traps are highly effective at attracting beetles from over 0.25 mile (0.402 km) away. These traps should not be placed in the production area as they attract far more beetles than they can capture. There are several chemicals including bifenthrin, carbaryl, chlorpyrifos, cyfluthrin, deltamethrin, malathion, and permethrin that can control the adults with contact sprays. Repeated applications are usually necessary because some of these pesticides have relatively short residual effects and new adults may enter the production site following the initial application.

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