Japanese beetles are back

It is that time of year when Japanese beetles can be seen feeding on our plants, bushes, and trees in the landscape. Japanese beetles are an invasive species brought over from Asia. They were first noticed in North America in 1916 in a nursery in the Philadelphia area. As an invasive species they had no natural biological controls to keep their populations in check. Japanese beetles are found in all states east of the Mississippi River and they continue to gradually move westward. There is one life cycle per year for the Japanese beetle. The adult beetles emerge from the soil in late June into July. The adults live for about 60 days. This is the feeding and mating stage in their life cycle. The adults feed on over 300 species of plants. They begin feeding on the tops of leaves and work their way down the leaves leaving a skeletonized appearance. Odors from the beetle-damaged leaves attract other beetles. Adult beetles also produce a pheromone that further attracts more beetles to congregate. In the evening around dusk, the female will fly to turf areas to deposit her eggs. The female will burrow three inches into the soil and deposit her eggs. A female produces between 40 to 60 eggs in a season. The eggs hatch in about 10 days and the small grubs (1/8 inch long) begin feeding on grass roots. In late July into September, the grubs will feed on the roots of grasses. They will grow to around one inch. As the soil temperature cools to around 50 degrees, the grubs will burrow 6 to 12 inches into the soil to over winter. In April into May when the soil temperature reaches 50 degrees the grubs will emerge to begin feeding on grass roots. The grubs will pupate between mid-May and the beginning of June. In this stage they stop feeding before maturing into adults. Understanding the Japanese beetle life cycle is important in the choice and timing of control methods and effectiveness of the control applied. The choice of control method is a personal one, depending on your tolerance for insects and plant damage. Control methods include preventive, insecticides, chemical controls for grubs and biological controls such as parasites, nematodes and fungi. A preventive control strategy should be the first approach. Maintaining healthy plants through proper fertilization, removing weak and diseased plants, irrigation especially during dry periods, and frequent mowing at a height of 3 inches along with limited use of pesticides to maintain a healthy mix of beneficial insects in the lawn. If you notice Japanese beetles feeding in an area it does not mean you have a grub infestation. On the other hand, hanging a Japanese beetle trap almost guarantees a highly localized population. The traps use floral and synthetic sex pheromone scents that attract beetles. You will catch beetles and have more feeding on your plants. Controlling adult beetles: If you have only a few, hand pick them or shake them off the plant into a jar with soapy water. When applying insecticides, spray the leaves and flowers thoroughly. Repeat the application, as necessary. Read the labeling information carefully and follow the instructions. For food crops, pay attention to the minimum number of days that must be observed between application date and harvest date. Controlling grubs: There are two types of chemicals that can be used for controlling grubs: curative products and preventative products. Read the labeling information carefully and follow the instructions. Curative products are used to kill actively feeding grubs now and have a grub reduction efficacy rate of 40% to 60%. Preventative products take one to two weeks for the chemicals to be taken up by the plant and reach where the grubs are feeding. These products are most effective on small grubs. The efficacy rate can be as high as 90%. The best time to apply is in August and September when the soil temperature is above 60 degrees and grubs are actively feeding on the grassroots. Biological controls: There are effective biologic controls. Nematodes — microscopic parasitic roundworms actively seek out grubs. These nematodes have a symbiotic relationship with a specific species of bacteria. The nematodes inoculate the grub with bacteria that quickly spreads feeding on the grub. The nematodes in turn feed upon the bacteria killing the grub. Parasites have been introduced from Asia to control Japanese beetles. Tiphia Vernalis, a small wasp burrows into the ground and find grubs to slay its eggs within to become a host, eventually killing the grub. Istocheta Aldrichi, a solitary fly that deposits its eggs on the thorax of the adult beetle. The maggots bore into the beetle cavity killing the beetle. The Japanese beetle is here to stay. It can be a destructive pest of trees, plants and turf if left unchecked. By using an integrated pest management strategy, the homeowner can effectively manage the Japanese beetle population in the landscapes.