Japanese Beetle Grubs

As the name rightly suggests, Japanese beetles are natives to Japan, but are now found in many parts of the world. In the United States, this beetle was found for the first time during 1916 and it is said that a consignment of iris bulbs from Japan contained Japanese beetle larvae that caused the spread of this pest in the country. Now, it is one of the most common garden pests that cause harm to most of the garden plants and lawn grass. Apart from the adult beetles that feed on the foliage of garden plants, Japanese beetle grubs are found to be more harmful, as they are voracious feeders of the roots of plants, especially, lawn grass.

What are Japanese Beetle Grubs

Japanese beetle (Popillia japonica) is a common and destructive pest in many countries including the United States. While, in Japan, it has various natural predators that control Japanese beetle population, in other parts, there are no such natural control measures to check their rising number. They are considered as serious pests for around 200 plant species. These plants include lawn grass, rose, canna, crape myrtle, grapes, etc. An average adult Japanese beetle has a body length of around half an inch and a width of almost ¼ inch. The elytra (the hardened forewings) of these beetles are copper-colored and the body has a greenish hue. On each side of their abdomen, six patches of white hair can be seen. Japanese beetle grubs are usually white in color with fine brown hair and short spines. These C-shaped grubs are almost two centimeters in length. They have slightly brown-colored head and a body with three pairs of legs.

Japanese beetle life cycle can be anywhere between one to two years. Each adult female Japanese beetle burrows into the soil and lays around 40 to 60 eggs during the onset of summer. Within two months, the eggs hatch and develop to grubs that feed on the roots of lawn grass voraciously till fall. From the fall to the next spring, these Japanese beetle grubs lay dormant. They emerge from dormancy during spring and continue to feed on the roots of lawn grass and other plants, until they transform to adult beetles, within a month or two. These adult beetles mate and get ready to lay eggs during the next summer.

Japanese Beetle Grub Control

As compared to the adult beetles, Japanese beetle grubs are more destructive, as they directly feed on the roots of plants. In order to control and kill these grubs, you must have a basic idea about their life cycle. Adult beetles emerge from the larvae during the onset of summer (June) and start feeding on the plants. These insects mate during this time and lay eggs, that hatch by mid summer and the grubs start feeding on the roots. They lay dormant from late fall to spring. Once they come out (during April), they continue feeding and transform to adults during the onset of summer (June). In short, the active period of Japanese beetle grubs are mid summer to late fall and from mid spring to early summer. During this period, you have to be extra careful and adopt every possible method to kill these grubs.

Milky Spore Bacterium: There are various methods to exterminate Japanese beetle grubs, but it's better to adopt natural methods, rather than using chemicals. Milky spore bacterium is one such method for the biological control of these grubs. This bacterium, which is available in the market, in powder form, has to be applied on the lawn and garden, as per the instructions of the manufacturer. The bacterium, when ingested by these grubs, cause milky spore disease in them. This results in the death of these grubs. You have to use this 'milky spore' continuously for around one to five years for eliminating Japanese beetle grubs.

Other Methods: While some people use pheromone traps for Japanese beetle control, others use soap water spray for killing Japanese beetle grubs. It is also noted that the grubs, when placed in soap solution, die soon. It is also said that plants like, garlic, chives, pancy, etc. can repel these beetles and grubs. You may also hand-pick these grubs and kill them. Use of insecticides and sprays can also help to some extent. You may also avoid growing plants that attract these beetles.

In short, Japanese beetle grubs can cause extensive damage to your lawn and garden, if they are in large numbers. So, take enough care to get rid of them, as soon as possible.