Japanese beetle adults are a common sight during the summer. They tend to gather in large numbers on shrubs and trees after emerging and can often be found congregating in balls of a hundred or more beetles on the turf. In a normal year, most of the adults emerge in July. Adults emerge between late June and the middle of August. The grubs move back up to the grass roots in April and begin to feed again. The grubs dig deeper into the soil to avoid the frost as temperatures drop in the fall. If adequate moisture is available from rain or irrigation, the grubs will molt to second and then third instars by mid- September. The larvae hatch about 10 days later and begin feeding on the grass roots. ![]() Eggs are laid in early July through September on turf. The larvae are white C-shaped grubs varying from 1/8 inch when newly hatched to about 1 inch when fully grown. There are five tufts of white hairs on both sides of the abdomen and a pair of tufts on the end of the abdomen. The thorax is green and wingcovers are metallic reddish brown. Japanese Beetle: adult and larvae Life historyĪdults are 3/8 to 1/2 inch long. If populations are high, they can remove all of the green leaf material from the plants. Adult beetles feed on the top of the leaf, eating the tissue between the veins, leaving the leaves skeletonized. The most favored include apples, cherries, grapes, peaches, plums, blueberries, asparagus, beets, broccoli, rhubarb, snap beans, sweet corn, soybeans, birch, crabapples, hollyhocks, linden, maples, mountain ash, roses and sassafras. The adults emerge in early July and feed on the leaves of nearly 300 species of susceptible plants. ![]() They can tear up large patches of turf as they dig for the grubs. A secondary concern is skunks, raccoons, crows and geese feeding on the grubs. Damage becomes evident during droughty periods and is typically observed in the fall if larval numbers are high. The larvae prune off the roots, causing the turf to have difficulty maintaining water uptake. Japanese beetle grubs are actively feeding on grass roots from April to the end of May and from August to November. Grub damaged areas usually appear in the fall. Sod, soil or nursery stock must be certified as free of Japanese beetle if it is going to be shipped to states without Japanese beetle. Japanese beetle is also a quarantine concern to commercial growers. If the local population is high enough, the most susceptible hosts, such as lindens and roses, can be completely defoliated. The adults are voracious feeders that damage a wide variety of ornamental shrubs and trees. However, with frequent rain in July and August, the adults will readily lay eggs in non-irrigated turf. It normally is not a problem of non-irrigated turf. Japanese beetle larvae can cause serious damage to golf course fairways and occasionally to home lawns. It has recently been found in Traverse City and a few other sites in the northern Lower Peninsula. Japanese beetle can be found in most locations south of a line from Muskegon to Bay City. Individual beetles were collected in Michigan in the 1930s, although the insect did not become established in the Detroit area until the early 1970s. Since then, it has gradually spread westward and has been reported in every state east of the Mississippi River. ![]() It was first found in the United States in New Jersey in 1916. The Japanese beetle, Popillia japonica Newman, is a native of Japan. You can download an excellent Cornell University Factsheet. and that milky spore will not control them? Is anyone knowledgeable enough to identify the Japanese beetle grubs and monitor their population decline? Are you SURE the milky spore product contains live bacteria? (There was a scandal a few years back when one company was shown to be shipping dead spores in their product.) Fall is the right time to apply milky spore powder – but be sure everyone understands what their contribution to the campaign will and won’t accomplish. Your group should first ask these questions: Will people be satisfied with a “cure” that takes years to become fully effective? Are they aware that several other beetles make white grubs in the soil…. This approach, though, is not a magic bullet. Otherwise, lawns that were not treated could harbor beetles that would affect the rest of the neighborhood. Your neighbor is on the right track when he advocates a community-wide program. What are your thoughts? Does it have any merit?Ī: Milky spore disease kills the grubs of Japanese beetles once it infects the soil in which the beetles lay their eggs. There are 500+ homes in our subdivision and it will cost $100 per home. One of the people in our subdivision is encouraging us to have a community-wide eradication program using milky spore disease powder. Q: Japanese beetles are a big problem for us.
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