![]() The four o’clock, also called marvel-of-Peru ( Mirabilis jalapa), has been reported by some gardening sites and blogs to not only halt the beetle’s garden invasion but kill them in the process. Is the four o’clock flower toxic to Japanese beetles? Although both natural enemies became established here, neither is very abundant and they have little impact on Japanese beetle populations. The fly Istocheta aldrichi lays eggs on adult Japanese beetles in summer, whereas the wasp Tiphia vernalis parasitizes grubs in the spring. Two natural enemies of Japanese beetles have been released in Minnesota. arborvitae, spruce, fir, pine), daylily, geranium, ginkgo, Japanese tree lilac, forsythia, common lilac, magnolia, red and silver maple, oak, white poplar, redbud, rhododendron and yew. Plants usually not damaged by Japanese beetles include boxwood, clematis, chrysanthemum, conifers (e.g. When choosing new plants for your landscape, consider using a less preferred plant. Using less preferred plantsĪlthough Japanese beetles feed on many different kinds of plants, there are some that they seldom damage. They attract more beetles than they catch. This usually results in more damage to nearby gardens and landscape plants than would have happened if no traps were present.ĭon't use Japanese beetle traps. ![]() While these traps can collect an impressive number of beetles, research at the University of Kentucky has demonstrated that more beetles fly toward the traps than are caught. They were developed by researchers to monitor for the presence of Japanese beetles so that management strategies could be implemented. The traps attract beetles using synthetic female sex pheromone and a blend of chemicals with a strong floral odor. And they may attract more insects to your yard. Hanging a trap in a home garden is not an effective way to protect plants. Instead, handpick beetles until the plant is done blooming and starting to set fruit, then cover it. fruits) as this will prevent pollinators from reaching them. However, do not cover plants in bloom that require pollination (i.e. In some cases, it is possible to protect plants with fine netting to prevent beetle damage. Netting can help keep Japanese beetles off plants Physical barriers As the soil starts to cool in the fall, the nearly mature, full-sized (third instar) grubs dig deeper in the soil, where they spend the winter.Grubs go through three different growth stages (instars) during the summer becoming progressively larger with each stage.The eggs hatch in about two weeks and the grubs feed mainly on the roots of lawn grasses.Dry soil conditions can reduce egg survival, resulting in fewer adult beetles the following year.Females will lay eggs several different times during July and August, totaling as many as 60 eggs.After mating, females tunnel underground in the soil one to three inches to lay eggs.Virgin females produce a sex pheromone for mating that is highly attractive to males.This often results in large clusters of beetles feeding and mating on particular plants while neighboring, equally attractive plants are only lightly infested.Beetle-damaged leaves emit feeding-induced odors that attract other beetles (like sharks to blood).Adults feed primarily in July and August, although some may be active into September.They can fly up to several miles to feed. Adult beetles start to emerge from the ground in late June or early July.In spring, grubs move up near the soil surface to finish feeding and pupate into adult beetles.Japanese beetle grubs spend the winter underground in the soil of lawns, pastures, and other grassy areas.The sides of the abdomen have five white patches of hair, and the tip of the abdomen has two patches of white hair.Metallic green head and thorax (the area behind the head) with copper-brown wing covers.The MDA maintains an updated distribution map of Japanese beetles. Japanese beetles are most commonly found in the Twin Cities metropolitan area as well as southeast Minnesota. ![]() By 2001, they occurred in much higher numbers. In one year the Minnesota Department of Agriculture (MDA) trapped more than one million beetles. Since then, Japanese beetle numbers have fluctuated from year to year. Japanese beetles were first discovered in Minnesota in 1968. It is now found throughout the eastern U.S., except for Florida, and continues to move westward. This pest is considered to be an invasive species. Until that time, this insect was restricted to Japan where it is not a major pest. Japanese beetles ( Popillia japonica) were first found in the United States in 1916, after being accidentally introduced into New Jersey.
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