'' (white) on a Japanese beetle: The fly was introduced from Japan for
biocontrol.
Phenological models might be useful in predicting the timing of the presence of larvae or adults of the Japanese beetle. Model outputs can be used to support the timely implementation of monitoring and control actions against the pest, thus reducing its potential impact. Owing to their destructive nature, traps have been invented specifically to target Japanese beetles. These comprise a pair of crossed walls with a bag or plastic container underneath and are baited with floral scent,
pheromone, or both. However, studies conducted at the
University of Kentucky and
Eastern Illinois University suggest beetles attracted to traps frequently do not end up in the traps; instead, they land on plants in the vicinity and cause more damage along the flight path and near the trap than may have occurred if the trap were not present. During the larval stage, the Japanese beetle lives in
lawns and other
grasslands, where it eats the roots of
grasses. During that stage, it is susceptible to a fatal disease called milky spore disease, caused by a bacterium called
milky spore,
Paenibacillus (formerly
Bacillus)
popilliae. The
USDA developed this biological control, and it is commercially available in powder form for application to lawn areas. Standard applications (low density across a broad area) take from two to four years to establish maximal protection against larval survival, expanding through the soil through repeated rounds of infection. Control programs based on milky spore disease have been found to work most efficiently when applied as large-scale treatment programs, rather than by isolated landowners.
Bacillus thuringiensis is also used to control Japanese beetle populations in the same manner. Research performed by many US extension service branches has shown that
pheromone traps attract more beetles than they catch; under favorable conditions, only up to three-quarters of the insects attracted to a trap are captured by it. Traps are most effective when spread out over an entire community and downwind and at the borders (i.e., as far away as possible, particularly upwind) of managed property containing plants being protected. When present in small numbers, the beetles may be manually controlled using a soap-water spray mixture, shaking a plant in the morning hours and disposing of the fallen beetles, Several insect predators and
parasitoids have been introduced to the United States for
biocontrol. Two of them, the fly
Istocheta aldrichi, a parasite of adult beetles, and the solitary wasp
Tiphia vernalis, a parasite of larvae, are well established with significant but variable rates of parasitism.
T. vernalis reproduces by locating beetle grubs through digging, and on finding one, paralyzing it with a sting and laying an egg on it; on hatching, the wasp larva consumes the grub.
I. aldrichi, instead, seeks out adult female beetles and lays eggs on their thoraces, allowing its larvae to burrow into the insect's body and kill it in this manner. A female
I. aldrichi can lay up to 100 eggs over two weeks, and the rapidity with which its larvae kill their hosts allows the use of these flies to suppress beetle populations before they can themselves reproduce. Soil-dwelling
entomopathogenic nematodes are known to seek out and prey on Japanese beetle grubs during the subterranean portion of their lifecycle by entering larvae and reproducing within their bodies. Varieties that have seen commercial use as pest-control agents include
Steinernema glaseri and
Heterorhabditis bacteriophora. Initially discovered in 1987,
O. popilliae has been observed inhabiting the
malpighian tubules of third-instar larvae. This leads to swelling, inefficiency in the gut, and potentially cause
microsporidiosis in the infected beetles. This infection weakens the beetle and creates a suitable breeding ground for
opportunistic pathogens. == Host plants ==