Japanese beetles are the most widespread turf and grass pests in the United States. Native to Japan, these bugs were first discovered in the United States in 1916 in Riverton, New Jersey. With no natural predators on this continent, these beetles have been slowly spreading across the country over the past few decades.
Meet the Beetles
Adult Japanese beetles eat more than 400 plant varieties. They lay eggs up to four times a year in moist turf, like freshly watered grass, and around plants, particularly trees. The eggs hatch in August and the grubs feed off plant roots, causing patches of dead grass.
Signs of Japanese beetle infestation include devoured plants and dead patches of grass. To find out if they are present in your lawn, pull the grass back. If you have them, you will see grubs, which grow from ½" to 1" long, eating the roots. If you don't see beetles or dead grass but you have a sickly plant in your yard, you can dig carefully around the roots of an afflicted plant to look for grubs.
Ways to Stop Them
An environmentally conscious way to get rid of Japanese beetles is to hand-collect and destroy them. Although it sounds ineffective, the collecting does slow the damage. The presence of even one beetle can attract others, since Japanese beetles can fly anywhere from one to five miles to look for food, mates and a suitable place to lay eggs. This is why pheromone traps, sold at gardening shops to get rid of Japanese beetles, are more harmful than effective and can actually attract more beetles to your garden.
Pesticides, particularly those that specifically target grubs, can prevent the beetles from destroying your plants. The availability of particular pesticides effective against Japanese beetles depends on the state you live in, so it's best to consult a local garden shop on which ones to use.
Pesticides, however, only protect your garden for the season. In recent years, an organic control method, Milky Spore disease, has become more popular with gardeners for fighting Japanese beetles. When applied to the ground, this powdery bacterium is ingested by the grubs. It multiplies until it kills the grubs. On their demise, more Milky Spore bacteria are redistributed in the soil for other grubs to eat.
Because Milky Spore continually regenerates as it destroys Japanese beetle grubs, it can last for 3 to 10 years. It is also safe to use around children and pets and is non-toxic to the environment. You can buy the powder in canisters in most specialty gardening shops. Although the bacteria can be a bit pricey, Milky Spore is a worthwhile investment.
As with most situations in a garden, the best defense is to plan for the next season. If you realize you have the beetles, you can apply a pesticide to your plants and yard to keep the bugs from eating and laying eggs. In late July and early August, spread Milky Spore on the yard following the directions on the canister. Milky Spore can even be used in conjunction with pesticides and fertilizers. If you have C-shaped patches, you may even want to pull up the turf and sprinkle the bacteria directly on and around the grubs. You can also reapply Milky Spore in the spring to destroy grubs that may have withstood the winter.
If you live in a neighborhood association or have close neighbors, you may want to talk to them about Japanese beetles as well. While the beetles may be repelled by your yard, it won't stop them from laying eggs close by.
Japanese beetles can do a devastating amount of damage to the leaves of fruit trees, bushes, vegetables, and a number of other outdoor trees, flowers, and plants. They feast on the tender parts of foliage, and they leave behind a path of destruction.
Every gardener, at one time or another, has had to deal with an infestation of some sort. I myself am something of a gardening novice, but my mother-in-law qualifies as an expert in my opinion. I recently sat down with her and went over various remedies and preventatives.
Japanese Beetles (Popillia japonica Newman) are a non-native invasive pest that is found in every state east of the Mississippi River. Arriving in the US on imported plants from Japan in 1916, the Japanese beetle has no natural enemies in the United States.