Considering this is the century mark for Popillia japonica in America (technically, it’s Popillia japonica Newman), let’s take a look at who and what this pest really is.
Starting with its debut in New Jersey, the Japanese beetle has become one of the most widespread and destructive pests of lawns and landscapes in the U.S. According to the USDA’s Animal and Plant Health Inspection Service (APHIS), nearly every state east of the Mississippi River (with the exception of Florida and Louisiana) is known to be “generally infested”; six more states, including (north to south) South Dakota, Nebraska, Kansas, Oklahoma, Texas and Mississippi, host partial infestations. The western half of the U.S. remains relatively free, although, as you read above, positive IDs have been made in Oregon, and many other Western states have reported outbreaks, if not established populations. After 100 years, it appears there’s not much that’ll stop this pest’s march across the continent.
Strikingly beautiful, if you’re into that sort of thing, the Japanese beetle adult has a bright, metallic green body that’s covered (not completely) by shimmering, copper- or bronze-colored wing covers. Five patches of white hairs appear on each side of the abdomen, and a similar pair of patches on the last abdominal segment helps to distinguish P. japonica from similar beetles.
This brilliance and its distinguishing marks make the beetle easy to spot, as does its size: Adults are about 1/3 to ½ inch long by about ¼ inch wide – about the size of a pinkie fingernail – rendering it visible on the leaves and flowers it loves to munch.
Before it emerges to dazzle and destroy, however, the larvae live underground and wreak havoc on roots and turf. Each creamy white grub appears somewhat translucent, and the body is covered with scattered brown hairs interspersed with short, blunt spines. The head is brownish yellow with strong, darker mandibles. At rest, it adopts the characteristic “C” shape.
Read more: Japanese Beetle Hits Portland
Most Japanese beetles complete their life cycle in one year, although those found in cooler climates may live an additional year. Most of this time is spent out of sight. Grubs remain underground for the first half of the year, pupating in late spring to early summer. Adults emerge in mid-summer and begin laying eggs while they feed on virtually anything green, and the new grubs dig underground to continue the destruction.
More than 300 species of plants are known to play host to P. japonica, some serving as primary and others as secondary hosts. An obvious meal-of-choice is the rose, with Malus, Prunus, Rubus and Ulmus offering sustenance as well. Secondary hosts include Aesculus, Althaea, Betula, Castanea, Hibiscus, Juglans nigra, Platanus, Populus, Salix and others serving lunch on a daily basis. When there’s an infestation, it’s safe to assume that few plants are immune from attack by Japanese beetles.
Both larvae and adults cause extensive damage, with larvae feeding on roots and causing untold damage to turf, while adults skeletonize leaves and destroy flower buds.
How to manage the beasts? If a population is (very) small, physical removal can be effective, especially in the cooler morning hours when the pests are less active. Pluck ’em and drown ’em in a bucket of soapy water, or snatch and stomp.
The use of attractants and traps remains somewhat controversial; they can be effective in luring insects, but that often has proved to backfire by, well, luring more pests to a planting.
Chemical control can be effective, and it’s best to check with state and local extension authorities to determine the best choice for your area. Biological controls show promise, but again, it’s a good idea to check with pest control professionals to determine the most effective and safest methods.
It’s not necessarily a losing battle, but it’s an ongoing one. Good scouting, optimal cultural practices and patience are key.
Read more: An Insect Pest Review/Preview