Order:
Family:
Scarabaeidae
Species:
Maladera castanea (Arrow)
Size:
The adult beetle is 5/16 to 7/16 of an inch long (slightly smaller than a Japanese beetle adult). A fully developed grub (third instar) measures about 3/4 inch long
Colour:
The adult is chestnut brown or reddish brown in colour and faintly iridescent. The grub (immature stage) is off white except for a distinct head capsule and three pairs of true legs that vary from in colour from orange to dark brown.
Description:
The beetle abdomen is covered by a pair of hardened forewings, or elytra, which are not used in flight. Instead, their main purpose is to protect the hind wings, which are folded up under the elytra when the insect is not in flight.
The grub has a distinct head capsule and three pairs of true legs and will fold into a ‘C’ shape when disturbed. It is very easy to differentiate an Asiatic garden beetle grub from other annual white grub species with the aid of a 10x power hand lens.
The grub has a single transverse row of spines on the underside of the last abdominal segment, or raster, and a ‘Y’ shaped anal slit.
Range:
The Asiatic garden beetle is native to Japan and China and was first introduced into the United States in the 1920s. It commonly occurs throughout the north- eastern part of the country, from New England to as far south as South Carolina.
Habitat:
The Asiatic garden beetle is known to feed on more than 100 plant species, with some of the more important hosts including fruits, vegetables, flowering plants, weeds, and grasses.
Life Cycle:
The life cycle of the Asiatic garden beetle is similar to other annual white grub species with four distinct life stages, egg, larva (or grub), pupa, and adult. Adult beetles are present from late June to late October, but are most abundant from mid-July to mid- August. Adults are nocturnal and feed only at night.
During the day, adults can be found just below the soil surface near favored host plants. After feeding for several nights, the female mates and begins laying eggs in small clutches over a period of several weeks.
A clutch may contain up to 20 eggs, and a single female will deposit anywhere from three to 15 clutches in the soil at depths of 1 to 2 inches depending on soil type and moisture. Eggs begin hatching about two weeks after being laid, usually from late July to early August.
Newly hatched grubs (first instar) feed on roots and decaying organic matter and molt to the second instar stage in September. Many second instar grubs do not reach the third instar stage until the following spring.
Asiatic garden beetle grubs have been reported to overwinter at soil depths of 8 to 17 inches depending on soil type; however, for most soils in Virginia, the grubs usually overwinter within the top 4 to 6 inches. The following spring, overwintering second and third instar grubs return to just beneath the soil surface and feed for several weeks.
When immature development is complete, pupation occurs in earthen cells at depths of up to 6 inches. The pupal stage lasts from eight to 15 days and adults emerge shortly thereafter. Adult emergence usually occurs when nighttime temperatures exceed 70°F, typically in late June.
Type of Damage:
The grub injures seeds and newly developing roots of corn seedlings in a manner similar to other annual white grub species. They are typically more common in loamy to sandy loam soils compared to heavier soil types.
On germinating corn seeds and seedlings, the grubs will chew off the fine rootlets, interfering with the uptake of water and nutrients, especially phosphorus. Severe injury results in unthrifty or dead seedlings, which in turn, results in a poor crop stand.
Feeding injury by adults on leaves and other above ground parts of corn is not considered of economic importance. However, adult feeding can cause serious injury on certain turfgrass species and other host plants.
Typical injury to turfgrass by Asiatic garden beetle adults results in irregular holes toward the margin of leaves, and severe injury leading to complete defoliation with the exception of the midrib.
Information Sourced From:
