Metallic green or greenish bronze beetles, ranging from 1/3 to 5/8 inches long, have reddish wing covers and two prominent, and several smaller, white spots near the tip of the abdomen and along the sides. They feed on the husks, foliage, kernels and silk at the tip of the ear.
Japanese beetles pass the winter as grubs, about ½ to ¾ inch long, buried in the soil . Growth is completed during June, and the adults emerge in greatest numbers in July. The female beetles lay their white eggs 2 to 6 inches deep in the soil. The grubs feed mainly on decaying vegetation at first, but later on the fine roots of grasses and other plants. In high numbers, they can cause serious damage to lawns and golf greens. The grub resembles the common white grub but is only ¾ to 1 inch long, when full-grown, and can be distinguished from its near relatives by the appearance of the last ventral segment. The adults are common during July and August. The prefer to feed on parts of the plant exposed to the sun.
Biological: USDA imported and released about 49 species of natural enemies of the Japanese beetle. Only a few of these became established, the most widely distributed of which are the tiphiid wasp larval parasites (Tiphia vernalis and T. popilliavora) and the tachnid fly (Hyperecteina aldrichi). These parasitoids provide some suppression, but their occurrence is sporadic and they cannot be relied upon for control.
Cultural: Select sweet corn cultivars with good tip coverage.
Monitoring: Treat when necessary during silking, often treatments can be limited to outer boarder rows of large fields of sweet corn.
Chemical:Generally, Japanese beetles are controlled by sprays used to control corn earworm, European corn borer, and fall armyworm.
Ambush 2 E (permethrin)- Apply as a foliar treatment at 6.4 to 12.8 fl oz per acre to a limit of 76.7 fl oz per acre per season.
Asana XL (esfenvalerate)- Apply as a foliar treatment at 5.8 to 9.6 fl oz per acre to a limit of 96 fl oz per acre per season.
Baythroid 2 (cyfluthrin)- Apply as a foliar treatment at 0.8 to 1.6 fl oz per acre to a limit of 10 applications per season.
Diazinon 14 G (diazinon)- Apply as a foliar treatment at 7 to 14 lb per acre.
Malathion 57 EC (malathion)- Apply as a foliar treatment at 1-½ pt per acre.
Pounce 3.2 EC (permethrin)- Apply as a foliar treatment at 4 to 8 fl oz per acre to a limit of 48 fl oz per acre per season.
Sevin 80 WSP (carbaryl)- Apply as a foliar treatment at 1-1/4 to 2-½ lb per acre to a limit of 8 applications per acre per season. Allow at least 7 days between sprays.
Warrior 1 E (lambda-cyhalothrin)- Apply as a foliar treatment at 2.56 to 3.84 fl oz per acre per season to a limit of 3.84 pt per acre per season.