UPDATED: July 7, 2009
Check Your Fields!
Japanese Beetles have been clipping corn silks and feeding on soybean leaves.
By Ed Corrigan
The good news is that the grub stage of this species has, or soon will, stop feeding. The bad news of course is that the voracious beetle is beginning to emerge.
This year’s adults are the result of eggs that were laid by female beetles last summer. After these eggs hatched in mid to late summer, the grubs immediately began to feed on roots and decaying organic matter in the soil. They continued feeding until cold temperatures prompted them to move deeper in the soil profile to overwinter. Early this spring, the surviving grubs returned to near the soil surface to feed. Spring root-feeding by the grubs can result in serious damage to early-planted crops, especially corn. Though expected because of the cool, wet conditions this spring, we have heard of very few grub problems this year, which underscores the unpredictability of this insect.
Japanese beetles will feed on more than 350 different species of plants, but are especially fond of roses, grapes, smartweed, soybeans, corn silks, flowers of all kinds, and overripe fruit. Beetle damage to cultivated crops is often minimal and defoliation (leaf removal) on soybean usually looks much worse than it is. The beetles often congregate in several areas of a soybean field - often field borders - feeding on and mating in the upper canopy. The beetles’ iridescent, metallic color and their proximity to the field edge catches the attention of those doing “windshield” field inspections. Closer inspections will often reveal that weeds such as smartweed have made fields even more attractive to the beetles.