Issue No. 5, Article 3/April 22, 2005
Corn Flea Beetles Feeding on Seedling Corn
The warm winter indicated that corn flea beetle survival could be high in most areas of Illinois (issue no. 1, March 16, 2005, titled "Winter Temperatures Predict Promising Year for Corn Flea Beetles"). Duane Fredericking, Pioneer, has gotten several reports of high populations of corn flea beetles in central and west-central Illinois.
Flea beetles injure corn by feeding off the epidermis of leaves, resulting in small feeding streaks or windowpane feeding patches. Foliar feeding caused by the corn flea beetle rarely causes economic injury. High densities and severe feeding may result in skeletonization of the leaves and even death. Soil moisture is also an important factor. A few years ago when soil moisture was less than plentiful and corn flea beetles were abundant, the injury caused by flea beetles killed corn seedlings in western Illinois. The growing conditions did not enable the seedlings to recover from the injury.
Corn flea beetle adult (small, shiny, black, with enlarged hind legs).
Corn flea beetles causing sever injury to corn seedling.
Another threat of the corn flea beetle is its ability to transmit the bacteria Erwinia stewartii, which causes Stewart's wilt of corn. Two phases of Stewart's wilt will occur on corn. Most commercial corn hybrids are resistant to the seedling wilt phase of the disease, while many are somewhat susceptible to the leaf blight phase. On the other hand, many seed corn inbreds and sweet corn hybrids have varying susceptibility to Stewart's wilt.
We strongly encourage you to scout early-emerging corn for early-season insect pests such as corn flea beetles. Treatment for corn flea beetles on seedling corn may be warranted if you find five or more beetles per plant before the V5 stage of growth, especially if the plants are suffering from environmental stress (e.g., lack of sufficient moisture, slow growth due to cool temperatures). But don't overreact to the presence of flea beetles. Insecticides suggested for control of flea beetles in corn are presented in Table 2.