Reports of flea beetle feeding on corn in certain parts of the country have come in over the past 10 days. This is an early season pest that doesn't become economic under most circumstances. That means that under most circumstances it does not pay to treat and kill this early season pest. However, it always pays to scout and know what's in your field. Otherwise, the insects and diseases are making decisions for you, instead of you making the decision as to whether or not there is anything you can do about them, and if there is, is there a possible payoff for doing it.
Dave Nanda, a plant breeder, crops consultant and director of agronomy and technology for Seed Consultants, Inc., says that the problem with the flea beetle is that it can carry a disease which can be more harmful to the corn later in the season than the feeding done by the insect itself earlier in the season. The pathogens that cause Stewart's wilt in corn overwinter in the gut of the flea beetle. And flea beetles are better likely to survive when the average monthly temperature for December, January and February add up to 90 degrees. That makes this a year worth watching for flea beetles.
Beetles are very small. They eat the green tissue on leaves, and can leave scars on a leaf if lots of them feed in the same place. Stewart's wilt often originates from these scars later in the season. These lesions are usually pale-green in the beginning, and alter become brownish and wavy. Stewart's wilt is a venerable foliar disease in corn because the damage can extend along the total leaf.
Sweet corn and seed corn inbreds are usually more susceptible. The problem is usually handled in commercial dent corn by picking hybrids that aren't susceptible. You may not see the symptoms in sweet corn until after tasseling, and it may appear as wilting leaves. You can control flea beetles in sensitive crops if you catch them early in the season.