Corn Flea Beetle Sighting in Western Iowa

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Jackson Walsh, Legend Seeds Sales Intern

Recently, Mike Knight and I were evaluating a plot in northwestern Iowa. While doing a stand count, I discovered corn flea beetles on multiple plants. Although most damage done in these early stages is not too extensive, these beetles can transmit Stewart’s disease.

April Borders, Research & Agronomy Development Manager

Corn flea beetles are small, shiny black beetles that overwinter in grass close to corn fields. Adults emerge in the spring and feed on grassy weeds or winter wheat before moving over to corn. The beetles feed on the leaves by eating parallel to the leaf vein on both the upper and lower leaf surface. The feeding creates a windowpane effect and can cause the leaf to look bleached. The feeding scars are sometimes confused with beetle populations that can sometimes kill seedlings. As mentioned above, the corn flea beetles are vectors for a bacterial disease called Stewart’s disease. Because there is no chemical control for Stewart’s disease, the use of resistant hybrids is the key management strategy. The susceptibility of field corn (dent corn) is low to this disease. However, sweet corn can exhibit a high degree of susceptibility.


The best times to scout for these beetles is during the first three weeks after emergence and again during the early part of pollination. Pay special attention when scouting susceptible varieties. Look at 20 plants at five different locations within each field to determine the number of adults per plant, and then rate the feeding injury. The threshold for applying a foliar insecticide to field corn before V5 is five or more beetles per plant and 50% of plants show severe feeding. For sweet corn, the threshold is six or more beetles per 100 plants. Systemic seed treatments help provide early season control of the corn flea beetle. Also keeping fields and surrounding areas weed free will help to minimize overwintering adults.

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