Corn flea beetles are very small black insects with incredible jumping abilities. Direct feeding is generally not a concern unless seedlings are small and under environmental stress, and a great number of beetles are feeding. A larger concern is the potential transmission of the bacterium that causes Stewart’s bacterial wilt.
The tiny (about 1/16 inch in length) black overwintering adults can be seen feeding on seedling corn soon after emergence (Figure 1, top). The insect has the ability to jump considerable distances when disturbed. Therefore, one must be cautious when looking for them as they can jump quickly to the soil or another plant.
Corn flea beetles feed by removing the leaf’s photosynthetic energy producing top layer. The damage appears as grayish or brownish lines.
Economic damage by direct feeding is generally not a concern. Under favorable growing conditions, seedling growth can outpace their feeding. However, under high beetle populations and cold and wet growing conditions, the beetles can overtake the seedlings.
The larger concern from their feeding is the transmission of the bacterium that causes Stewart’s bacterial wilt (Figure 1, bottom). A number of seed products have resistance or very good tolerance to Stewart’s bacterial wilt. Products without the resistance or tolerance can wilt and die from the disease. Seed treatments with insecticidal properties and soil applied insecticides at planting can help manage flea beetles.
If flea beetles are found during a routine visit to the field, more in-depth scouting and evaluation should be undertaken. Randomly select 20 consecutive plants in 5 areas of the field. Observe the top and bottom sides of leaves for the beetles. Record the number of damaged plants, the severity of the damage, and the number of beetles present. Controls may be necessary if seedlings have less than 4 collared leaves (V4 growth stage), 50% of the seedlings show severe feeding, there are populations of 5 or more beetles/plant, and growing conditions are poor.
Mild winters favor the survival of the adults. If the sum of the mean daily temperatures for December, January, and February total above 90, survival can be moderate to high (above 100).
Corn flea beetles. Field Crops IPM. Purdue University. https://extension.entm.purdue.edu/fieldcropsipm/corn.php.
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