Late- season infections will show up as lesions on the leaf and possibly accelerate corn dry down. When plants are severely infected with the disease during the seedling stage, they will wilt, die, and dry up. If bacterial wilt is introduced by the pest's feeding, an irregular lesion can be seen beginning at one end of the flea beetle's feeding scar.
This feeding damage varies from that of the adult corn rootworm since they tend to eat out large areas along the margin of the leaf, leaving the epidermal layer. The feeding scar will run parallel to the leaf veins and sometimes zigzags across the vein into the next vein, giving the feeding scar a jagged appearance. In general, feeding on grasses (including corn) appears as very narrow areas where the green leaf tissue has been removed leaving a clear membrane (epidermis of leaf).
Damageįlea beetle damage symptoms vary between the type of hosts attacked. This damage typically occurs during the first few weeks after the young corn plants emerge. However, most damage to corn plants is done by the overwintering adults. Most species complete one or two generations during the growing season. The feeding and developmental characteristics of flea beetles are not well studied.
The larvae hatch and feed on the root systems of host plants. Eggs are deposited on plant leaves or in the soil around the root systems of host plants. In the spring, the adults migrate out of their overwintering site as soon as adequate vegetation is available for feeding and egg deposition. Adults reside in field rows, roadsides, and other protected areas to overwinter. Most flea beetle species overwinter in the adult stage. On rare occasions, root feeding by larvae can cause economic damage to corn. Some species' bodies tend to taper toward the head. Their body is milky white and cylindrical with a dark head capsule and three sets of legs, located immediately behind the head. In general, they look similar to the larvae of the corn rootworm, but have a more slender shape. The larvae vary in appearance depending on species. When approached or touched, the insect will jump off the plant in a similar fashion to a grasshopper. These hind legs give the insect its common name. The adult corn flea beetle is shiny black, very small (less than 1/16 inches long), and more or less rounded, with large hind legs for jumping. In general, sweet corn varieties tend to be much more susceptible to the disease. Therefore, most cornfields escape economic injury from the disease, although some hybrids are more susceptible to the disease than others. Injury to field corn caused by disease inoculation has been reduced in modern hybrids because of their moderate to high levels of resistance. It harbors the bacteria in its gut, providing a mechanism for the disease organism to survive the winter. The insect picks up the disease when feeding on diseased plants and then carries it to new hosts. Flea beetles are a concern in corn production because they can transmit Steward's disease (bacterial wilt).
Although the pest can kill young seedlings by causing significant defoliation, this level of injury is very rare. The pest is primarily a problem during the early growth period of corn seedlings (emergence to fourth leaf stage). A higher percentage of adults survive the winter under these conditions. The frequency of economic damage increases in years when average monthly temperatures for January, February, and March total 85 or more. The pest also attacks other field crops that are grown in the state, including soybeans, sorghum, small grains, sweet corn, and several vegetable crop species (particularly those in the nightshade and cabbage families).įlea beetles can be found feeding in cornfields throughout the summer, although few fields have economic infestations in a given year. Several other species can be seen, but they are seldom found in numbers high enough to cause significant injury to the crop. The corn flea beetle is the most common species found in Pennsylvania attacking field corn.
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