About the Corn Flea Beetle
Reproduction and Life Cycle
The corn flea beetle will overwinter as an adult, most often in leaf and plant debris or in the soil along fences and roadsides. When temperatures warm up to about 65 degrees Fahrenheit, the adults will emerge from the ground and will begin eating corn and grasses. Shortly after, they will mate and lay their eggs either at a plants base by the stem, in the ground by plant roots, or on plant leaves. The larvae will hatch after 10 days and will immediately begin eating plant roots and stems. They develop through 3 instars in about 3 to 4 weeks and then pupate in the ground. This stage will last anywhere between 7 and 10 days when the adult beetle will emerge. The corn flea beetle has approximately 3 generations annually. The last generation of adults would emerge in the beginning of August, feed, and then overwinter in the fall.
Corn Flea Beetle Identification and Habitat
The corn flea beetle is a shiny black beetle that is very small, less than 2mm in length. They have long hind legs and are known to jump far lengths. The eggs are white, about 0.35mm in length with a pointy end. The egg will darken slightly in colour before it hatches. The larvae are slimly shaped, white, and cylindrical. They can grow to be almost 9mm in length when it has fully matured through its instars. They usually have a darkened head. The pupa is also white and has the shape of an adult but is soft in texture; it will also darken as it completes this stage of development.
Corn flea beetles are most commonly found on corn plants east of the Rocky Mountains and will eat leaf tissue, resulting in corn leaves with noticeable scratch marks on the surface parallel to the leaf veins. While corn is the flea beetles preferred source of food, they are also found on a number of different grass types, oats, Timothy, barley and wheat. The adult causes the most damage, often transferring pathogenic bacteria called Erwinia stewartii to remove the plant tissue. This bacterium can lead to Stewart’s wilt, which some corn varieties are prone to. These bacteria will clog the plants vascular system, which hinders the plants nutrient movement and can lead to infection with vulnerable plant varieties, such as sweet corn hybrids. When the beetle is low in population, these scratches will not be detrimental to the plants health; however, if there are many beetles per plant, this will severely injure the leaves, giving it a white or silvery appearance. Signs of infestation in a corn field will not appear until later in the summer. Note that drought can encourage damage. Plants are also more likely to show signs of damage if they were fed on in its earlier stages of development. Usually the plants that were infected become stunted and will wilt. Mild winters are preferred by this beetle and increase their survival rate.
Corn Flea Beetle Management and Control Methods
If you are looking to avoid chemical control methods, there are a few techniques used that have been found to be effective at minimizing the corn flea beetle population. Plan to plow crop excess that remains in your fields and keep weed levels low in and around fields to deter the beetle from using them as their overwintering site. Additionally, using hybrid varieties that are wilt resistant will keep the yield loss from bacteria to a minimum. A winter with temperatures below freezing can also effectively control the corn flea beetle population.
If you are looking to use a chemical control method, insecticides for seed treatments and also foliar insecticides can be effective. These will give you the control that you need early in the season. Active insecticide ingredients for the corn flea beetle include alpha-cypermethrin, beta-cyfluthrin, bifenthrin, carbaryl, chlorpyrifos, cyfluthrin, and deltamethrin. It is advised to only use insecticides if there are more than 5 beetles on an individual plant, or if 50% or more of the seedlings have been badly damaged and if the plants are under stress from excessive heat or drought. Be sure to carefully read the label for cautions and proper application. It is extremely important to never spray on days that are windy.
Latin / Alternative Corn Flea Beetle Names