Field Guide     Pest Management     European Corn Borer

European Corn Borer

CROPS IMPACTED: Corn, lima and snap beans, aster, buckwheat, cosmos, dahlia, gladiolus, hollyhock, hop, millet, oat, peppers, potatoes, soybean, and zinnia

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Family: Pyralidae

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About European Corn Borers

Reproduction and Life Cycle

The amount of reproduction is greatly dependent on the area in which European corn borers are living. They typically have 1 to 4 generations per year based on the weather. The first 3 to 5 hours of darkness in a day is when adult European corn borer moths are most active. It takes about 3 days after moths have emerged from their cocoons to start producing eggs. At this point, females will lay an average of 20 to 50 eggs per day for about 14 days straight. In a female moths lifetime they can lay from 280 to 700 eggs. In total, both male and female moths will live about 18 to 24 days. In areas with 1 to 2 generation annually, flight and reproduction happens between June-July and August-September. For 3 generation areas, flight and reproduction typically happens in May, late June, and August. Finally, in 4 generation locations adult moths are active from April, June, July, and August-September. The eggs that females deposited lay on the bottom part of leaves and in clusters of about 15 to 20 eggs. The eggs will develop when the temperature is around 15˚C, taking about 4 to 9 days to hatch. European corn borer larva that emerges from these eggs goes through about 6 instar/molting stages. The larva first eats within the whorls. When the tassels start to grow the larva will emerge into the stalk and ears of corn. They do have a high mortality rate in the first few days from emerging from the eggs. Once they are established within a plant their servile rate drastically improves. In the last instar larva stage, European corn borers overwinter in host plant stems and stalks. Pupation of these insects typically happens in April or May and later in the year for areas where only one generation of European corn borers occur. To get through this stage of life, it takes 12 days when the temperature is about 13˚C.

European Corn Borers Identification and Habitat

Identification

The eggs of the European corn borers are creamy white in colour, oval, flattened and typically have a shimmering appearance. As the eggs begin to age they darken to beige or orangeish colour, measuring about 1mm long and .75mm in width. The larva that hatches from these eggs are normally pinkish gray or brown in colour, with a black to brown head, a brownish yellow thoracic plate and their bodies are covered with round dark spots. When European corn borers pupate, they are typically brownish yellow in colour. Male European corn borers pupas are about 2 to 2.5mm wide and 13 to 14mm long, whereas females are 3.5 to 4mm wide and 16 to 17mm long. The tips of these pupas abdomen have 5 to 8 recurved spines, helping them anchor to their cocoon. Adult male European corn borers are moths with a wingspan of 20 to 26mm wide, are darker in colour, typically brownish gray or pale brown with yellowish patches and dark zigzags on their bodies. For female European corn borer moths, they are light brown to yellow in colour with a wingspan that ranges between 25 to 34mm wide. Their wings are covered with dark zigzags as well as pale yellowish patches on them.

Habitat

There is a variety of host plants that European corn borers live and feed on. They will attack the healthy herbaceous plants that have stems big enough for the larvae to fit into. Their primary location of infestation is in corn. The only time other vegetables are infested is when there is a large infestation before corn is available, or later in the planting season when corn has become unattractive to the European corn borers. Some other host plants that can be damaged by European corn borers are lima and snap beans, aster, buckwheat, cosmos, dahlia, gladiolus, hollyhock, hop, millet, oat, peppers, potatoes, soybeans, and zinnias. There are also some weeds that have been known to host these insects such as barnyard grass, beggarticks, cocklebur, dock, jimsonweed, panic grass, pigweed and smartweed. If European corn borers are not managed, they can cause economic loss.

European Corn Borers Control Methods

Cultural Control

If you are looking to control European corn borers using cultural methods, it is best done by destroying their overwintering homes. This can be done by plowing at 20cm deep into the soil. Mowing infested areas close to the soil surface has been shown to reduce the infestation of larvae by 75%, and when combined with plowing can be extremely beneficial. It is important to understand that if minimal tillage is done, it will leave crop residue on the ground and will provide European corn borers with a suitable environment to live in and increase their rate of survival. Due to the fact that there are a lot of common weeds that European corn borers can live in, it is important that you manage the weeds that are in and around fields with potential host plants.

Chemical Control

Insecticides that are in liquid formulation are most commonly used to protect corn against European corn borers. It is recommended to apply liquid insecticides when eggs are hatching to have optimal control to prevent an infestation. If looking for control in a corn field, chemical application is best done when tassels are emerging. During this time of plant growth larva is actively feeding and will provide more control. An alternative insecticide to liquid chemicals is granular formulation which is more persistent; this can be put into the whorls for control of first generation European corn borer larvae.

Latin / Alternative European Corn Borers Names

  • - Ostrinia nubilalis

Sources

http://www.ent.iastate.edu/pest/cornborer/

http://entnemdept.ufl.edu/creatures/field/e_corn_borer.htm