Corn Borers
Facts about European Corn Borers
Going back almost 100 years marks the first known recognition of European corn borers in the United States, although it is thought they had already been here some time without notice. Since that time, the pest has become only too well known, as its population has spread to include territory to the Rocky Mountains.
Depending on the location, the adult moth can have up to four generations. On the east coast of Maine, one with a possible second generation is normal, while in the grain belt of Nebraska up to four generations are common. The life cycle of the European corn borers remain the same regardless of their location. An egg mass is deposited on the underside of a leaf from a corn plant; yellowish white in color in an overlapping pattern. The colored eggs become more and more translucent as the larvae within develop; over time, the black head of the caterpillar becomes evident, giving a clue that the hatching is about to occur. Chewing their way out from their egg, the larvae immediately traverse to the developing leaves where they commence feeding voraciously. As larvae, the European corn borers will endure five instar stages; growing larger and shedding old skin as the new, roomier skin takes over.
Around the third instar stage, the European corn borers dismiss the leaves as a food source and proceed to the stalk, ear shank or ear to begin feeding there. The larvae reaching this stage may either delay further development as winter approaches in the eastern states, or may undergo the 4th instar before pupating into a 5th instar stage in Midwestern states. The pupae stage generally takes place within the plant stem, but occasionally will occur on a corn leaf as well.
The adult moth will emerge from the pupa stage and generally congregate in nearby fields where low growth is detected. They may mate within the corn field itself as well. The females give off a pheromone which is designed to attract the male moth. The moths are approximately one inch long, with one inch wing lengths, with the female being slightly larger than the male. Coloration is also different between the sexes; yellowish brown for the females and darker brown for male moths. Egg laying occurs about one month after leaving pupae in eastern states, with females depositing eggs in groups of 20 or so until as many as 500 eggs have been laid. The next generation of European corn borers will now be well on their way to ruining another crop of corn.
Attacks by European corn borers can not only result in crop yields, but entire harvests as well. Continuous inspections of corn crops are conducted regionally to identify stages of the destructive pests to minimize its damage.