Farmer's Guide: European Corn Borers

Corn leaves riddles with shot gun blast type holes? Sawdust like material in holes in the corn stalk? Could be european corn stalk borers. Learn more.

What is it?

The european corn stalk borer is known as ostrinia nubilalis. Typically these pests are prefer cold, rainy weather and they also feed on potato, tomato and pepper plants in addition to corn plants.

What does it look like?

European corn stalk borers are usually a pinkish colour but some can appear to be more burgundy and or a paler pink in color. Typically european stalk borers grow to the length of one inch and some european stalk borers also have pinkish or reddish stripes along the length of their backs. However, all european stalk borers have dots down the length of their backs and they have dark brown heads. The stripes or bands are rarely white and the contrast of these stripes may be your only indication that the worms are present, aside from plant damage or if you see the characteristic brown head poking from within a hole. Corn plant damage from european stalk borers will appear as chewed or ragged leaves and the stalks may not produce ears of corn. Those corn stalks which are infested and do produce ears of corn will produce them either distorted or the ears will be curled and bent in shape. The stalks of corn plants infested with european corn borers may also have holes which are filled with a sawdust like material.

How does it manifest?

European stalk borers can spend the winter as eggs on grasses and weeds such as ragweed. After over wintering they hatch when conditions become warmer in the spring. At this point the worms feed on the leaves and bore into the bases and sides of the corn stalks. A cross section of an infested plant would reveal a bored tunnel that goes upward from the original entrypoint and often contains swadust like material the european corn stalk borers have left behind while feeding. Once they have fed for several weeks, the worms then pupate in the soil and emerge as adult moths. Fortunately, european stalk borers typically only produce one generation per growing season and as they prefer cold, rainy weather there larvae as often washed away from corn plants at the point of hatching which reduces the eropean corn borer population in your garden.

What can you do about it?

European corn stalk borers usually cause damage before you notice their presence. Your best bet is to wait until the ears are at about 10% silk and make sure that you clear all debris and nearby weeds and plants from the garden. At 10% silk you can apply an insecticide in dust or spray formulation which contains either rotenone or carbaryl. You can safely repeat applications at 7 day intervals until no further damage is noted and no european corn stalk borers are seen.

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