Forest Preserve District of Cook County, Illinois
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The Codling Moth or Apple Worm
Nature Bulletin No. 397-A   November 28, 1970
Forest Preserve District of Cook CountyGeorge W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation

The sight of an orchard bending heavy with apples ready to be picked, and then of the boxes, baskets and heaps of perfect spicy-smelling fruit in stores and roadside stands, gives most people the idea that apple farming must be an easy life. Nothing could be farther from the truth. The puts in years of year-round labor, care, worry and expense before he harvests the first apple. Ever after his trees are grown and a crop can be expected, bad weather, diseases and pests, or marketing troubles, often throw him for a loss. Commercial apple growing is so complicated that orchardists and apple specialists seem to speak a language of their own.

Apples can be attacked by dozens and dozens of diseases and pests requiring many kinds of special treatment and precautions. A few of the damaging diseases of Illinois orchards are apple scab, apple blotch, cedar rust, quince rust, fire blight and bitter rot. Trees may be killed or injured by mice and rabbits nibbling the bark, and the European red mite causes the leaves to turn sickly and drop off. Insect pests, too numerous to mention, include grasshoppers that chew fruit and foliage, the 17-year cicada that kills the twigs, borers that destroy the trunk, leaf rollers, leaf hoppers, aphids, scale insects and a snout beetle that makes apples knotty and undersized. But the most serious of all is the Codling Moth which if uncontrolled can destroy over 90 percent of the crop.

The codling moth or Apple Worm is a pinkish-white caterpillar or larva that causes those worm holes in the sides or blossom ends of apples that lead into the core. When a half-inch long or more, it leaves the apple and crawls under a bit of loose bark or other cover and spins a tough silky whitish cocoon where, if late in the season, it remains until spring. Then it changes into a yellow-brown pupa which, after a month, emerges as an adult moth with a wingspread of about three-fourths of an inch. The forewings have alternate wavy brown-and-bluish gray lines that give the appearance of watered silk. The hind wings are coppery. During the next ten days the female, after mating, lays 50 or more little flat eggs about the size of pin heads on young apple leaves. In a week or so these hatch into tiny larvae that crawl onto young apples and gnaw their way inside where they eat and grow for another month. In the orchards of Illinois there are two and sometimes three generations a year.

The codling moth is a native of Europe and was brought to the eastern United States along with apples before 1750. It spread westward, reaching Iowa by 1860, Utah by 1870 and California in 1874. Besides apples, the codling moth damages pears, quinces, red haws and even English walnuts.

Lead arsenate has been the standard insecticide since the early 1900's. But, as the apple worms developed an immunity, they became more and more abundant and harder to control. Unfortunately, this makes it necessary for apple growers to carefully wash and treat the fruit because both lead and arsenic can be dangerous to health. Even then, losses to American orchardists due to apple worms amounted to 25 million dollars, and the cost of their control to another 25 million. In recent years the use of DDT has reduced these losses greatly but it, also is poisonous to man and must be used with caution.

But, what is worse than finding a worm in a nice red apple you just bit a chunk out of ? Only half a worm.

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