Wednesday, June 6, 2012

Keith Mickler: Slamming the door on corn earworms

By Keith Mickler
County Coordinator

The corn earworm is the most vicious and widespread pest of corn. The same little critter is also known as the tomato fruit worm when on tomato, and cotton bollworm when visiting cotton.
DescriptionAdults are light tan moths with 1-1/2 to 2 inch wingspans while the larvae are light yellow, green, pink, or brown, and 1 to 2 inches long, with white and dark stripes on the sides, yellow heads, and black legs. Eggs are yellow or white, round, and ribbed.
LifecycleThe Pupae overwinter in the soil. Adults will emerge in early spring and can migrate long distances. Females lay eggs on undersides of leaves or tips of corn ears. Eggs will hatch in 2-10 days with larvae feeding for 2-4 weeks, and then pupate in the soil. Adults will emerge again in 10-25 days. There can be 1 to 4 generations per year.
The larvae feed on fresh silks, and then move down the ears eating kernels and leaving trails of well you know, stinky. On tomatoes, larvae eat buds, chew large holes in leaves, and burrow into the ripe fruit.
Cultural and/or chemical methods are available to combat these dreaded corn earworms.

Cultural Control: Plant corn which is resistant to earworm. Corn varieties with long, tight husk are physically safer from earworms. Check with your local garden center for resistant varieties; a few varieties are: Country Gentlemen, Staygold, Golden Security, and Silvergent.

Place a clothes pin at the point where the silks enter the ear to help keep worms out. This also should be done soon after the first silks emerge.

Early season plantings are damaged less because the corn matures before earworm populations explode.

In the fall, till the soil where your corn was growing, this will help expose the pupae to winter temperatures and destroys their exit tunnels in the soil which larvae built. Now they are trapped under the soil. Poor little helpless earworm, bless its little heart!!!
Chemical: Use insecticides containing bifenthrin, carbaryl or spinosad. Mix the insecticide in a sprayer with water (according to the insecticide label) and apply the spray at the center third of the plant which is area that needs to be protected. This preventive program against corn earworms should begin when 10% of the ears are silked. Repeated sprays at three to five day until 90% of the silks have turned brown, this should give great control. One gallon of spray should treat 150 to 200 feet of sweet corn. It is critical to protect the ears of corn from early-silking until the silks turn brown.

Organic: Apply 5 drops of mineral oil, corn or soybean oil (apply only once) to corn ear tips when the silks begin to turn brown not before because the oil will interfere with pollination. If the eggs and larvae survive the oil barrier use a knife to cut off the ugly worm eaten parts of the corn before cooking, or not. Corn earworms can add some protein to your corn, if you're into eating worms.

Keith Mickler is the County Coordinator and agriculture agent for The University of Georgia/Floyd County Cooperative Extension. Located at 12 East 4th Ave, Rome, GA 30161 (706) 295-6210. Office hours are Monday-Friday 8:00 a.m. - 5:00 p.m. The University of Georgia Cooperative Extension - Learning for Life. Agriculture and Natural Resources, Family and Consumer Sciences, 4-H Youth.  An Equal Opportunity/Affirmative Action Institution. To obtain extension publications please visit our web site or contact your county Cooperative Extension office.

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