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  Lawns > Fescue > Orange-striped Oak Worm

Fescue

Orange-striped Oak Worm

"Here today - gone tomorrow" is an apt description of oak tree branches having a population of orange striped oak worms. These caterpillars are basically a "stomach with legs", so leaves disappear rapidly during the weeks they feed. The caterpillars are two to three inches long, with yellow-orange stripes running the length of their body. White bristles emerge along the body, above the legs.

The orange striped oak worm is sometimes confused with the yellow necked caterpillar. The coloration may be similar, but the yellow necked caterpillar responds to stress differently. When the branch they are feeding on is tapped, the yellow necked caterpillar will quickly raise its neck and head - as if to look around to locate the intruder. The orange striped oak worm keeps its head down, munching lunch!

Because the oak worm ingests such tremendous amounts of food, one of the ways it is discovered is the thickly scattered waste pellets that fall from tree foliage. On a quiet day, the pellets can be heard clattering down through the leaves and hitting the ground below.

Fortunately, poisons are rarely needed. Mother Nature provides a lifespan of only a few weeks before the caterpillar drops to the ground and pupates. If the fecal pellets are objectionable, an organic control works well. Bacillus thuringiensis (B.t.) is a disease spore sold as Dipel, Thuricide, Caterpillar Attack, etc. This spore is harmless to mammals and birds but it causes caterpillars to stop feeding as soon as they ingest it. After a few days, dead caterpillars will hang limply from the formerly disappearing leaves.

ORANGE-STRIPED OAK WORM


Henning von Schmeling, naturalist at the Chattahoochee Nature Center, pointed up into a small tree. “My oak tree is disappearing!” he exclaimed. “And here are the sorry culprits!”

Looking upwards, I could see the source of his displeasure. The leaves of his fifteen-foot tall red oak were in tatters. Crawling on almost every leaf were two-inch long, olive-colored caterpillars having two yellow-orange stripes along their backs. Henning and I both realized that Orange-Striped Oak Worms were making a meal of his Nature Center trees.

OAK WORMS These fall caterpillars are the offspring of a moth who laid her eggs on the tree several weeks ago. At first, the damage from the tiny worms was undetectable. As they grow larger, it is easy to see where they dine. Since it was a small tree and the Chattahoochee Nature Center believes in using organic alternatives, I advised Henning to use a product containing (BI)Bacillus thuringiensis (EI). This caterpillar disease spore is easy to find at garden centers and is harmless to birds and mammals. If the infestation had been on a larger tree, which would soon lose its leaves anyway, I might have advised leaving the caterpillars alone.

ORANGE STRIPED OAK WORM

This insect is most recognized in the caterpillar stage because of its defoliation of oak trees. The full grown caterpillars are 1 1/2 to 2 inches long, black in color with several narrow, yellow or orange stripes down the length of their body.

The orange-striped oak worm caterpillar generally appears in Georgia in August and September. They sometimes completely defoliate smaller oak trees. This insect is extremely troublesome when present in oaks over patios, driveways, etc., because of the large amount of excrement from the insect's body.

The winter is passed in the pupa stage in the ground. The moths emerge from June-August and mate. The females deposit their eggs then on the underside of oak leaves.


CONTROLS

Non-chemical control

Usually there is only one generation per year and control measures are not necessary. Since oak trees lose their leaves naturally in the fall, even complete defoliation does little harm.

Chemical control

If control measures are necessary, Sevin will give adequate control. Organic caterpillar poisons such as Dipel or Thuricide work well. As with all pesticides, follow directions and precautions listed on the label.






 



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