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Oak Leafroller



Species: Archips semiferana (Walker) [Lepidopters: Tortricidae]

Distribution:

This native insect periodically builds up large populations that may defoliate vast acres of oaks from New York to Michigan and south to the Carolinas.

Hosts:

This leafroller prefers red and pin oaks.

Damage:

Forest outbreaks usually last a few years and landscapes nearby may also be affected. They characteristically roll up the leaf margin until the tip half of an affected leaf is rolled up. The larvae skeletonize the leaf within the protection of the rolled up section. However, when severe outbreaks occur, entire leaves and leaf buds may be eaten. This can result in dieback of oak branches and stressed trees are often susceptible to attack by the twolined chestnut borer.

Description and Life Cycle:

Oak leafrollers spend the winter in the egg stage. The eggs are laid in masses of 40 to 60. They are attached to the bark, usually to the side or just below a twig crotch. The flattened eggs are covered with tan scales applied by the female moth. The masses are about 1/4-inch in diameter. The eggs hatch in late April to mid-May and the greenish-yellow larvae with black head capsules crawl to the expanding leaf buds. The young larvae spin some loose webbing round the expanding leaves and they feed by skeletonizing or chewing the leaf margins. Several larvae may cluster within these loose webs. As the larvae mature, the are able to roll the leaves into cylinders kept together with silken threads. When disturbed, the larvae may rapidly wiggle out the other end of the rolled leaf and drop down on a strand of silk.

By mid- to late June, the larvae have reached 3/4 to one inch in length and are still yellow-green with black head capsules. The larvae pupate within the rolled leaf and the brown pupal case is firmly attached with silk. After 10 to 14 days, the adult moths emerge. Adults are about 3/8 to 1/2-inch long and are tan to yellowish in color. They usually hide on the undersides of leaves during the day but readily fly if the branch is disturbed. They are strongly attracted to lights at night. After mating, the females lay their egg mass within a couple of days of emergence. The rest of the year is spent in the egg stage since only one generation per year occurs.

Control Hints:

This pest rarely damages landscape oaks sufficiently to warrant controls but solid stands of red and pin oaks in parks, roadside areas and forests may need protection. In larger acreage, aerial spraying is necessary to achieve satisfactory control.

Strategy 1: Biological Control - Spray with Bacillus thuringiensis (Bt) - This bacterium is marketed as Dipel, Thuricide and similar products. The bacterium is quite effective if sprayed while the caterpillars are young and forming their first webs within the opening oak leaf clusters. Larger larvae within the protection of their rolled leaves are often resistant to the bacteria's toxin.

Strategy 2: Chemical Control - Spray Standard Insecticides - Numerous insecticides are effective for control of this pest, but applications have to be made before the larvae completely roll up the leaves.