Oak Leaf Roller and Springtime Defoliation of Live Oak Trees

More importantly, these stressed trees aremore susceptible to attack by various diseases andinsects. Weakened trees are extremely susceptibleto wood-boring insects such as longhorn beetles,flat-headed tree borers, shot-hole borers and manyclear-winged tree borers. (For more informationon these insects, see the Texas CooperativeExtension publication B-5086, Wood-Boring Insectsof Trees and Shrubs.)If the trees are completely defoliated yearafter year, especially under the drought conditionsthat are common across Texas, they will die.Life cycleThe adult mothof the oak leafroller, Archips semiferana,is about 1/2inch long. Its wingsare mottled brownwith dark brownmarkings. Sparganothispettitana (nocommon name) haslemon yellow wingsand ranges from 1/2to 3/4 inch long.Both species undergo one generation eachFig. 3. Oak leafroller moth (left) andpupal skin (right).year. In May, moths of both species lay their eggson the twig tips and leaf buds of several differenttree species. The eggs remain on the buds or twigsfor about 10 months and begin to hatch in mid-March.Once they hatch,the caterpillars, or larvae,feed on the tendernew spring growth ofthe trees from mid-March until late April.The larvae are creamywhite to greenish andhave dark black orbrown head capsules.They develop throughseveral stages, orinstars, as they matureto about 3/4 inch long.Fig. 4. Oak leaf roller mothlarva (above) and adult (below.)Trees that are heavily infested will usually bedefoliated by mid- to late April, when the fullygrown caterpillars form the pupa stage on the tipsof twigs, in bark crevices or on weeds and otherplants growing near the infested trees.Fig. 5. Oak leaf roller, Archips semiferana (Walker) (Lepidoptera:Tortricidae) adult (left), pupal skin (center) and caterpillar(right), collected from oak trees, March 2002.At about the first of May, moths begin toemerge from the pupal stage (cocoon) and beginlaying eggs on the twigs of oak, hackberry, pecanand walnut trees. These eggs will again remaindormant until the following March, thus completingthe 1-year life cycle.ManagementFor most oak trees throughout the HillCountry, it is not feasible to use insecticides tocontrol the oak leaf roller and its related species.Often the best course of action is to simply donothing. Post oak trees have survived in South andCentral Texas without human interventionthrough time, despite periodic pest outbreaks andresulting defoliation. Caterpillar pest populationsare generally cyclic, and they rarely occur yearafter year.The oak leaf roller doeshave a few natural enemies.The best natural controlappears to be provided byseveral types of parasiticwasps that attack and kill theoak leaf rollers. However,there are seldom enough ofthese wasps to curtail an outbreak.Certain birds, includingmockingbirds, have alsobeen observed feeding on thedangling caterpillars.Fig. 6. Close-up of oakweb worm caterpillar.2