Baldcypress leafroller adultWhitney Cranshaw, Colorado State University, Bugwood.org
Leafrollers, which can feed on leaves and flower buds, are generally minor pests in ornamental nursery crops but can be a serious defoliating pest when populations are high. In spring, small larvae spin webs and feed on new foliage. They can attack a wide variety of trees including deciduous and live oaks, ash, birch, California buckeye, box elder, elm, locust, maple, poplar, and willow. Roses can also be targets.
They get their name from how the caterpillar-form larvae roll a leaf and web it together to form a protective shelter.
Source: University of California Agriculture and Natural Resources, IPM
Fruittree leafroller adultBugwood.org; Gerald J. Lenhard, Louisiana State University, Bugwood.org
facts about leafrollers Identification: At maturity the larvae are 0.75 to 1 inch long. When disturbed, they wiggle backwards and drop to the ground on a silken thread. The pupa is just under 0.5 inch long, light to dark brown, and is usually formed within the rolled leaf. The adult moth has a wingspan of less than one inch. Like other leafrollers, its wings have a bell-shaped outline when viewed from above. The forewings are mottled shades of brown and tan with gold-colored flecks, while the hind wings are whitish to gray.
Life cycle: Fruittree leafrollers have one generation per year. Overwintering eggs hatch in spring, and larvae can be found feeding on leaves until about June. The larvae are dark green caterpillars with black heads. Adult moths appear in June or July and lay the overwintering eggs.
Biological Control: A number of general predators, such as lacewing larvae, assassin bugs, tachinid flies, and wasp parasites attack leafroller larvae or eggs. These natural enemies help keep leafroller populations at low, nondamaging levels, but occasional outbreaks occur. Preservation of natural enemy populations is an important part of keeping leafroller numbers low. Use selective materials that are least disruptive of biological control when treating these and other pests.
Baldcypress leafroller larvae Chemical control: If damaging populations are observed, several environmentally-friendly chemicals are effective in controlling this pest, including Bacillus thuringiensis (Bt) and Spinosad. Bt is only effective on fruittree leafroller larvae when they are small (less than 0.5 inch long) and usually requires more than one application. Caterpillars must ingest the pesticide to be killed. Spinosad is a material that is effective on young larvae and is often preferred over Bt because it has a longer residual and slightly more efficacious against older larvae. Optimum control and a minimum amount of damage by leafrollers occur when a spray is applied at the time of larval hatching or shortly afterwards. To determine this time, inspect twigs showing flushes of new foliage and look for feeding injury and the small caterpillars. If egg masses are found, check them regularly for signs of larval exit holes. High-pressure spray is needed to force the material into the leaf rolls and other protected areas where larvae are found.
