Fruittree Leafroller

The fruittree leafroller is most often a problem on apples, but also attacks apricot, cherry, pear, plum, prune, quince, raspberry, currant, loganberry, blackberry, gooseberry, English walnut, ash, box elder, elm, locust, oak, poplar, willow and rose.

Adult fruittree leafroller moths are about 0.5 inch long, with rusty brown wings marked with areas of white and gold. When at rest the adults show the typical bell-shaped pattern common to the family Tortricidae. The eggs are laid in masses on limbs and twigs and are covered with a gray secretion that turns white upon aging. Larvae are green with a black head. The intensity of the green color varies from a light green in young larvae to a darker green as they mature. Fruittree leafroller larvae are difficult to distinguish from the more damaging obliquebanded leafroller larvae.

The fruittree leafroller overwinters in the egg stage. Eggs usually hatch in early spring. Larvae feed within opening buds. As they mature they tie leaves together and feed on leaves, blossoms, and small fruit. Adults emerge in May or June. These adults then lay egg masses that overwinter. There is one generation per year.

Life cycle:The fruittree leafroller spends the winter in the egg stage and has only one generation a year. Other leafrollers spend the winter as larva in protected places on the host and have two or more generations.The fruittree leafroller overwinters as eggs laid on branches or twigs. Eggs hatch into tiny larvae from March to as late as mid-May in cooler areas. Larvae feed on leaves for about 30 days then pupate in a loose cocoon, which they form in a rolled leaf or similar shelter. Eight to 11 days later the adult emerges from the pupa. The moths live only about a week, during which time they mate and lay eggs. They fly from May to June, depending on locality, and in any one area the flight usually lasts about three weeks. These moths lay eggs on twigs and branches, and the eggs will remain there until they hatch the next spring.

Omnivorous, obliquebanded, light brown apple moth, and most other problem leafrollers overwinter primarily as larvae in protected places in trees. For example, omnivorous leafroller often overwinters in or on old, unharvested fruit, whereas obliquebanded leafroller often is found as second- or third-stage larvae under bud scales. They pupate in spring, emerge as adults, and sometimes lay their first eggs on weeds. The second generation of these leafrollers, which occurs in June or July, is more likely to occur on trees, causing damage later in the season than the fruittree leafroller.

Damage:Leafroller larvae feed on tender, new leaves, giving them a ragged appearance; they also roll and tie leaves together with silken threads to form compact hiding places. Some years very large populations develop. In severe cases larvae can partially or completely defoliate trees, and their numerous silken threads can cover the entire tree and the ground below. Also, larvae frequently drop to the ground on their silken threads and can defoliate other plants beneath the trees. However, even completely defoliated trees can recover if they are otherwise healthy, with the exception of newly planted and first-leaf trees.Oaks in the Central Valley can be particularly hard hit by the fruittree leafroller. Some people mistake this leafroller for California oakworm because of its prevalence on oaks. However, oakworm is a more serious pest in coastal areas, while the fruittree leafroller does the bulk of its defoliation damage to oaks in the Central Valley. The larvae of all leafroller species also attack fruit on trees, and young fruit might fall because of deep feeding grooves larvae make just after the fruit has formed. Less severely damaged fruit remain on the tree and develop characteristically deep, bronze-colored scars with roughened, netlike surfaces that are mostly cosmetic, although the fruit can become deformed. They do not enter the fruit as do codling moth or Oriental fruit moth.

The larvae of all leafroller species also attack fruit on trees, and young fruit might fall because of deep feeding grooves larvae make just after the fruit has formed. Less severely damaged fruit remain on the tree and develop characteristically deep, bronze-colored scars with roughened, netlike surfaces that are mostly cosmetic, although the fruit can become deformed. They do not enter the fruit as do codling moth or Oriental fruit moth.The larvae of all leafroller species also attack fruit on trees, and young fruit might fall because of deep feeding grooves larvae make just after the fruit has formed. Less severely damaged fruit remain on the tree and develop characteristically deep, bronze-colored scars with roughened, netlike surfaces that are mostly cosmetic, although the fruit can become deformed. They do not enter the fruit as do codling moth or Oriental fruit moth.

Control:A number of insects eat leafrollers including certain tachinid flies and ichneumonid wasps, which parasitize the larvae. After consuming the leafroller larvae, the braconid wasp forms a white cocoon next to the shriveled up worm inside its nest. A white cocoon is an indication that the parasite is present and might provide control. Lacewing larvae, assassin bugs, and certain beetles also are common predators. Birds sometimes feed on the larvae and pupae, although they usually prefer other insects. These natural enemies often help to keep leafrollers at low, nondamaging levels, but even if natural enemies are present, large outbreaks of leafrollers occasionally occur.

The best strategy to manage leafrollers is to control larvae of the overwintering generation in spring. Conventional insecticide applications in the delayed-dormant period (at half-inch green tip stage of apple flower bud development) have given the best control of pandemis leafroller. Bacterial insecticides-strains of Bacillus thuringiensis (Bt)-have given good control of leafroller larvae when 2 or 3 applications have been made in the period from tight cluster through petal fall. In summer, insecticides can be used to control either adults or larvae. Sprays targeting adults should be timed at peak moth flight. In most years, the second cover spray directed at codling moth coincides fairly well with the peak flight of pandemis leafroller adults and is a reasonably good timing for adult control. Peak pandemis moth flight can be predicted using degree-days. The first moths emerge about 950 degree-days after January 1. First moth capture in pheromone traps is used as a biofix, similar to the codling moth model, to predict future events in the life history of pandemis leafroller. At biofix, the degree-day value is set at zero. Moth flight peaks between 200 and 220 degree-days after first catch.

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