Cherry Bark Tortrix

Cherry Bark Tortrix,(Enarmonia formosana) is a pest of practically all rosaceous trees including apples, cherries, plum and crabapple. Larvae feed under the bark causing the bark to loosen and crack. Surveys are conducted because of the presence of potential host material in Wyoming and potential introduction pathways from surrounding states. It has been found in Washington and Oregon. To date, it has not been found in Wyoming. Ninety-one total traps have been placed throughout twenty-three counties in Wyoming.

The forewings are mottled with dark and light browns. Along the front of the wing, there are strips of orange, dark purple, and silver. The larvae are typical caterpillar-shaped and are usually transparent, with a pinkish lining in the gut. Mature larvae reach the lengths of one to 1 ½ inches. The eggs are very small, oval and salmon pink.

Hosts : The common name is somewhat misleading as this insect attacks most tree fruits, not just cherry. Its hosts also include plum, peach, nectarine, apricot, almond, apple, crab apple, pear and ornamental cherry. In England, it is primarily a pest of older trees that are more likely to have winter injury or wounds. Stone fruit trees, which tend to have more bark injury, may be more vulnerable than other fruit trees.

Life Cycle: The adult moth is active from April to September and has one generation a year. It flies mainly in the early morning but also during the day. Mated females lay eggs on the bark of the tree, often near wounded or previously infested areas. Pruning scars and winter damaged areas are likely targets. Each female lays about 90 eggs, which hatch within 2 to 3 weeks. The larvae, which pass through five instars, feed beneath the bark, making irregular tunnels. Cherry bark tortrix overwinters as a larva, which pupates the following spring. After the adult has emerged, the cast pupal skin protrudes from the tunnels in the bark.

If you are so lucky to run across the inch-long adult moths, they are rather beautiful. The forewings are mottled with dark and light browns. Along the front of the wing, there are strips of orange, dark purple, and silver. The larvae are typical caterpillar-shaped and are usually transparent, with a pinkish lining in the gut. Mature larvae reach the lengths of one to 1 ½ inches. The eggs are very small, oval and salmon pink.

There is one generation of CBT per year in the Northwest. Adults fly and lay eggs from April to September. Females deposit eggs in cracks, crevices, wounds, crotches and lenticels small natural opening of the bark of trees. Eggs hatch after a couple of weeks and the first caterpillar stage forages for entrance into the tree bark. Once the larva gains entrance through an opening in the bark, the caterpillar will burrow deeper into the living tissue of the bark down to the cambium. Here the larvae feed though out the season until next spring. The caterpillars mine out winding tunnels in the bark. During mining, the larvae are constantly constructing a frass tube. The tube is built on the entrance to the tunnel and consists of frass digested food and silk. The frass tube is a unique adaptation that offers: protection from predators gaining access to the tunnel, protects the caterpillars from the outside environment and a safe site to pupate.

Damage: First instar larvae feed on the bark and outer sapwood while the 2nd through 5th instars make tunnels between the bark and cambium, but do not penetrate the hard wood. Infestations usually occur upward from the base of the tree. Infestations are easily recognized by reddish-orange colored frass accumulations or frass tubes near gallery entrances.

Larvae damage trees by direct feeding which reduces or excludes transportation of nutrients to the roots. The feeding causes exudation of gum and deformation of bark growth on the main branches and trunk. Along infested sides of the tree, dieback of new and old growth can occur from the portion girdles. Indirect damage occurs through the formation of habitats for secondary pests such as bark beetles, fungi, and increasing susceptibility of infested trees to successive years of freezing damage, which can result in the death of the tree.

Monitoring : A simple, but time consuming method of monitoring is to examine injured bark for signs of gummosis and frass. Frass can easily be seen at tunnel openings in late winter and early spring. However, several native clear-wing moths in the Sesiidae family cause similar damage to the trunk and scaffold limbs. To identify the pest, the larvae must be collected and examined.

Cherry bark tortrix is attracted to a blend of tortricid pheromone components. Use of pheromones can simplify monitoring in regions not know to be infested, but they are not useful in managing established infestations due to the long flight period of adults.

Controls: Control aimed at adults is not practical because of the prolonged flight period. Most of the available information on control of the pest is outdated. In England, spring treatments aimed at killing larvae as they came to the surface of the bark to pupate were not successful. Another approach in England in the 1960s was a dormant season treatment aimed at the overwintering larvae using materials such as tar oil, creosote or insecticides. However, the treatments were extremely labor intensive, as the materials were brushed onto the tree after the bark had been scraped, and the insecticides used are no longer available. Materials currently used for sesiid borers, such as the peachtree borer, may be effective.

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