Apple Clearwing Moth
(Synanthedon myopaeformis)

Growers in the Similkameen and Okanagan valleys should be on the look out for a new pest of fruit trees - the apple clearwing moth. The presence of this European pest was confirmed in the Similkameen Valley in 2005 on apple as the first record in North America. Growers should report any suspicious damage to Hugh Philip (250 861-7230) or their field service/crop advisor to confirm if this pest is present in their orchard.

Hosts

European hosts include apple, pear, crabapple, quince, plums, apricots, cherries, hawthorn, and mountain ash.  This pest is also known as the small red-belted clearwing moth in Europe.

Damage

Larvae tunnel under the bark anywhere from below the crown area up to branches. Infested rootstocks appear swollen. To date infestations have been found in M9 and Ottawa 3 rootstocks below the graft union and under burls or around cankers above the graft union. In Europe infestations are often associated with European canker caused by Nectria galligena, and with M9 rootstock. There is no information on the effect its feeding has on tree development and fruit production in BC. In Europe it can shorten the life of trees and could make the trees susceptible to attack by other insects (such as shothole borer).

Larval damage to crown area of young apple tree.

Identification

Larva - about 15 - 20 mm long, dirty white with reddish-brown head and thoracic shield behind head.

Pupa - 15 mm long, pale yellowish-brown.

Adult - 20-25 mm wing-span, slender dark blue-black body with bright red band across the first abdominal segment (behind base of wings). Wings are transparent (lack scales), the front pair narrow, shiny and slightly dark; hind wings are much shorter, triangular with definite markings.

 

Apple clearwing moth adult.  Photo courtesy Christina Machial	Apple clearwing moth larvae

Life History

There is no information on the life history of this insect in BC. In Europe there are one or two generations per year depending on conditions. Adults are active from May to September depending on country (from Scandinavia south to northern Africa). In 2005 in the Similkameen Valley, adults were first noticed in mid June. Eggs are laid singly in burr knots, pruning cuts and wounded bark on branches and trunks, and likely any other site that allows larvae to get under the bark. Older references report apple clearwing infestations associated with wounds caused by woolly apple aphid. The tunnels are shallow, irregular winding galleries just cutting into the wood, and about 20 – 25 mm long. Frass collects in the tunnels and is rarely expelled by larvae. The larvae overwinter in the tunnels and pupate the following spring at the entrance of the tunnels. When the moths are ready to emerge (mostly in the morning), the pupae wriggle to the tunnel exit hole and extend out to allow the adults to emerge. The appearance of empty pupal cases sticking out of the bark is a useful indication of its possible presence.

Monitoring:

The moths can be observed resting during sunny days on leaves. To check for larval infestations, examine the bases of trees for 2 to 3 mm-wide holes and tunnels under the bark, especially rootstocks that appear abnormally swollen.

Peach tree borer pheromone traps will attract apple clearwing male moths. Research is underway to identify the pheromone blend of apple clearwing moths from the Similkameen Valley. There are North American sources of pheromone lures marketed for apple clearwing pheromone traps.

The Canadian Food Inspection Agency will be conducting a survey in all apple-growing regions of Canada in 2006 for the presence of the moth using pheromone baited traps.

Control:

Cultural - According to European sources, reduce the risk of infestations by minimizing wounds to trees, removing young trees with cankers, and sealing wounds with wound-protecting products. Wrapping the base of trees with polyester batting (a pillow stuffing product) will discourage egg-laying and prevent escape of emerging adults.

Chemical – At present there are no products registered for control of apple clearwing in North America. It is expected that the Isomate-P mating disruption product may provide protection if applied before the first appearance of adults.

March 2006