Ministry of Agriculture
Apple Clearwing Moth
The apple clearwing moth (known as small red-belted clearwing moth in Europe) is a new pest in the Similkameen and Okanagan valleys of British Columbia. The presence of this European pest was confirmed in an organic orchard in Cawston in 2005 on apple as the first record in North America. It has since been recorded in Keremeos, Oliver, North Osoyoos, Kelowna and Coastal B.C. Growers should report any suspicious damage to their field service/crop advisor to confirm if this pest is present in their orchard. To help stop the spread of this new pest, do not move fruit trees and rootstocks from infested areas.
European hosts include apple, pear, crabapple, quince, plums, apricots, cherries, hawthorn, and mountain ash.
Larvae tunnel under the bark anywhere from below the crown area up to branches. Infested rootstocks appear swollen (see figure 1). Infestations have been found mainly in M9 and Ottawa 3 rootstocks below the graft union and under burls or around cankers above the graft union, but all apple rootstocks and varieties are attacked. Top-grafted Ambrosia trees are more susceptible to attack and feeding by larvae can kill young trees. In the drier desert climate of the Southern Interior, infested trees are prone to drought stress which can contribute to death of trees. In highly infested orchards, damage can spread to tree canopies. 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 B.C. In Europe it can shorten the life of trees and could make the trees susceptible to attack by other insects (such as shothole borer and ambrosia beetle).
|Fig. 1. Larval damage to crown area of young apple tree.|
Larva - about 15 - 20 mm long, dirty white with reddish-brown head and thoracic shield behind head (see figure 3).
Pupa - 15 mm long, pale yellowish-brown.
Adult - 20-25 mm wing-span, slender dark blue-black body with orange-red band across the abdomen. Wings are transparent (lack scales), the front pair narrow, shiny and slightly dark; hind wings are much shorter (see figure 2).
|Fig. 2. Apple clearwing moth adult. Photo courtesy Christina Machial||Fig. 3. Apple clearwing moth larvae|
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 the Similkameen Valley, apple clearwing moth has a 2-year life cycle. Adult flight begins in early June, peaks by mid July and flight ends in late August. Females feed on nectar for a few days before laying eggs. 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. Larvae feed on the cambium layer of trees for almost two years before pupation. Larval feeding leads to the creation of 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 (see figure 4). Counts of pupal cases can be used to estimate population density.
|Fig. 4. Apple clearwing moth pupal case. Photo courtesy of Okanagan Tree Fruit Company||Fig. 5. Apple clearwing moth cocoon (left) and pupa (right). Photo courtesy of Hugh Philip|
The moths can be observed resting on leaves during sunny days. 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. Delta or wing traps baited with peach tree borer pheromone will attract apple clearwing male moths. Research is underway to identify the pheromone blend of apple clearwing moths from the Similkameen Valley (Gary Judd, AAFC).
|Fig. 6. Apple clearwing moth trap. Photo courtesy of Okanagan Tree Fruit Company||Fig. 7. Fruit juice bait trap, Courtesy Gary Judd, AAFC Summerland|
Cultural - 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.
Mass trapping - Two litre plastic bottle traps (figures 6, 7) baited with grape juice have been shown to be highly attractive to both male and female clearwing moths (Gary Judd, AAFC). The trap has been painted yellow to increase its attractiveness to moths. Moths should be cleared out regularly.
Mating disruption - Isomate-P for mating disruption is not effective for reducing established populations. New dispensers developed by Pacific Biocontrol are being tested at the Pacific Agri-Food Research Centre, Summerland.
Biological control - Braconid parasitoids have been collected from larvae, but are not yet identified. The Pacific Agri-Food Research Centre, Summerland is evaluating nematodes for efficacy against the larvae.
Chemical control - There are no pesticides currently registered specifically for management of apple clearwing moth.
An emergency registration has been granted for trunk applications of Entrust (spinosad) in both organic and conventional orchards for the 2009 season (May 15, 2009 to Aug. 31, 2009). Results from trials conducted in the Similkameen indicate that Entrust provides good control of apple clearwing moth and it is expected that a Minor Use registration will be approved in 2010.
Screening trials for other products are being conducted by AAFC-Summerland.
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