Cherry Bark Tortrix

The Cherry bark tortrix is a pest on trees and shrubs of the rose family (Rosaceae). This means most common fruit trees have the potential to be affected including apple, cherry, plum, and peach. It’s a relatively new pest to Washington state having arrived here in the early 90’s. Damage is caused by the larvae of the moth Enarmonia formosana. Eggs are laid singly by adult moths on the bark of susceptible species. After hatching they burrow through the bark and begin to eat the cambium. This damage to the part of the tree that transports water and nutrients decreases the tree’s vigor. Decreased vigor and the wounds caused by the larva can make the tree more susceptible to other diseases or fungi. An excellent indication of whether there’s an infestation in a particular tree are frass tubes and (to a lesser extent) frass, which are small pellets of insect excrement- see photos.

A few individual frass tubes can be seen at the base of this cherry.

A few individual frass tubes can be seen at the base of this cherry.

Control options are limited. It’s only practical to attempt to control the insect in its larval stage as the flying time for the moth can extend from April to September. Cherry bark tortrix (CBT) prefer to attack stressed or damaged trees and also appear to attack Mount Fuji Oriental and Weeping (or Higan) Flowering cherries especially hard. Some things that can be done to help control this pest are to conserve parasitic wasps and other predators by reducing or eliminating pesticide usage and avoiding any mechanical injuries or large pruning cuts, as this provides easy access into the tree. There are a number of parasitic wasps that will parasitize CBT eggs and larvae. So it stands to reason that growing plants nearby that benefit these wasps will help control CBT. These parasitoid wasps prefer plants that have small flowers and are rich in nectar such as dill, yarrow, mustard, fennel- umbels and asters in general.

A relatively unusual sighting of the larvae of cherry bark tortrix. Take note of all the frass pellets.  I took this photo in North Seattle in late May.  The larvae are about 1cm in length.

A relatively unusual sighting of the larvae of cherry bark tortrix. Take note of all the frass pellets. I took this photo in North Seattle in late May. The larvae are about 1cm in length.


Trees may be able to survive for years with small infestations and eventually overcome them. When infestation is first noticed, remove any loose bark and cocoons in the spring, and remove and destroy heavily infested branches or trees. Pheromone traps are available for monitoring CBT and may also provide some control if deployed in sufficient numbers. There are a few approved pesticides for the homeowner, but they are only approved for use on ornamental trees. See the WSU hortsense website for more information.
 
 
 
 

Sources:
http://pep.wsu.edu/hortsense/ found under- tree fruits; cherry.
http://jenny.tfrec.wsu.edu/opm/displaySpecies.php?pn=570
http://puyallup.wsu.edu/plantclinic/resources/pdf/pls67cherrybarktortrix.pdf
http://www.seattle.gov/util/groups/public/@spu/@conservation/documents/webcontent/COS_005341.pdf
Edible Forest Gardens Vol. 2 D. Jacke and E. Toensmeier. pg 579

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