Larval skin?

Asked July 31, 2017, 3:31 PM EDT

I live in Marion County east of Salem, and found these on the ground near my garden house. (see attached photo) Can you tell me what insect they are from?

Marion County Oregon insect identification

3 Responses

From the photo, it appears to be the cast larval casing of carpenterworm moths (Prionoxystus robiniae). The larvae feed on oak, birch, ash, black locust, elm, maple, willow, cottonwood, pecan, and less frequently fruit trees. Do you have any such trees near your garden house?

Washington State has a great site with additional information on the carpenterworm moth, here. As does the University of California, here.

You may consider removing infested limbs or, depending on the severity of the infestation, the entire tree, to prevent any damage from the tree falling over.

there is a large stump of a locust that was cut down 5 or 6 years ago...it continues to sprout. There is also a very large, old oak (100'x120' spread) near the garden house. The oak has always been very healthy...do I have reason to be concerned about it? Should I consult an arborist? In the photo, you can see a number of small dead branches. There are naturally always some, but maybe more this year...I'm not sure. Maybe I'm only noticing them because of your answer.

It's never a bad idea to consult with an arborist if you are concerned about your trees.

Otherwise, the first line of defense against infestation is to keep plants healthy. Proper care of trees and shrubs discourages many borer pests and helps infested plants survive. Good sap flow from healthy, vigorously growing trees, for example, defends the plant from damage by many borer pests. Good horticultural practices include:

  • Minimizing plant stress and stimulating growth by using proper watering and fertilization practices.
  • Avoiding injury to tree trunks from lawn mowers, weed trimmers or construction.
  • Promptly caring for wounded or broken plant parts using pruning or wound paint during all but the coldest months of the year.
  • Properly thinning and pruning during colder months.
  • Removing and destroying infested, dying or dead plants or plant parts, including fallen limbs.