Plant & Insect Diagnostic Clinic Update - May 20, 2009

The Clinic has received the following samples in the past two weeks:


NOW is the time to be checking Scot, Mugho and Austrian pine trees for needle feeding damage by the larvae of the European pine sawfly. Pine sawfly larvae (photo below) can be present any time after mid-May. Defoliation lasts for four to five weeks and usually peaks near the end of May. Damage is highly variable from tree to tree and from branch to branch within the same tree. Controls can be handpicking, pruning or spraying with a contact insecticide. Read and follow label directions.  More in Horticulture and Home Pest News, May 19, 2000

The clinic has been receiving samples of oystershell scales.  These scales infest a wide variety of woody plants.  The scales can be hard to see since they are close to the same color as the bark, but if you get up close you can see the individual scales.  Overwintering eggs are or will be hatching soon, so prune out heavily infested branches and treat with an insecticide labeled for scales on ornamentals. 

Carpenter ants continue to march up and down out kitchen counters.  Remember that carpenter ants do not eat wood; this is why we see them in our kitchens eating food.  Carpenter ants hollow out water damaged wood for their colonies. 

Diseases and Disorders

Conifers (click name for link to more information)

  • Environmental damage to concolor fir; Related winter desiccation or poor drainage on heavy clay soils.
  • Winter desiccation to arborvitae and pines (white pine)
  • Phytophthora root rot on arborvitae young plants. 
  • Phomopsis tip blight on juniper 
  • Rhizosphaera needle cast of blue spruce
  • Sudden needle drop (SNEED) on blue spruce
  • Botryosphaeria canker on red cedar 



Mushroom Identification

European pine sawfly larvae.  Note feeding damage to old needles to left.  Photo by Steven Katovich, USDA Forest Service, European pine sawfly larvae. Note feeding damage to old needles to left. Photo by Steven Katovich, USDA Forest Service,


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