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Spruce spider mites

During examination of white spruce branches for spruce budworm on May 19th , numerous specimens of spruce spider mites were discovered on the new shoots. The spruce spider mite, Oligonychus ununquis, can be a serious problem in windbreak and other landscape conifers.  Most conifer leaf mites overwinter as eggs under the bud scales and can produce three or more generations per year.  They usually prefer the older needles.  Damage to needles occurs by adult mites sucking plant juices causing tissues to rupture and dry up.  Branches appear grayish due to the mottled needles.  The webs, formed during extensive feeding, collect dirt and dust on the foliage; this might be your first clue to a mite infestation.  Warm, dry periods followed by moist, cool conditions favor the buildup of large populations of spider mites.  Reproduction drops off during the summer months, so there is usually a fall and spring defoliation cycle to cause concern.  Many pesticides are available for control of mites.  Horticultural oils applied two to three times during the early spring or late fall, seven to ten days apart are recommended to control mite populations.

Spruce budworm degree days 

OOPS!  Let's try this again.  The table in the last Newsletter was in degrees Celsius rather than degrees Fahrenheit.  The author claims ?temporary mislocation?, apparently he was confused about which side of the Canadian border he was on.  Here's the corrected version.
 
Accumulated spruce budworm degree days
Peak stages of insect developmentBalsam firWhite spruce
2nd instar192 F197F
3rd instar226217
4th instar309280
5th instar399366
6th instar563492
Pupae775698
Adult872818
Base temperature = 46 F.
Starting date = March 1.