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May 21, 2008

Christmas Tree Scouting Report #9 - May 21, 2008

This report is compiled by Sarah Pickel of the PA Department of Agriculture from the scouting recordings of Ann Echard of Penn State University, Jim Fogarty and Kyle Halabura of Halabura Tree Farms, Susan Newhart of Arcadia Trees in Susquehanna County, and Cathy Thomas of the PA Department of Agriculture.

As the new growth of firs such as Canaan and Concolor expands, growers may be seeing a distortion or twisting of the needles associated with Balsam twig aphid.  While Frasier is the most common host to this pest, all true firs are susceptible.  On Concolor fir, the needles may naturally correct themselves of this twisting as they grow throughout the season.  At this point in the season, chemical treatment for balsam twig aphid is not recommended unless populations are at very high levels.  It is too late to prevent the curling of needles once feeding on the new growth has begun.  Also, any insecticides sprayed now will be damaging to the beneficial insect populations. 

In York County, no eggs were found of the Cryptomeria scale yet.  Growers who are scouting could expect to see them in the next week or two.  The eggs will be visible with a hand lens.  Simply remove the white scale covers with a pin or fingernail and look for yellow eggs around the yellow adult female scale.   Within two weeks or less of egg laying, crawlers will begin to emerge.  This is the stage when growers will begin their control sprays, so stay tuned.   

Pine Needle Scale crawlers continue to emerge in Adams and Schuylkill Counties.  These reddish two yellow crawlers will settle and begin to form the waxy white covering.  If this pest is in high populations, insecticide treatment can be applied at this time before the crawlers for their covering. 

In Schuylkill County, growers are reporting the sporulation of Spruce Needle Rust on Colorado blue spruce and Serbian spruce.  Colorado blue spruce are the most common host trees in Pennsylvania. Growers who have a problem with this rust should have applied their first fungicide treatment at 10 percent spruce bud break.  A second spray is recommended a week later, followed by a third three weeks after the first spray.

Some growers in Schuylkill County are seeing very high numbers of Eriophyid mites.  For control of this mite, not all of the common miticides that are used on Spruce spider mites are effective for Eriophyid mites.  Using a product specifically labeled for Eriophyid mites should give good control.  Some currently available to Pennsylvania growers are Avid, Envidor, Sevin & Judo.

In Susquehanna County, Cooley spruce gall adelgid and Eastern Spruce gall adelgid are found to be waxed over.  In Adams County, the galls caused by Cooley spruce gall adelgid have begun to develop on Colorado blue spruce.  One form of mechanical control for this pest and the Eastern spruce gall adelgid is to prune these galls from the tree and remove them from the field so as to prevent the late summer release of the adult adelgids from the galls.