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April 30, 2008

Christmas Tree Scouting Report #6 - April 30, 2008

This report is compiled by Sarah Pickel of the PA Department of Agriculture from the scouting recordings of Tim Abbey of Penn State’s York County Cooperative Extension, Ann Echard of Penn State University, Jim Fogarty and Kyle Halabura of Halabura Tree Farm in Schuylkill County, Sandy Gardosik of the PA Department of Agriculture, Gerald Nesvold of Tannenbaum Enterprises in Schuylkill County, Susan Newhart of Arcadia Trees in Indiana County, Mel Nye of American Green Corporation in Schuylkill County and Cathy Thomas of the PA Department of Agriculture.

All reporting scouts are seeing Douglas fir bud break in their fields.  In the southern counties of Adams and York, bud break is at 90 – 100%.  In Schuylkill County, growers are reporting bud break of 25 – 50 % for Douglas.  Growers in Schuylkill County have applied their first sprays for Rhabdocline Needlecast this week.  Rhabdocline is a fungal disease which affects only Douglas fir and causes the loss of the previous season’s needles.  The symptoms are reddish-brown spots on the needles.  As the fungus matures in the spring, the infected areas swell to form fruiting bodies.  These swollen areas will be ready to rupture and release spores just as the Douglas fir are beginning to break bud.  All that’s required to trigger the release of the spores is moisture.  With a bit of damp weather, the spores will be carried by the wind to the newly growing needles.  To prevent infection, experts recommend that a fungicide be applied at 10% bud break.  Growers can follow-up this first spray with a 2nd spray one week later and then a 3rd spray two weeks later.  If it is a wet spring, or growers are also treating for Swiss Needlecast, a 4th spray can be applied two to three weeks after the 3rd.  In Dauphin County, Rhabdocline lesions have already begun to rupture.

Also on Douglas fir, in Adams, Dauphin and York Counties, Cooley Spruce Gall Adelgids are laying eggs under their protective wax coverings.  In Dauphin County, some eggs have begun to hatch and the nymphs have moved onto the tender needles of the newly opened buds.  In York County, Cooley’s are also laying eggs on Colorado blue spruce.  In Adams County, on Norway spruce, Eastern Spruce Gall Adelgids have laid their eggs also.

Bud break has also been reported on Concolor fir and Norway spruce in Adams and Schuylkill Counties.  Buds of Frasier fir are still tight, but balsam twig aphids can affect any of the true firs, so as fir buds begin to break, stem mothers of balsam twig aphid will begin to give birth to live young.  The young will move into the buds and begin feeding on the new needles, which will cause the typical curling needle symptom.      

In Adams, Schuylkill and York Counties, the numbers of white pine weevils caught in traps this week have been down, but feeding damage has been noted.  No scouts have reported finding eggs yet.  If growers are scouting their fields and looking for damage, they can look for a glistening sap bubble as an indication of damage.  Using a knife to scrape the bark away at the site of weevil feeding, growers can check to see if eggs have been laid.  Eggs will be oblong and milky white.

Spruce spider mite and Eriophyid mites are continuing to hatch in Adams, Dauphin, Schuylkill, and York Counties.  These are both considered cool season mites, so as seasonal temperatures increase, populations will decrease, but while the cool temperatures we’ve been experiencing remain, these mites can continue to cause damage.  Some growers in Schuylkill and York Counties are reporting that they are seeing higher than usual numbers for Eriophyid mites.  This could be because no control treatments were made last season, because the climate conditions are favoring this mite, or possibly because the population cycle is on an upswing.    

When growers are out in their fields, they may be seeing a few minor pests emerging at this time.  I have seen the following two pests out in Schuylkill County.  The European sawfly is mainly a pest of Scotch pine, but can affect Eastern white pine.  These black-headed larva feed in clusters on pine branches.  As young larva, they can only nibble on the needles, so needles appear thin and straw like, but as adults, they can strip a branch of its needles.  Another minor pest is the pine spittle bug.  This bug can be found on any species and is most noted for surrounding itself in a protective spittlemass.  These bugs can cause branch tip flagging and can also be noted for making trees more susceptible to fungal blight.