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June 25, 2008

Christmas Tree Scouting Report #14

This report is compiled by Sarah Pickel of the PA Department of Agriculture from the scouting recordings of Jim Fogarty and Kyle Halabura of Halabura Tree Farms, Susan Newhart of Arcadia Trees in Susquehanna County and Sandy Gardosik, Karen Najda, and Cathy Thomas of the PA Department of Agriculture.

This will be the last regular scouting report of the 2008 growing season.  There will be a special report sent out the first week of August regarding the 2nd generation of Cryptomeria scale. 

Yesterday in Schuylkill County, at 850 Growing Degree Days, eggs and crawlers of Cryptomeria Scale were still present on Fraser and Canaan firs.  Several growers had applied their first insecticide application for this pest last week, and had good control of the first wave of crawlers.  Eggs that were still under the adult scale coverings during the first application remained viable and continued to emerge.  A 2nd spray applied 7 – 10 days after the first application is recommended to control further emergence of crawlers.  Later in the summer, around the last week of July into the beginning of August, the second generation of Cryptomeria eggs will begin to hatch.    

In Adams County, crawlers of Elongate Hemlock Scale (EHS) were found on the new growth of Grand and Fraser fir.  Because the life cycle timing is varied for EHS, the recommended control for EHS extends for a period 12 weeks.  This can be done by making 3 sprays, 4 weeks apart or 4 sprays, 3 weeks apart.  According to research done by Penn State, dimethoate, or other chemicals with trans-laminar properties, will work best.

Cryptomeria and Elongate Hemlock Scales are both located on the lower branches of the trees, so penetration of chemicals into the inner portion of the tree is very important.  Recently mowed rows will help to ensure that proper coverage is achieved.

Crawlers of Striped Pine Scale were observed on Scotch pine in Adams County this week.  This soft scale feeds on the bark of Scotch and Austrian pine trees.  Adults of this pest have a ¼ in, domed scale covering that has a tortoise shell appearance with beige stripes. Crawlers for this pest are orange to brown.  Insecticide applications can be made at this time, with a 2nd spray following a week later.  Another option for control is horticultural oil applied to the overwintering stage of the scale, which will be present in the fall.

Growers in Schuylkill County sprayed for crawlers of Fletcher scale on Arborvitae this week.  One of the noticeable symptoms of this scale is black sooty mold which forms on the foliage from the honeydew produced by the scale.  Spray treatment for this scale can be applied now, while the crawlers are present.  Repeat applications may be necessary.  Another option is horticultural oil applied during the dormant season.

Some of the pests that growers can be thinking about treating in the fall would be spruce spider mites and eriophyid mites.  These are cool season mites and will become active again in the late summer or early fall.  Spider mites cause a yellowing on the lower portion of the needles closest to the twig.  Eriophyids can be found on spruce and cause a bronzing or bleaching effect to the needles.  Two sprays of registered miticides, 7 – 10 days apart will be effective for the treatment of these mites.  Remember that not all miticides are effective on Eriophyids.  Avid, Dimethoate, Envidor or Sevin will work on Eriophyid mites.  Oils can also be used on both mites, but will remove the bloom on the needles of Blue spruce.

Cooley spruce gall adelgids and Easter spruce gall adelgids can also be controlled in early fall.  The overwintering nymphs of the spruce adelgids will be found on twigs at this time, where they will be unprotected by the waxy coatings of mature nymphs.  Cooleys will be found on Colorado blue spruce or Douglas fir and Eastern spruce gall will be found on Norway spruce.  Dormant oil can be used for control on Norway spruce or Douglas fir, but again growers will want to avoid using oil on Blue spruce to prevent the loss of the blue bloom.

Last week, crawlers of Elongate Hemlock Scale were seen in Adams and York Counties.  A spay series lasting 12 weeks is recommended.  This may consist of 3 sprays, 4 weeks apart or 4 sprays, 3 weeks apart.  Penn State research recommends using Dimethoate.  Other chemicals with trans-laminar abilities will also work.  Hosts of this scale are true firs, Douglas fir, hemlock and spruces.  Damage caused by this scale can also be found on lower tree branches and resembles cryptomeria damage, but can have a white cast in heavy cases. This white appearance comes from the shedding of the male scales’ white waxy covering.

Because Cryptomeria and Elongate Hemlock Scales are located on the lower branches of the trees, whatever pesticide growers choose to use, they should be directed toward the lower portion of the tree and at the underside of the branches.  Recently mowed rows will help to ensure that proper coverage is achieved.

Last week Bagworm larvae were seen feeding on Douglas fir and Arborvitae in Dauphin and Schuylkill Counties.  Bagworms can infest any conifer species.  Growers can still spray for this pest if they did not get to it last week.  Only one spray may be necessary for bagworms.  If control is not achieved at this point in the season, growers can hand pick the bags that these larvae form later in the season. Just make sure to remove them from the field.

For growers who also grow Arborvitae, juniper, cypress, yew or hemlock, another pest to be scouting for is Fletcher scale. This soft scale can cause black sooty mold to form on the foliage thanks to the honeydew they secrete.  In Schuylkill County, crawlers were found under the adult scale coverings on Arborvitae.  These nymphs should be emerging sometime this week or next.  A registered insecticide can be used against this crawler stage.

Many growers may be beginning to shear their trees this week, usually starting with pine species.  It may be a good thing for employees to keep a note book close by to record any pest problems they see while they’re out shearing.  While it may be too late to treat for many of the pests this season, often a fall treatment is possible.  Employees could be recording useful information about pests that can be dealt with in the fall.