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May 7, 2008

Christmas Tree Scouting Report #7 - May 7, 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, 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.

In Schuylkill County, some growers will be applying their second fungicide spray on Douglas fir for Rhabdocline Needlecast either the end of this week or the beginning of next week. In last week’s report, I discussed the 3-4 spray schedule recommended as the control program for Rhabdocline Needlecast. The spray program is the same for Swiss Needlecast, only in this program, the 4th spray is not seen as optional, since the sporulation period for Swiss Needlecast is longer than that of Rhabdocline.  Swiss Needlecast can be distinguished by rows of black fruiting bodies on the underside of Douglas fir needles. The tips of the needles or the whole needles may be yellow or brown.  The life cycle of Swiss Needlecast is similar to Rhabdocline, except for the fact that infected needles are not always shed after one season. These needles can remain on the branches for two or three seasons and continue to be viable until they are cast.

In Adams and Dauphin Counties, Cooley Spruce Gall Adelgids have begun to hatch and the nymphs have moved onto the tender needles of the newly opened buds on Douglas Fir. At this point in the season, chemical control is not feasible.  The nymphs are protected in the needle clusters and have started to feed on the needles. This feeding is what causes the Douglas needles to appear kinked or distorted. On Colorado blue spruce, as the new buds expand, the nymphs will begin to feed at the needle bases of the new bud which will produce galls on the shoots. The time to control this pest is in the fall or early spring before overwintering nymphs produce a covering of wax.    

On Norway spruce, galls caused by the Eastern spruce gall adelgid are beginning to form at the base of the new buds. The life cycle of this pest is very similar to the Cooleys’. The nymphs will be protected in the gall until they emerge in the late summer/early fall as adults. They will then reproduce. Treatment for this pest is also best during the early spring or the fall (after galls have opened). 

In Schuylkill County, Douglas fir needle midge adults have been observed. This small, orange fly-like insect has a very small window of control. Their emergence coincides with Douglas fir bud break and they soon begin to lay eggs. The main symptom is distorted, kinked needles that will turn yellow and then brown. When trees are beyond 10% bud break, control is too late for this season. If treatment was missed this year, growers should monitor their trees for symptoms and then be ready to apply spray treatments before bud break next year.

In Adams and Schuylkill Counties, growers have reported fewer weevils trapped this week. If some growers have been monitoring and have not yet caught any weevils, they should be monitoring their trees for feeding damage, which will appear as small holes in the leaders, often covered by a bubble of glistening sap. If weevils are still present, they will be laying eggs in the leaders by this point in the season. Once the eggs are present in the leaders, chemical control is no longer worthwhile for the season.