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April 22, 2008

Christmas Tree Scouting Report #5 - April 22, 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, Steve Derstine of J.C. Hill Tree Farm in Schuylkill County, Ann Echard of Penn State University, Jim Fogarty and Kyle Halabura of Halabura Tree Farm in Schuylkill County, Galen May of Pine View Farm in Franklin County, Gerald Nesvold of Tannenbaum Enterprises in Schuylkill County, Susan Newhart of Arcadia Trees in Indiana County and Cathy Thomas of the PA Department of Agriculture.

In some locations in central York County, bud break is beginning on Douglas fir. Also, bud break has been reported on pot-grown Douglas fir in Schuylkill County. Pot-in-pot trees are likely to break bud earlier than ground-planted trees, but bud break for other trees will not be far behind. In many areas, cones have been developing this week. Sometimes if viewed from afar, this development can be confused with bud break.

Last week, balsam twig aphids were hatching in Adams and York Counties. These newly hatched stem mothers have been feeding and molting while preparing to give birth to the new live young that can get into the swelling tree buds and feed on the developing needle tissue. As soon as the buds open up, the new nymphs will move inside and begin feeding under the protective bud sheath. When this happens, insecticide sprays will not be effective to prevent needle damage. Nymphs can also feed on the developing cones. There, too, they will be protected from insecticide sprays, so to be effective, insecticide sprays should be applied soon before the new aphids are born.

White Pine Weevils were still found in Bedford, Schuylkill and York Counties this week. Growers in Schuylkill County have already applied an insecticide for control of the weevil. The Growing Degree Day (GDD) tally in central Schuylkill County is 99. In Susquehanna County, they’ve accumulated 57 GDD. The range of the white pine weevil is 7 – 58 GDD, so they should have emerged in most PA locations. If growers are not finding weevils in their traps, they can look to find weevils on the leaders of white pine, Serbian spruce, Colorado blue spruce, Norway spruce or Douglas Fir. At some locations, the numbers of weevils trapped this year have been lower than those in past years, so if growers who have had weevil problems in previous years are not finding them this year, the pest population could simply be at a low point. 

In Adams, Franklin, Schuylkill and York counties, spruce spider mites are hatching. At this point in the season, before bud break, growers could apply horticultural oil to control all stages of spruce spider mite.  Savey and Hexygon, which are different trade names of the same product, are also effective on all stages of spider mite.  In the spring, mite populations are in the old growth of the tree, so control sprays must reach the interior of the trees.

Growers who have had damage from Douglas Fir Needle Midge in the past may want to consider applying a long-residual chemical before bud break to achieve the best control for this pest.  Last Fall or Winter, Damage from this pest would have caused needles to appear bent or kinked and turn yellow or brown.  Needle drop can also occur. The adult midge will emerge just as the first buds are beginning to break. These small (3mm), orange fly-like insects will mate as soon as they emerge and will lay eggs within 2-3 days in between the bud scales and new needles. After the eggs are laid, chemical controls will be ineffective.  The larvae will hatch from the eggs and immediately bore into the new needles.  Appropriate chemical controls can be found on the Insecticide and Miticide sheet.

Finally, growers who have Rhabdocline needle cast should be applying their first fungicide spray when Douglas fir are at about 10% bud break. Since bud break is just beginning in York County and Schuylkill, growers should be watching for this. Rhabdocline lesions usually sporulate in wet conditions, but a morning dew can be wet enough to cause the lesions to burst.