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April 5, 2006

Christmas Tree Scouting Report Number 4 - April 5, 2006
Weekly newsletter compiled by Sandy Gardosik, PA Department of Agriculture.

The White pine weevil adults are showing up in pyramidal traps as far west as Bedford County and north to Columbia County. Many growers have begun to apply their first spray for the weevil. With the forsythia in bloom and the red maples flowering one can assume the weevils are active. Within the next two weeks female weevils will be laying eggs beneath the bark of the terminal leaders. For best control apply a registered pesticide to the top 1/3 of the tree before eggs are laid.

The overwintering eggs of the balsam twig aphid (BTA) are beginning to hatch on Canaan fir in York County.  The true firs are the most common hosts in Pennsylvania. Feeding by this aphid causes twisted distorted foliage on tender new growth. Aphids secrete honeydew when feeding and when populations are high, needles stick together and become covered with a sooty mold leaving the foliage black. With a hand lens, look for the tiny, oval eggs covered with minute silver wax rods on the bark of twigs. The adults that hatch from these eggs are called “stem mothers” and are tiny, soft-bodied insects that are covered with a bluish-gray wax powder.   The “stem mother” feeds on old growth and do not cause damage. When buds begin to break, the adult aphid gives live birth and it is these aphids that cause damage to the new growth. This pest’s life cycle is completed by mid-June, with the overwintering eggs being the only stage present until late March the following year.  It takes two years to cover up damage from this pest. Keeping this in mind, if trees are to be marketed in the next three years and damage was noted the previous year, applying a registered insecticide after most eggs hatch and before buds break is recommended for a quality tree.

No spruce spider mite eggs were hatched on Fraser fir in Chester or Lebanon counties this week. Egg hatch will probably be in the next couple weeks. If you had damage last year, begin scouting for tiny, red eggs on the undersides of twigs.

Now is a good time to scout for Douglas fir needle midge. This is a fairly new pest that was detected in 2002 on Douglas fir in Lehigh and Northumberland counties. Survey for the spread of this pest throughout the state was conducted and to date the heaviest populations are found in the southeastern counties. At this time of year look for brick red, kinked, swollen needles. This can be mistaken for Rhabdocline needle cast because of the same brick red needle color at this time of year but these needles will not be kinked or swollen. The Douglas fir needle midge overwinters beneath its host, Douglas fir. When buds begin to break the adult midge emerges from its overwintering site, mate and begin laying eggs between bud scales and on the new needles. Eggs hatch in a few days and larvae enter needles immediately and begin feeding causing gall formation. Spring of 2005 the adult midge began to emerge April 22nd at 208 growing degree days (GDD), in Bucks County. As of April 4th the same site monitored last year has a total reading of 104 GDD.

If you have any pest information to report please email or phone Sandy Gardosik at sgardosik@state.pa.us or (717) 772-0521 and give pest, host plant and county where observation was made and I will include this information in the next report.