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May 3, 2006

Christmas Tree Scouting Report Number 8 - May 3, 2006
Weekly newsletter compiled by Sandy Gardosik, PA Department of Agriculture.

Growers in Berks, Bucks, Juniata and Schuylkill counties applied their first spray for Rhabdocline needlecast this week. The second spray should follow one week after the first, and a third application made two weeks after the second spray application.

Growers who are planning to spray for spruce needle rust on Colorado blue spruce and Serbian spruce need to follow the same spray schedule as for Rhabdocline needlecast on Douglas fir. Spruce needle rust was first detected in Luzerne County in 1991 and has now been found in most eastern PA. Counties.

In Perry County, trap counts of adult white pine weevils declined this week, and eggs were found in white pine terminals. Adult weevils were found feeding on Serbian spruce terminals in Schuylkill Co., where eggs were found, also. Although eggs were found in both counties, no larvae have been observed as of this week. The only way chemical controls could be effective after egg hatch would be with a chemical that has translaminer properties (can be absorbed through the bark). Research on managing the control of the white pine weevil through Penn State and the IPM program at the Pennsylvania Department of Agriculture over the next few years will hopefully find the best control strategy for this statewide pest. 

Pine spittlebugs are beginning to hatch and the frothy, white spittle masses produced from partially digested sap are apparent on white pine and Douglas fir in Bucks County.  This insect feeds on all species of Christmas trees but seldom does harm unless it is very abundant.  However, wounds produced by their feeding can create a pathway for Diplodia shoot blight (Sphaeropsis) to invade. If signs of branch dieback or Diplodia become present in late summer, control of this pest may be necessary next spring.

In Perry County feeding activity on the new growth on Norway spruce by the adults and newly hatched nymphs of the Eastern spruce gall adelgids are beginning to cause early gall formation. Once galls begin to form, control can only be achieved by removing the green-colored galls on spruce in early summer before these galls mature.  On Douglas fir, adults and eggs of the Cooley spruce gall adelgids can be found covered with masses of long waxy fibers that look like tiny cotton balls on the undersides of previous years' needles. These eggs are beginning to hatch and tiny black nymphs will migrate to new growth where they can be found feeding on the new, expanding needles. Feeding damage on Douglas fir may cause needle distortion, discoloration at feeding site, and premature needle drop. To control Eastern spruce gall adelgids on Norway spruce, and Cooley spruce gall adelgids on both Colorado blue spruce and Douglas fir apply a registered insecticide in early fall or early spring when the adelgids are immature.

To prevent damage to new growth of true firs by balsam twig aphids, apply chemical controls to trees that were damaged last year before the buds break. At bud break, mature aphids produce live offspring rapidly and these nymphs feed on and distort new growth. When aphid colonies build, so do numbers of natural enemies such as ladybird beetles, green lacewings, and flower flies. If an insecticide treatment is applied at this time, damage is already done to the new growth, and the natural predators are killed.

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