June 7, 2006

Christmas Tree Scouting Report Number 13 - June 7, 2006
Weekly newsletter compiled by Sandy Gardosik, PA Department of Agriculture.

Damage from the white pine weevil is becoming evident on Norway spruce in Schuylkill County and on white pine in Dauphin and Lebanon counties. Now is the time to keep an eye out for dwarfed or wilting terminal leaders turning brown. Removing material damaged by the white pine weevil now can save you from losing two or three years top growth.  Prune out all infested material, remove from field and destroy by burning. Train a new leader by cutting back all but one live lateral shoot by at least half their length to maintain single-stem dominance.

No cryptomeria scale crawlers were found on Fraser fir in Dauphin, Lebanon and York counties, or on Concolor fir in York and Canaan fir in Lancaster. I expect to see egg hatch in the next week.

Adult females of the balsam twig aphid (BTA) are beginning to lay their overwinter eggs on the stems of Canaan fir in Adams County. When first laid, the overwinter eggs are light in color and will darken as they age. If you see signs of damage from the BTA, such as curled new growth, take note and apply your sprays before bud break next spring. Trees will grow out of twig aphid damage as the shoots are elongating if the damage is not too severe.

Spruce spider mites are beginning to move to the new growth of Canaan fir in Adams, Lancaster and Schuylkill counties. This year's spring temperatures have been ideal to help mite populations to build up to damaging levels. Remember to apply a second spray application 7 to 10 days apart for best control unless the label states otherwise.

On Scotch pine in Adams County crawlers of the striped pine scale were found underneath the adult female when they were removed. No crawlers were found in Dauphin County. To control this soft scale, wait until all eggs have hatched and crawlers have moved out from underneath the adult female's body.

Rhabdocline needle cast was still sporulating on Douglas fir in Adams County when infected needles were placed in water to check for viability. In Dauphin County infectious lesions were beginning to dry and turn black, indicating fungus was no longer infectious. To control Swiss needle cast in your Douglas fir plantations, a fourth spray is necessary, since Swiss needle cast sporulates longer than Rhabdocline needle cast.

Eriophyid mites are causing damage to 2005 needles on Norway spruce in York County. This eriophyid mite is also known as a "rust mite" for good reason; its damage causes the needles to turn a rusty brown color. Control this mite with two application of a registered insecticide 7 to 10 days apart.

Light damage from frost has been noticed in some fields in Adams, Lancaster, Lebanon and York counties.  In Lebanon and York counties frost has damaged the buds of Douglas fir and Concolor fir on one side of the tree leaving only one half of the tree with new growth. In Lancaster County new growth of Douglas fir can be found dead and dry. We suspect frost may be the reason for damage to the new growth on Norway spruce in Adams and York counties.  

If you have any pest information to report, please email Sandy Gardosik at 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.