April 26, 2006

Christmas Tree Scouting Report Number 7 - April 26, 2006
Weekly newsletter compiled by Sandy Gardosik, PA Department of Agriculture.


Spruce spider mites were active on Fraser and Canaan fir in Columbia, Juniata, and York counties this week. This mite was also found damaging Concolor fir in Columbia County. Spruce spider mite is not as common on Concolor fir as it is on the other species of firs grown as Christmas trees. Control your mite populations now before the new growth emerges. If there was any damage to the previous year's growth, controlling mites now will protect the new growth and hide mite damage from previous years.

Douglas fir needle midge adults have begun to emerge from their overwintering sites beneath Douglas fir trees in Bucks County. This midge is about 3mm long and has an orange abdomen and long legs and antennae. The males' abdomens have blunt posteriors, and the females have long ovipositors used for egg laying. Adults mate soon after emerging, and females begin egg laying within a couple of days following mating. Eggs are laid on and between the bud scales or needles and are elongate, colored orange with a red spot in the center. These eggs will hatch within a few days after being laid and the larvae will immediately enter the new, expanding needles and begin forming a gall where they will continue feeding and growing until fall.

Trees of Douglas fir are near 10% bud break in Bucks, Dauphin and York counties and growers should apply their first spray for Rhabdocline needle cast within the next couple of days. In Juniata and Northumberland counties, trees were just beginning to break bud late last week. In Columbia County, only the small trees were beginning to show green tips. On a warm, dry afternoon, Rhabdocline needle cast may look as though the lesions are not mature. All it takes is a little dew in the mornings to cause the disease organism to rupture the epidermis of the infected needle and expose the infectious orange spores. You can test this by removing a few needles with Rhabdocline and placing them in water for about 10 minutes. The infected lesions on the undersides of needles will rupture and expose the orange spores.

When I returned to York County this week to check on the percentage of balsam twig aphid egg hatch, I could not find any of the "stem mothers" feeding on the needles. I examined the new cones on the trees and had no trouble finding them between the cone scales. As bud break begins, the overwintering "stem mothers" produce offspring rapidly, and these nymphs damage the new, expanding needles. The time to control this aphid is before bud break, but after all overwintering eggs have hatched.

A fairly high population of pine needle scale was found on Scotch and white pine in Lancaster County. This scale can be found on all species of Christmas trees, but prefers pines. The shape of the white armor covering sometimes varies a bit to fit the width of the host needle. This scale overwinters as tiny red eggs underneath the dead female's cover. The best time to control this scale is after eggs hatch and the tiny red crawlers are exposed on the needles. Look for the first generation in mid-May and the second in mid-July.

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.