May 28, 2008

Christmas Tree Scouting Report #10 - May 28, 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; Jim Fogarty and Kyle Halabura of Halabura Tree Farms; and Sandy Gardosik, Karen Najda, and Cathy Thomas of the PA Department of Agriculture.

No Cryptomeria scale eggs were found yet in Northampton, Schuylkill or York Counties. Egg laying should be happening soon though. To monitor for the life stages of this scale, first look for damage from past seasons’ scale population. This will be found on lower branches of mainly fir and hemlock trees. The upper side of the damaged needles will have a chlorotic (or yellowed) mottled appearance.  On the undersides of the needles, this covered scale resembles a sunny-side up egg, with a mostly white covering with a yellow center.  To look for eggs, flip this scale cover with a pin and use a hand lens to see the oblong yellow eggs which will be surrounding the round, flat female scale. Or a simpler method would be to put a white sheet of paper or paper plate into the tree and tap the branches. This will dislodge the eggs onto the plate and they’ll be visible with the hand lens. The eggs should be present within the next week, followed two weeks later by the hatched crawlers. Targeting the crawler stage is critical to achieving good control, so monitoring your scale stages is very important.

On Douglas Fir in Adams County, Cooley Spruce Gall Adelgids have laid a second generation of eggs.  These eggs will likely hatch in mid June.  Chemical control is not recommended at this stage in the season for two reasons: 1) the worst of the feeding damage has already happened to the new growth and 2) beneficial predator insects such as lady beetles and green lacewings are present at this time and will be killed by an insecticide spray.  In the fall, Cooleys will lay eggs which hatch into the over-wintering nymphs sometime in October.  Chemical control can be applied at that time, or in the early spring, before the over-wintering nymphs mature.  However, if populations are very high now, a pesticide treatment could be applied later in June after the eggs have hatched, but before the adelgids have waxed over again. 

In Northampton County, growers are dealing with a high population of the Admes mite on Colorado blue spruce.  This mite is larger than the spruce spider mite and has a dark red body with tan legs.  The life cycle of the Admes mite is similar to the spruce spider mite.  A symptom of damage is a stippling or bleaching of the needles, which when heavy, can turn brown and even drop.  Treatment calls for application of a miticide twice, 7 – 10 days apart.

In Adams and Cumberland Counties, the Balsam Twig Aphids are still active.  At this time in the season, growers may see lady beetles congregating on the new growth of true firs.  The lady beetles will be feeding on the aphids.  This feeding may be enough to keep aphid populations in check for the rest of the season.  

Growers in Schuylkill County are getting ready to apply their third fungicide spray for Rhabdocline needle cast.  Remember that if wet conditions persist after the 3rd spray, or if growers are also treating for Swiss Needlecast, a 4th spray two to three weeks after the 3rd could be made.