April 11, 2003

Christmas Tree Scouting Report -
Number 3

Welcome to the Christmas Tree Scouting Report for the week ending April 11th. The next report will be available after 4 PM on Friday April 18. To receive a FAX of this week's message, please call (814) 865-1636. To report pest activity at your location or request email report, please call 717 772-5229. 

As you all know, this was a poor week for fieldwork. Thursday was the only dry day and we did see some sunshine for a few hours. But, fields remained wet and planting operations are well behind schedule on most farms. Spray operations are also suffering from the rain and snow and soggy fields.

White pine weevil traps in Perry County had 3 Pales weevils but there were not any white pine weevils collected. As you may recall, this regular trapping site has a tremendous population of white pine weevils so the lack of weevils in the traps was not due to a low population. The Pales weevils may have been trapped before the snow and cold temperatures on Monday. A grower who is monitoring his field with Tedders traps began catching white pine weevils the last week in March and has already sprayed the tops of his trees. But with the slow down in accumulation of Growing Degree Days, we may see a longer emergence period, and more sprays will be required to control white pine weevil and possibly other pests.

Even with this cool weather the balsam twig aphids are about 50% hatched in Adams and York counties. They are feeding on the underside of needles. This feeding by the 1st generation nymphs on last year's needles does not cause damage. By bud break these nymphs will have matured into females and will produce offspring rapidly. These 2nd generation nymphs will feed on the new growth and that will cause damage. Needles will be curled and stunted and may be covered with sooty mold due to the honeydew secreted by the aphids. The optimum time to control this pest is right before bud break when most of the overwintering eggs have hatched. There is still time to check your own fields for this pest and plan your control.

Pine bark adelgids are starting to deposit eggs on the bark of eastern white pine in Adams County. These adelgids are generally not serious pests unless the population is extremely high. Only then should treatment be necessary. We have noticed lady beetles feeding on these adelgids over the last few years and some control appears to occur naturally.

Spruce spider mite eggs were observed in Adams County this week but none have hatched. You can scout for mites by using a hand lens to look for mites or eggs or you can examine last year's needles for symptoms of mite feeding. When spider mites feed on the needles, they withdraw cell contents, including chlorophyll. The pattern of discoloration is called "stippling". The damage if frequently confined to the base of needles, and in the field, this may appear as a yellow strip on either side of the twig. As populations increase the "stippling" will extend over entire needle and premature needle drop may result. Look for damage about halfway up the canopy and in the interior part of the tree.

Elongate hemlock scale was found on fir this week in York county. The overwintering eggs and adult females were present but we did not see any evidence of any crawler emerging in 2003. In warmer springs crawlers can be found very early in the season. This particular scale pest, because of its unsynchronized life cycle and the female scale's unusual protective covering, is very hard to control. Multiple sprays throughout the growing season are necessary to kill exposed crawlers and early instar nymphs.

A new pest of Douglas fir has been confirmed from Pennsylvania. The Douglas-fir needle midge was collected at three sites in fall of 2002. One site in Northumberland County has a moderate population but at one of the two Lehigh County sites, the population is fairly high. At this time of year, needles damaged by the midge's gall creating habit have reddish brown patches. These discolored areas may initially resemble infection sites of rhabdocline needlecast. All Douglas fir growers are encouraged to take a closer look at their rhabdocline to confirm that it is indeed a disease, and not this new insect pest. A pest alert with pictures and information on life cycle can be found at the Penn State Christmas Tree web page at If you think you have this pest, please contact Rayanne Lehman at 717 772-5229.

In Westmoreland County, Mike Masiuk reports that European pine sawfly eggs are swollen in the needles and ready to hatch as soon as warmer temperatures arrive. Cooley adelgids are covering with white waxy threads and the control window is starting to close in his part of the state.

The next report will be available after 4 PM on April 18th, 2003.