Christmas Tree Scouting Report: April 24, 2025

Weekly newsletter compiled by Kelly Piccioni, Penn State Extension. This week's scouting data contributors: Kelly Piccioni (Penn State Extension), Jim Fogarty (Halabura Tree Farm), Don deMackiewicz, Sarah Pickel, and Cathy Thomas (PA Department of Agriculture).

Pest Information

The region experienced a range of temperatures, with daytime highs fluctuating between 50°F and 80°F. These warmer temperatures have accelerated the accumulation of Growing Degree Days (GDD), promoting pest development and increasing the urgency for scouting and early interventions. In particular, spider mites are the most active pest going into this week.

Bud break watch:  pay close attention to your different field blocks and note that they can be opening at different times, and preventive treatments for Swiss and Rhabdocline Needle Cast will start soon. Heat this week should force more buds to break and needles to spread. Those new needles need protection from spores that land on them, which will germinate when they get wet from rain or dew.

White Pine Weevil

Growers in Berks County had counts as high as four weevils in a trap at once. Signs of feeding on the leaders has also been observed, but there have not been high numbers of visible adults. Growers in Schuylkill County and York County have not caught many weevils in their traps and plan to wait to see more activity prior to spraying. To decide when it is best to spray for your trees, scout and see if you can observe feeding on the leaders of White Pine, Serbian Spruce, and Norway Spruce. New growth on White Pine is measuring between .5" and 2" in length and strong cone formation. 

Spruce Spider Mites

Every scouting team member has viewed Spruce Spider Mites as the most active pest in their fields. Fraser Fir buds are swelling, but growers in Schuylkill County are not seeing any swelling yet in Canaan Fir. Spruce are starting to swell and break throughout Berks, Schuylkill, and York Counties. Note that spruce have quite a bit of variance in the fields for bud break, even trees side by side can be at different stages.

Follow these tips to know when the timing is accurate to spray in your fields: Select 10–20 random trees per block, Examine 2–3 twigs per tree using a hand lens (10x), Record presence/absence of mites or feeding damage (bronzing, rusting), Threshold: Treat if 80% or more of twigs show mite presence.

Balsam Twig Aphid

Low numbers of stem mothers have been observed in Schuylkill and York counties. This hatch typically occurs within the range of 30-100 GDD. These aphids have hatched from the overwintering eggs and will feed on last season's needles. This feeding doesn't cause much damage, but when bud break of firs begins, these stem mothers will give birth to nymphs that will enter the opening buds and begin feeding on the newly expanding needles. This feeding will cause the needles to curl, and this damage is not reversible.

When scouting for the balsam twig aphid, a hand lens is necessary. The overwintering eggs will be found on the twigs, tucked in at the bases of needles. They will most commonly be found on the outer two inches of growth and on undamaged twigs located next to twigs with damage. The eggs are football-shaped and covered in fine silver filaments. The stem mothers that hatch from these eggs are pale green, wingless, and waxy.  They often will have a clear bubble of 'honey dew' or excrement at their posterior. If growers are having difficulty finding aphids on the foliage, an easy scouting technique is to hold a paper plate under symptomatic foliage and tap the foliage to dislodge any hatched aphids onto the plate.  A hand lens will be helpful to see aphids moving on the plate.

To prevent damage from this pest, growers who have had damage in the past should apply a horticultural oil or insecticide after most of the eggs have hatched, but before bud break.

Douglas Fir Needle Midge

Douglas-Fir Needle Midges have been found in Schuylkill and York County. These adults will be breeding for a week. Control now to prevent egg laying in needles. Douglas-fir bud break is drawing closer, and so does the emergence of these damaging midges. Adults typically emerge from under the trees during a range of 200-400 GDD. The emergence traps are simply constructed from a box (cardboard or wooden) or a bucket with a clear jar protruding from the side. Sticky cards can also be used to help scout for the flying midges.

Rhabdocline and Swiss Needlecast

All Douglas Firs need to be treated for needle cast, regardless of size. Swiss Needle Cast is very aggressive and hard to play catch up with. Starting at bud break, it is recommended to start applications of Chlorothalonil (with a sticker to prevent wash off) at 7-10 day intervals through early-mid-June. Most growers are treating with three to five applications for maximum control. Timing is the most important part of this application. Buds are elongating, and you want to get the treatments made prior to a wet period (we certainly need one of those wet periods for other reasons!). Thorough coverage is key, and this is where the grower's weed management plan becomes important as well. Clean fields and air flow are important. If you are a grower seeing infected trees this Spring, recall how many sprays you completed last season. Two to three applications may not be enough, and you are seeing the damage now. Consider adding more sprays at the end of May-June. Heavily infested trees will have reduced growth this season, and will take several seasons to recover fully, that is, when proper management is followed. For more information, see the Penn State Extension factsheet on Douglas Fir Needlecast.

Other pests to note activity:

Elongate Hemlock Scale Males have been observed flying in York County. Cryptomeria scales are present on Fraser Fir, but do not have crawlers yet. Most Fraser Firs in our area are just starting to swell. Pine Bark Adelgid and eggs have been found on pine seedlings. For more information, see Penn State Extension's factsheet on Insects on Real Christmas Trees.

Cones

This will be a heavy year for cones as trees were severely stressed last growing season.  If you wanted to try spray management techniques to control cones of Fraser Fir, now is your window, as buds have not broken and cones are present. 

Bud Watch

Buds are swelling and elongating in Berks and Schuylkill Counties. If you haven't been checking your different blocks of trees, its time to get out there and start managing your trees for the growing season!

The next scouting report will be available May 1, 2025.