2026 Christmas Tree Scouting Report April 9, 2026

Weather Update

This past week brought a classic early spring pattern across Pennsylvania with several warm days pushing temperatures into the 50s and low 60s followed by rapid drops into cold nighttime conditions. These fluctuations are slowing overall insect development while still allowing for brief windows of activity during warm afternoons. Soil temperatures are hovering around 50 degrees in many locations, which is an important biological trigger for early season pests.

Accumulated growing degree days continue to vary by region. Reports indicate approximately 143.5 GDD in the York area (zip 17019) as of April 6, while Schuylkill County is slightly behind at 116 GDD. These differences are reflected in pest activity and bud development across sites.

Tree development is progressing, with bud swelling and early elongation now visible, particularly on smaller and more exposed trees. This stage increases susceptibility to certain pests and is an important timing marker for scouting and management.

Insect Pest Update

White Pine Weevil

No widespread activity has been confirmed at this time. In York County, no weevils were captured in traps this week despite favorable temperatures. In Schuylkill County, activity was limited to a single warmer site where 17 adults were captured on April 1 and 4 adults on April 4, coinciding with soil temperatures between 60 and 62 degrees.

Across Berks County and surrounding areas, no feeding on leaders has been observed. Growers should continue monitoring terminal leaders closely, especially in historically infested blocks and warmer microclimates. Activity is expected to increase quickly with sustained warming.

Spruce Spider Mite and Eriophyid Mites

Spruce spider mite eggs are present across multiple regions, though hatch remains limited due to cold nighttime temperatures. No significant mite activity has been reported in York County, and Berks County reports indicate no confirmed hatch at this time.

In Schuylkill County, active eriophyid mites have been observed on Fraser fir and white spruce. Additionally, one spider mite crawler was identified along with eggs that are darkening and beginning to swell, indicating hatch is approaching. Activity is currently confined to warmer periods of the day.

Growers should focus scouting on interior foliage and lower branches where overwintering eggs are concentrated. As temperatures stabilize, expect a more synchronized hatch.

Balsam Twig Aphid 

No balsam twig aphid activity has been observed across reporting regions including York, Schuylkill, and Berks Counties. Bud development is approaching the stage where monitoring becomes increasingly important, particularly as buds continue to swell.

Spruce Adelgids 

Cooley spruce adelgid has been observed, including one report of a severe infestation on spruce at a farm in Schuylkill County. Eastern Spruce Gall Adelgid was also found on Norway Spruce in Schuylkill County. Growers should begin scouting for adelgids at the base of needles and along developing shoots. Early detection is important, especially in blocks with a history of pressure.

Cooley spruce adelgid and eastern spruce adelgid can look similar at first glance, but they differ in both identification and management, making accurate scouting important for proper control. The most reliable way to distinguish them in the field is by the type and location of galls. Cooley spruce adelgid produces very distinct cone like galls on new growth that resemble small green or purple pinecones at the tips of shoots. These are often preceded in early spring by small cottony masses at the base of needles. A key biological difference is that Cooley spruce adelgid primarily alternates between spruce and Douglas fir to complete its life cycle. Galls form on spruce, while the insect moves to Douglas fir for another stage of development where it remains exposed but does not form galls. In contrast, eastern spruce adelgid completes its entire life cycle on spruce alone, most commonly on Norway spruce and white spruce, and forms smaller galls at the base of new shoots rather than at the tips. It may also be observed as white cottony masses along needles and stems. Damage from eastern spruce adelgid is typically more subtle, showing as needle yellowing or thinning compared to the more obvious structural galling caused by Cooley. A simple scouting rule is that large cone like galls at shoot tips indicate Cooley spruce adelgid, while smaller galls at the base of shoots or cottony masses without tip galls are more indicative of eastern spruce adelgid.

Timing of management differs significantly between the two pests and is closely tied to growing degree days and bud development. For Cooley spruce adelgid on spruce, the critical control window occurs very early in the season, generally between 20 and 120 growing degree days, just prior to or at bud break. Applications must be made before gall formation begins, as adelgids become protected once galls are formed and sprays are no longer effective. During this window, target overwintering females and developing nymphs with horticultural oil or insecticidal soap, or use contact insecticides such as lambda-cyhalothrin or bifenthrin for stronger knockdown. Systemic products such as imidacloprid or dinotefuran can provide longer residual control, though fall applications are generally more effective for preventing gall formation the following spring. On Douglas fir, where Cooley spruce adelgid does not form galls and remains exposed, treatment timing is more flexible and typically aligns with periods of active populations later in the spring and summer, making both systemic and contact products effective.

For eastern spruce adelgid, management is generally more flexible because the insect remains more exposed throughout its life cycle. Early season applications of horticultural oil are highly effective against overwintering stages, typically within a similar early spring window around 30 to 120 growing degree days. Because galls form at the base of shoots and not at the tips, and because some populations remain exposed, additional applications can be made as needed when cottony masses and active populations are observed. Systemic insecticides such as imidacloprid or dinotefuran provide extended control, while contact materials including oils, soaps, or pyrethroids like lambda-cyhalothrin can be used for quick knockdown when populations increase.

In practice, this means spruce should be the primary focus for both pests, with very tight, early timing required for Cooley spruce adelgid before galls form, while eastern spruce adelgid allows for a broader treatment window. Douglas fir should be included in the spray program when Cooley spruce adelgid is present, as it serves as an alternate host and can sustain populations even if spruce alone is treated.

 For more information, read: Cooley spruce gall adelgid and Eastern spruce gall adelgid

Cryptomeria Scale 

Cryptomeria scale remains in the overwintering stage. Observations from York County confirm that scales are still under their protective covering with no eggs present at this time. Dissection shows the feeding structure inserted into the needle, but crawler emergence has not yet begun.

This is a key reminder that crawler timing is still ahead, and current management efforts should remain focused on monitoring rather than treatment.

Bud Development and Key Takeaways

Bud swell and early elongation are now clearly visible across regions, with smaller and more exposed trees advancing the fastest. This stage is critical as it aligns closely with upcoming pest activity including balsam twig aphid and adelgids. Warm daytime temperatures are beginning to drive early pest activity, but cold nights are slowing development and creating uneven emergence patterns. White pine weevil activity remains limited but has been confirmed in localized warm sites. Mite eggs are present and beginning to develop, with minimal hatch so far. No balsam twig aphid activity has been observed yet. Cooley spruce adelgid is present in some areas and should be actively scouted. Cryptomeria scale remains dormant with no egg development at this time.

This is a transition window. Stay ahead with scouting, especially in historically active blocks and warmer microclimates, as pest activity can increase quickly with the next stretch of consistent warm weather.

Next Report

The next scouting report will be available on April 16, 2026. Reminder, please submit observations anytime prior to Tuesday, April 14, 2026, by noon to Kelly Piccioni at keg200@psu.edu to be included in the next report. As a reminder, you may also call into the hotline weekly for updates: 1-800-PENN-IPM (1-800-736-6476) option 5.