2026 Christmas Tree Scouting Report March 12, 2026

Welcome to the 2026 Christmas Tree Scouting Report

Welcome back to the Christmas tree scouting report. We would like to thank our weekly staple contributors and a special thank you to IPM specialist, Don deMackiewicz, for his time and commitment to this report. We would also like to thank our 2025 participating farms for allowing us to scout and report important data to growers. We look forward to working with growers and new contributors this year!

As we begin the 2026 scouting season, it is helpful to reflect on what we observed across Pennsylvania during the 2025 growing season and how those observations can guide our scouting priorities moving forward. Last year reinforced something that we see time and time again in Christmas tree production: weather patterns largely determine both pest pressure and how trees respond to that pressure.

Throughout the 2025 season, the Penn State Extension Christmas tree scouting reports tracked pest development across the state as temperatures accumulated and growing degree days increased. Early season observations focused on pests that emerge during bud development and early needle elongation. Douglas-fir needle midge activity began around bud break, when adult midges emerge and lay eggs on expanding needles. Because larvae quickly enter the developing needles, the opportunity for treatment is short and requires careful monitoring during this stage of tree development.

Balsam twig aphid activity was also observed during bud swell and early shoot expansion. Feeding by these aphids causes curled and distorted needles on fir species, particularly Fraser fir. While the damage is primarily cosmetic, it can significantly reduce the appearance and marketability of trees approaching harvest.

At the same time, spruce gall adelgid and Cooley spruce gall adelgid resumed feeding as temperatures warmed in spring. Feeding during this stage initiates gall formation on new growth, which later develops into the cone-like galls commonly seen on spruce.

As temperatures increased into late spring and early summer, white pine and spruce weevils became active and began feeding and laying eggs in terminal leaders. Damage from these insects typically becomes visible later in the season as dead or crooked leaders. Blocks with a history of weevil damage were monitored closely during this period.

Spider mites were one of the most consistently observed pests during the 2025 scouting season. Populations began building during warm periods in late spring and increased significantly as hot, dry conditions developed through the summer months. Drought stress appeared to increase tree susceptibility to mite feeding, and damage was commonly observed as needle stippling, bronzing, and premature needle drop. In many locations, mite pressure remained high for much of the growing season.

Later in the season, elongate hemlock scale and cryptomeria scale were observed in some plantings. Crawler stages were present during the typical summer generation periods and represent the most effective timing for control. Feeding by these armored scales can contribute to needle yellowing and reduced vigor when populations become established. The drought conditions experienced during 2025 likely intensified the visibility of both mite injury and scale damage, as stressed trees were less able to tolerate feeding pressure.

These observations highlight the importance of regular scouting throughout the season. Consistent monitoring allows growers to detect problems early, identify the correct cause of symptoms, and make informed management decisions. Effective scouting is not about reacting to problems after damage appears, but about observing changes in tree development, pest activity, and environmental conditions before they become larger issues.

The weekly scouting report is strongest when it reflects observations from across the state. Growers, extension educators, and industry partners are encouraged to contribute observations from their farms or regions. If you would like to share what you are seeing in your plantings, please send your notes, photos, or observations to Kelly Piccioni at keg200@psu.edu Information should be submitted by Tuesday at noon each week in order to be included in that week's scouting report.

Your observations help make these reports more useful for everyone across Pennsylvania’s Christmas tree industry. Thank you for contributing to another season of collaborative scouting.

Growing Degree Day Guide for Common Christmas tree Pests

100 GDD or less (late March to early April in many parts of Pennsylvania)
Begin scouting fields as trees come out of dormancy. Balsam twig aphid eggs overwinter on twigs and begin hatching as temperatures warm and buds begin to swell. Early feeding occurs on expanding shoots and can cause curled or distorted needles if populations are high.

7–58 GDD and continuing through spring (late March to May depending on location)
White pine weevil adults become active on warm days and begin feeding and laying eggs in terminal leaders of spruce and pine. Monitoring leaders during warm early spring days helps detect early activity before egg laying progresses.

30–100 GDD (late April to early May)
Balsam twig aphid activity increases during bud swell and early shoot expansion. Once needle distortion becomes visible it is often too late for effective control, so monitoring during early bud development is important.

22–170 GDD (mid April to early May)
Spruce gall adelgid resumes activity on spruce. Overwintering females lay eggs near expanding buds and nymphs begin feeding, initiating the pineapple-shaped galls that develop later in the season. Treatments must occur before gall formation begins.

General reminder for growers: Not all pests were included in this quick early season reference.

Growing degree days provide a useful guide for anticipating pest development, but scouting remains the most important management tool. Local weather conditions, site differences, and tree species can all influence pest timing. Combining GDD tracking with regular field observations allows growers to better anticipate pest activity and apply treatments when they are most effective.

Disease pressure, nutrient stress, and Douglas-fir needle burn in 2025

The 2025 growing season brought several weather patterns that influenced disease development, nutrient uptake, and overall tree health in Christmas tree plantings across Pennsylvania. Early spring conditions were generally cool and wet, creating favorable conditions for several foliar diseases. Extended periods of leaf wetness can promote needle cast infections and other fungal diseases that rely on moisture for infection. Early season scouting focused on monitoring for needle discoloration and needle drop that may have resulted from infections occurring during the previous growing season.

As the season progressed, weather patterns shifted to extended periods of heat and limited rainfall during the summer months. These drought conditions reduced soil moisture and limited the ability of trees to move nutrients through the root system and into the canopy. Because many nutrients move with water through the plant, drought can temporarily limit nutrient uptake even when soil fertility levels are adequate.

One of the most commonly observed symptoms during the 2025 season was yellowing in the upper canopy of fir species including Fraser, Canaan, and Nordmann fir, with similar symptoms also appearing in some spruce plantings. In many cases, this yellowing occurred on current-season growth during periods of prolonged dry weather. Foliar analysis from several sites indicated that magnesium, iron, and calcium uptake were lower than optimal in some samples. Magnesium plays a central role in chlorophyll production, while iron and calcium move into the plant primarily with soil water. When soil moisture is limited, uptake of these nutrients can be reduced, resulting in chlorosis or yellowing even when soil nutrient levels are adequate.

Douglas-fir plantings also showed visible stress symptoms during the 2025 season. Many growers observed needle scorch or “burn” on current-season Douglas-fir growth, particularly on exposed areas of trees during periods of intense heat and solar radiation. These symptoms were associated with a combination of environmental stress factors including drought conditions, a mid-season heat dome, and high light intensity. In some cases, residual chlorothalonil on needle surfaces likely contributed to the severity of injury under these extreme conditions. While chlorothalonil itself was not the direct cause, the combination of heat, sun exposure, and residue on the needles appeared to increase the likelihood of burn on sensitive new growth.

These observations reinforce the importance of pairing soil testing with foliar analysis when evaluating fertility and diagnosing nutrient issues in Christmas tree plantings. Soil testing helps determine the nutrients present in the soil, while foliar analysis provides a measure of what nutrients the tree is actually taking up and using. As noted by Dr. Rick Bates, foliar analysis is an accepted technique for diagnosing and monitoring mineral nutrition of Christmas trees because it measures nutrient concentrations directly in current-year needles and provides a strong indicator of overall site fertility and tree nutrient uptake.

Dr. Bates also emphasizes that foliar nutrient content is closely tied to the performance of the entire tree. When needle nutrition is adequate, overall tree health and growth are typically strong. Foliar analysis is therefore a useful tool for diagnosing nutrient deficiencies or imbalances, particularly when results are interpreted alongside soil test results from the same planting.

Growers who use foliar analysis typically sample twice during a rotation. The first sample is generally collected during the second or third year after planting, and the second sample is taken the year before harvest. Samples should be collected at the same time each year, with mid-September through mid-November considered the ideal window for collecting needle samples. Collecting samples consistently and pairing foliar results with soil tests provides a clearer picture of site fertility and helps guide long-term nutrient management decisions.

A foliar sample can be taken in early spring to help diagnose potential nutrient issues, especially when symptoms such as needle yellowing were observed the previous fall. Early season foliar sampling can sometimes help determine whether nutrient uptake may have been limited or if an imbalance contributed to the symptoms seen late in the season.

However, early spring foliar samples should be interpreted carefully because nutrient concentrations in developing needles are still changing as trees begin active growth. During this time, nutrients are actively moving into expanding shoots and needles, and concentrations may fluctuate depending on soil temperature, soil moisture, and overall tree stress. As a result, early season samples can sometimes reflect short-term environmental conditions rather than the long-term nutrient status of the site.

Even with these limitations, early sampling can still be helpful as a diagnostic tool when paired with a soil test from the same block. Comparing both results can help determine whether nutrients are present in the soil but may not have been effectively taken up by the tree due to conditions such as drought, saturated soils, or other environmental stresses.

If you experienced needle yellowing in the fall, collecting both soil and foliar samples this spring may help provide additional information and help rule out nutrient deficiencies or imbalances as a contributing factor. While early season results may be somewhat variable, they can still offer useful insight when working through the diagnostic process.

Visit the Penn State Agricultural Analytical Services Lab for testing information and forms.

Scouting Tool Recommendations

Don deMackiewicz shared valuable tools to gather as you begin to scout in your fields. These items will be beneficial to have on hand while working in your fields and scout for pests and diseases. If you find anything and need assistance with identification, having samples is very beneficial in addition to photographs. To track your own GDD, you can use links like green cast online or calculate your own:

The Growing Degree Day (GDD) for Christmas trees is calculated by averaging the daily maximum and minimum temperatures and subtracting the base temperature of 50°F, expressed as: GDD = [(Tmax + Tmin) / 2] - 50

In practice, if the calculated average daily temperature is equal to or lower than the base temperature, the GDD value for that day is recorded as zero. These daily totals are then added together over the course of the season to predict critical milestones such as bud break or the emergence of pests.

Scouting Reports Resume

We look forward to next week's report: Thursday, 3/19/26. Reminder, please submit observations by Tuesday 3/17/26 by noon to Kelly Piccioni at keg200@psu.edu. As a reminder, you may also call into the hotline weekly for updates: 1-800-PENN-IPM (1-800-736-6476) option 5.