Christmas Tree Scouting Report: April 30, 2026

Frost/Freeze Damage

Frost injury remains present but limited and inconsistent across Douglas fir, Concolor Fir, and Norway Spruce.  Microclimates and variability of shoot elongation coincide with the percentage of damage observed. In York County, a sample of 120 branch tips across 12 trees showed approximately 20 percent damage on average, although individual trees varied widely, with some showing significantly less injury. In other locations, damage was typically observed on 10 to 20 percent or fewer of growing tips and was often confined to one side of seedlings or scattered individuals. Other fir and spruce species were minimally impacted as they have yet to break bud. In Schuylkill County, low temperatures of 21degrees on 4/20 into 4/21 were captured on a field thermometer. Hardwoods such as oak, honey locust, sycamore, redbud, Japanese Maple were the hardest hit by the temperatures. In the northern part of the state, most buds have not broken, or just started to break and minimal damage was observed.  Overall, on evergreens, frost injury is not considered severe or widespread, and most trees are expected to continue normal growth.

Pest Information

Most species are at or just beyond budbreak, with some locations moving into early shoot elongation. Damaging frost and freeze temperatures were observed across much of the state over the past week, impacting newly emerging growth on susceptible species. Injury has been most noticeable on Douglas fir, with additional damage observed on Concolor fir and Norway spruce, where tender new shoots were exposed during early elongation. Despite these events, overall development continues to progress, with significant variability between sites driven by microclimate differences. 

Douglas Fir Needle Midge 

Douglas fir needle midge has been detected in Schuylkill County, confirming that adult activity is underway in the region. Midge were captured in traps during this scouting period, treatments are being applied in alignment with host development, as most Douglas fir have moved beyond budbreak and into early elongation. Adult emergence and egg laying typically begin around 250 to 400 growing degree days, and current conditions are favorable for continued activity. Continued monitoring over the next one to two weeks will be important, particularly in areas where activity has already been confirmed. Early-season insecticide applications included with fungicide sprays may provide initial suppression during this window. Commonly used active ingredients for management include spinosad, abamectin, and pyrethroids such as bifenthrin, depending on timing and target stage.

Balsam Twig Aphid

Balsam twig aphid was treated last week, and no significant activity was observed during this scouting period. Activity generally coincides with budbreak, typically between 100 and 250 growing degree days. In Fraser fir, applications targeting balsam twig aphid and spruce spider mites are most effective when made prior to budbreak, and those timings should now be largely complete. Populations appear to be effectively managed at this time, and inclusion in early fungicide applications has contributed to control. Active ingredients commonly used include insecticidal soaps, horticultural oils, and products containing acetamiprid or flonicamid for aphid suppression.

Mites 

Heavy populations of spruce spider mites have been observed in some plantings, with significant numbers of eggs and active stages present. These populations appear to be a carryover from last season and are building quickly under current conditions. Spruce spider mites are cool-season pests that can reproduce rapidly in spring and fall, with generation times as short as one to two weeks, depending on temperature. Females lay multiple eggs over their lifespan, and populations can increase rapidly if left unchecked. The presence of both eggs and crawlers at this time indicates overlapping generations and active population development. Early-season control is critical to prevent population buildup before warmer temperatures reduce activity and shift pressure later in the season.

Growers are sharing success with miticides such as abamectin and spirodiclofen, marketed as products like Avid and Envidor, which provide effective control across multiple life stages. Envidor is particularly effective on eggs and immature stages, while Avid provides a strong knockdown of active mites. These products are most effective when applied early in population development and with thorough coverage. Given the high egg load observed, follow-up applications or rotation of modes of action may be necessary to achieve full control. Monitoring should continue closely over the next several weeks to assess population trends and treatment effectiveness.

Scale

Elongate hemlock scale was observed on some fir, with mottled needles present. Examination of scale revealed eggs beneath the coverings, indicating populations are actively developing. Crawler emergence is expected in May and typically occurs between 360 and 450 growing degree days. This stage is the most susceptible for control. Monitoring should continue closely for initial crawler activity, and systemic products may be used ahead of emergence to target developing populations. Active ingredients commonly used include dinotefuran, imidacloprid, and spirotetramat, with contact products such as horticultural oil or insect growth regulators used at crawler emergence.

Cryptomeria scale crawlers have not yet been observed. Crawler emergence generally overlaps with elongate hemlock scale, typically between 350 and 450 growing degree days. Monitoring for flagging heaving population areas should begin in the coming weeks as temperatures continue to warm. Similar management strategies apply, with systemic and contact options including dinotefuran, imidacloprid, and horticultural oil targeting crawler stages.

White Pine Weevil

White pine weevil activity has not been observed in traps during this scouting period. Most white pine in Southeastern Pennsylvania have already been treated in alignment with soil temperatures reaching approximately 50°F and expected adult emergence. Activity typically begins between 50 and 150 growing degree days, with peak activity shortly after. Current timing suggests that primary control measures have already been implemented for most sites, though continued monitoring is recommended. Common active ingredients used for control include bifenthrin, permethrin, and other labeled pyrethroids applied prior to egg laying.

Spruce needle rust

Spruce needle rust has not been observed during scouting, but it is likely present at low levels. Infection typically occurs during budbreak and early needle expansion under moist conditions, generally between 200 and 350 growing degree days. Current fungicide applications targeting Stigmina may provide incidental protection. Continued monitoring is recommended as buds continue to develop. Management of Stigmina and Rhizosphaera needle cast on spruce should be approached as a preventative program focused on protecting newly emerging needles each spring. Both diseases infect only the current season’s growth, so once symptoms appear on older needles, fungicide applications will not reverse that damage. The goal is to prevent infection during the window when new needles are expanding, typically beginning at budbreak and continuing through early shoot elongation. This generally aligns with the period when new growth reaches about one half to two inches in length, often between 200 and 350 growing degree days depending on site conditions.

Chlorothalonil products remain the standard and most reliable protectant for both diseases, with mancozeb also commonly used in rotation to improve coverage and resistance management. Copper products may provide some suppression but are generally less consistent under field conditions. Most growers should be planning for a two to three spray program, starting at early needle elongation, followed by a second application seven to ten days later, and a third application ten to fourteen days after that if wet weather persists or disease pressure is high. Thorough coverage is critical, particularly in the lower canopy and interior branches where these diseases tend to initiate.

Given the frequent moisture and moderate temperatures typical of spring in Pennsylvania, infection conditions are often ideal, especially in dense plantings with limited air movement. Growers should not rely on a single application, as extended periods of needle elongation and rainfall can reduce residual protection. A well-timed, multi-application program during this early growth window is the most effective way to maintain needle retention, color, and overall tree quality over time.

Needle Cast on Douglas Fir

Swiss needle cast and Rhabdocline needle cast are both present in Douglas fir, which are now largely past budbreak and into early shoot elongation. New growth has reached a stage where it is highly susceptible to infection, and protective fungicide applications are underway. Most growers have now made their first application for needle cast control, often using chlorothalonil products such as Bravo, and many have included an insecticide in that initial spray to also target early-season pests such as Douglas fir needle midge, adelgids, and aphids. This remains a critical timing window, as both Swiss and Rhabdocline infect only newly emerging needles. Infection risk begins around budbreak and continues through early needle elongation, generally between 200 and 300 growing degree days, particularly under wet conditions. As new growth continues to expand, maintaining fungicide coverage with follow up applications will be essential to protect current season needles and prevent further disease development.

Looking ahead

Looking ahead, growers should expect continued rapid development as growing degree days accumulate, with many pests and diseases transitioning into more active and susceptible stages. Douglas fir needle midge activity is expected to increase over the next one to two weeks, particularly in areas where adults have already been detected, and growers should continue monitoring traps and newly expanding shoots for signs of egg laying. Elongate hemlock scale and cryptomeria scale will be key pests to watch, as crawler emergence is expected soon, typically between 350 and 450 growing degree days, and this will be the most effective timing for control. Spruce spider mite populations should continue to be monitored closely, especially in blocks with known carryover populations, as eggs are hatching and multiple life stages are present, allowing populations to build quickly under favorable conditions.

On the disease side, the protection window for Swiss needle cast and Rhabdocline on Douglas fir remains open as long as new needles are expanding, and follow up fungicide applications will be important, particularly if wet weather persists. Spruce growers should be watching closely for budbreak and early elongation to properly time applications for Stigmina and Rhizosphaera, especially in blocks that are slower to develop. As conditions warm, growers should also begin watching for the shift from cool season mite activity to other mid season pests, while continuing to scout for any delayed frost effects or uneven growth recovery. Overall, the next two weeks will be critical for staying on top of both disease protection and early insect management, reinforcing the importance of frequent, block by block scouting and timely applications.

Next Report 

The next scouting report will be available on May 7, 2026. Reminder, please submit observations anytime prior to Tuesday, May 5, 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.