2026 Christmas Tree Scouting Report June 25, 2026

Pests

Cryptomeria Scale

Cryptomeria scale development continues to progress across Pennsylvania Christmas tree plantings. Earlier reports documented crawler emergence beginning in early June, and most locations have now moved beyond peak crawler activity with adults settling in closing the window for effective treatment.

At approximately 1,046 GDD, crawlers were observed outside female covers with very few remaining eggs beneath scales. By 1,139 GDD, nearly all first-generation crawlers had settled and begun feeding. No active eggs or crawler emergence were observed beneath scales during scouting, indicating first-generation hatch is largely complete at these locations.

Beneficial insect activity was also observed within scale populations. Tiny parasitic wasps were found actively ovipositing into scales. These natural enemies can contribute significantly to population suppression when broad-spectrum insecticide use is minimized.

Unlike the staggered generations of EHS, Cryptomeria scale has two distinct generations during a growing season. The second generation typically occurs in early-mid August during a GDD range of 1,750-2,130. During each generation, the crawler emergence, which can be expected two weeks after eggs are first laid, may be staggered over a period of approximately 2-3 weeks. If growers make an insecticide application during the first week of crawler emergence, they will want scout for crawler activity a week later to see if a second application may be necessary.

Products labeled for scale crawler management in Christmas tree production should be timed to coincide with active crawler emergence for maximum effectiveness.

Bagworms

Bagworm development continues across Pennsylvania. At approximately 1,046 GDD, all bagworms examined had emerged from their overwintering bags, and no additional eggs were observed within the bags. This indicates hatch is essentially complete at this location.

Young larvae are actively feeding and constructing protective bags from host foliage. Early instar bagworms remain the most susceptible stage for management. As larvae continue to grow and incorporate larger pieces of plant material into their bags, insecticide efficacy may decline.

Growers should continue scouting arborvitae, spruce, fir, juniper, and other susceptible hosts. Carefully examine foliage for small, mobile bags that may blend into surrounding plant material. Management is generally most effective when directed toward young larvae before significant bag construction occurs.

This pest has one generation per year. The larvae, or bagworms, will feed on needles through-out the summer. As they increase in size, they continue to build up their protective cases from needle pieces. Newly emerged larvae will only partially eat needles, causing brown, ragged areas of the needles. As the bagworms grow, however, they will consume whole needles and are capable of stripping whole twigs. To prevent feeding damage from this pest, an insecticide can be applied when larvae are still small, but when the majority have exited the cases. In smaller populations, bagworms may be picked by hand later in the season if control is not achieved at this time. Recommended active ingredients include Bacillus thuringiensis var. kurstaki (Btk), chlorantraniliprole, spinosad, and diflubenzuron. These materials provide the greatest efficacy when directed at small, actively feeding larvae before bags become large and difficult to penetrate. Thorough coverage remains critical for successful control.

Fern Rust 

Some of the questions we've been receiving are about the appearance of tiny white tubular structures on the undersides of Concolor or other true fir needles. These are fungal fruiting structures (aecia) and are the signs of infection by a species of Uredinopsis rust – either fir-fern rust or fir-blueberry rust. The spore producing structures are lined up along the stomates of last seasons' needles and are only visible for a short window during the season. This is the time when spores are being released and will infect the alternate hosts.

There are over 20 species of rusts that attack true firs (Abies spp.) and alternate to woody plants like willow (Salix spp.) and blueberry (Vaccinium spp.) and herbaceous plants like mouse-ear chickweed and various ferns. Although these alternate hosts are quite common in PA, often growing in windrows or as weeds in plantations, the disease on true firs is somewhat rare, seldom causing significant damage, and likely goes undetected. Symptoms of true fir rusts include witches'-broom (Broom rust) and needle discoloration and defoliation.

 This season's newly emerged true fir needles would have become infected in early spring from spores liberated from diseased ferns. The spores from the fir are only capable of re-infecting the ferns and will do so when the fruiting structures (aecia) mature and sporulation begins. Later in the summer, the infected needles will cast and lead to a sparse appearing tree. Christmas tree growers of true firs can scout now for this disease, and if found, consider eliminating from their fields possible sources of these fungi – ferns, blueberries, willows.

Spraying fungicides on fir trees now for this disease will have no impact. In most Pennsylvania Christmas tree plantations, this disease is more of an occasional curiosity than a significant production issue. There are no fungicides currently recommended specifically for treating active fir-fern rust or fir-blueberry rust infections once symptoms are visible. Management is primarily achieved through sanitation, alternate host reduction, and monitoring of affected blocks. Trees may appear somewhat thin after infected needles are shed later in the season, but severe economic losses are uncommon.
- Reference: Selections from writings of Sarah Pickel and Tracey Olson, PDA plant pathologist

Fletcher Scale

Fletcher scale development continues on arborvitae and other hosts.The growing degree day range for this crawler emergence is 1029-1388 GDD.  At approximately 1,046 GDD, crawlers were still present beneath female scales, although most had already emerged. No eggs were observed beneath scales during scouting. Most crawlers had moved out from beneath the protective female covering and were actively settling on host tissue.

Growers should continue monitoring infested trees and shrubs for crawler activity. Double-sided tape remains an effective tool for detecting active crawler movement and evaluating treatment timing. Crawlers remain the most susceptible stage for management because they lack the protective wax covering present on older life stages. Recommendations include: pyriproxyfen, and other labeled crawler-targeted insecticides can provide effective suppression when applications are timed to coincide with active crawler emergence. Systemic insecticides such as dinotefuran and imidacloprid may also provide suppression where labeled.

This pest secretes honey dew, which can cause a build-up of unsightly, black sooty mold on the foliage. If the scale is a problem, growers can make an insecticide application when they begin to see the tan-colored crawlers moving on the foliage.

Beneficial Insects

Beneficial insect activity continues to increase throughout Christmas tree plantings. During scouting this week, parasitic wasps were observed actively attacking Cryptomeria scale populations. These natural enemies play an important role in long-term suppression of scale insects and other pests.

Growers are encouraged to note beneficial activity while scouting and consider potential impacts of broad-spectrum insecticide applications on natural enemy populations.

Fraser, Canaan, White Pine Needle Browning and Shoot Injury

Several isolated eastern white pine were observed with localized browning of current-season needles and shoot tips. Damage was generally confined to a small number of trees within otherwise healthy blocks and was most common on exposed trees located along roadsides, field edges, corners, and openings. Trees growing within denser plantings appeared largely unaffected.

Affected shoots remained green and viable beneath the bark, and needles were firmly attached despite discoloration. No evidence of Pales weevil feeding, Atropellis canker, Diplodia shoot blight, or significant needle cast disease was observed during scouting. The pattern of injury appeared scattered rather than block-wide.

Current observations suggest environmental injury may be responsible. Spring temperature fluctuations, frost events following periods of warm weather, and subsequent heat and wind exposure may have contributed to injury of expanding needles. The distribution pattern and lack of evidence for insect or pathogen activity support an abiotic cause at this time.

Growers observing similar symptoms should continue monitoring affected trees throughout the summer. Watch for progression of symptoms, canker development, resin production, or expansion into older foliage. Flagging affected trees now may help determine whether symptoms stabilize or progress later in the season.

Norway Spruce Samples submitted to the Penn State Plant Disease Clinic were evaluated for potential biotic causes. No pathogens were recovered from the affected spruce samples, and no needle cast or shoot dieback fungi were detected. Root tissue tested negative for Phytophthora using Agdia's ImmunoStrip assay, further supporting a non-infectious cause of the observed symptoms.

Current evidence suggests that the injury is most likely associated with environmental stress. Some branches exhibited browning and death of newly emerged growth consistent with frost or freeze injury that may have occurred during spring bud break and shoot elongation. Tender new growth is particularly susceptible to late-season freezes, and symptoms often become apparent several weeks after the initial injury event.

In addition to spring frost events, many areas of Pennsylvania experienced periods of unusually warm temperatures shortly thereafter. Trees with freeze-damaged cambial tissue may have been further stressed by subsequent heat and sun exposure. In exposed locations, this combination of frost injury followed by intense sunlight and elevated temperatures can result in additional tissue collapse, desiccation, and symptoms similar to sunscald. Damage was frequently observed on exposed trees, along roadsides, field edges, openings, and other locations where trees received greater sun and wind exposure.

Fraser Fir Cone Production

Several growers reported unusually light cone production on Fraser fir this season. Cone development in Fraser fir begins well before cones become visible, with reproductive buds initiated during the previous growing season. The number of cone buds that ultimately develop is influenced by a combination of environmental conditions, tree vigor, stored carbohydrate reserves, genetics, and cultural practices. Temperature and moisture conditions during the summer when reproductive buds are forming can influence the size of the following year's cone crop.

Fraser fir is also known to exhibit periodic cone production cycles commonly referred to as mast years. During mast years, large numbers of trees across a region produce abundant cone crops simultaneously, often followed by one or more years of reduced cone production. While the exact timing varies among locations and individual trees, many growers observe heavier cone crops every three to five years, with lighter cone production occurring in intervening years.

Researchers believe these fluctuations are partially related to the substantial energy investment required for cone production. Developing cones require significant amounts of stored carbohydrates and nutrients, which can temporarily reduce resources available for future reproductive development. Following a heavy cone year, trees may require several growing seasons to rebuild reserves before another large reproductive effort occurs.

The light cone crop observed by many growers this year may represent the lower phase of a natural mast cycle, environmental conditions that were less favorable for reproductive bud initiation during 2025, or a combination of both factors. Because masting often occurs across broad geographic regions, continued observations from multiple farms may help determine whether reduced cone production is occurring throughout Pennsylvania and other Fraser fir growing regions.

Next Report and Looking Ahead

There will be one more seasonal report will be provided until the second emergence of Cryptomeria scale in August. 

As always, growers should carefully read and follow the most current product label before making any pesticide application. Labels can change; rates may vary by crop or application method, and specific restrictions regarding PPE, reentry intervals, pollinator protection, and seasonal maximums must be followed. The Pennsylvania Department of Agriculture reminds applicators that "the label is the law" and that all pesticide applications must remain in compliance with both federal and state regulations.

The next scouting report will be available on July 1, 2026. Reminder, please submit observations anytime prior to Tuesday, June 30 , 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