Christmas Tree Scouting Report: May 1, 2025

Weekly report 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

What a difference a week can make! We have bud break and needle elongation on Douglas Fir in every scouting location in Southeastern Pennsylvania. Chlorothalonil should be applied to protect the emerging needles from needle cast. For more information, see last week's report. Mites have been very active. Look for webs and a bleached/mottled look on needles. Applications should be made at this time. Review Extension's factsheet on eriophyid rust and sheath mites.  Growers in our scouting areas have treated for White Pine Weevil, and no live weevils have been found this week. No adults have been observed feeding after treatment this week. Soil temperatures have been in the mid to high 50-degree range in our scouting areas.  Don deMackiewicz shared a helpful reminder: Poison Hemlock is growing in our areas, and is often mistaken for Queen Anne's Lace and Wild Carrot. Purple splotches on stems help identify Poison Hemlock. Mowing it can cause respiratory issues. For more information to keep yourself and your crew safe from exposure, see Penn State's fact sheet on Poison Hemlock.

Douglas Fir Needle Midge 

Growers in Schuylkill and York Counties have sprayed applications to treat needle midge. No living midges have been found in the traps this week after effective treatment. The first insecticide spray should have been applied just before or at the first sign of bud break.  If midges continue to be seen in the block, a second insecticide application can be made two weeks after the first.

Balsam Twig Aphid 

Treatment for Balsam Twig Aphid should occur at this time, prior to Fraser and Canaan Fir bud break. See blow under "Bud Break Watch" for images of what buds look like currently on trees in Berks and Schuylkill Counties. Although we have not had activity in our scouting areas, growers are still treating for it to provide coverage for those trees. 

Elongate Hemlock Scale

Bright yellow, oval crawlers of elongate hemlock scale were starting to be seen this week on Canaan and Fraser Fir and Douglas-fir in York and Schuylkill Counties, this week and last. This armored scale can be found on the undersides of the needles, starting at the bottom and inside of the tree. Damage will be seen as yellow speckling on the top of the needles. The crawler emergence was still very light. Growers may see a heavier emergence over the next week and should consider starting insecticide treatments at that time. Hosts of this armored scale include true firs, hemlocks, spruce, Douglas-fir, and pines. Female scales are brown and oblong.  Male scales are smaller and covered with a white waxy coating.  Bright yellow, oval-shaped crawlers, or nymphs that hatch from eggs laid by the female, are the vulnerable stage of this pest. When crawlers are found moving on the foliage on the bottom portion of the tree, growers may want to consider applying an insecticide. 

Thrips

In addition to mites, Thrips have been found on around 50% of Fraser Fir in a block of trees in York County. Sarah Pickel and Cathy Thomas would like to note that thrips, in addition to the mites, can cause damage to new growth, and this stress will stimulate increased cone production. Imidacloprid is recommended for treatment on thrips. Yellow sticky traps can be clipped onto the branches with a clothespin to scout. 

Needle Cast

Rhabdocline and Swiss Needle Cast treatment should occur at around 10% bud break. Chlorothalonil remains a reliable active ingredient, with mancozeb or copper products as alternatives to treat needle cast. Growers treat with three to five applications throughout the growing season. Insecticides can be included with fungicides to treat Needle Midge and later applications to treat Cooley Spruce Gall Adelgid. If you have a more severe case of Swiss Needle Cast, it is recommended that the fourth and fifth applications be included.

Rhizosphaera and Stigmina Needle Cast (SNEED), symptoms begin on lower branches of spruce, where needles from the previous year develop purple to brown discoloration, eventually dropping prematurely. The most diagnostic feature—visible under magnification—is the presence of small black fruiting bodies (pycnidia) that emerge from needle stomata. While Rhizosphaera produces round and uniform fruiting bodies, Stigmina are irregular and often more abundant. Fungal spores spread during wet spring conditions, making May through early June the critical window for preventive management. Once new growth has fully expanded, it becomes increasingly difficult for fungicides to reach infection sites. Treatment recommendations include: First fungicide spray at 0.5–2 inches of new growth, followed by a second application 3–4 weeks later, depending on rainfall and disease pressure. While SNEED and Rhizosphaera may seem interchangeable in the field, both can lead to significant needle loss, reducing the salability of trees.

Key management practices facilitate the success of treating needle cast. Improving airflow between trees, avoiding overhead irrigation, and sanitizing pruning equipment can reduce inoculum and stress on susceptible trees. Monitoring high-risk areas, maintaining good cultural practices (such as weed management and proper air flow), and treating early and proper timing remain your best defenses against these needle cast diseases.

Bud Break Watch 

95-100% of Douglas Fir in York, Berks, and Schuylkill Counties have broken bud and began elongating. 

Less than 5% of Fraser Fir have broken bud in Berks, Schuylkill and York Counties, but expecting warmer days and nights to push the growth over the next week. 

70-90% of Norway Spruce have broken bud in our scouting area. Note Norway Spruce will break bud and elongate at a variation of times even within the same row. It is important to scout and evaluate when it is the best time to spray. Serbian and Blue Spruce have closer to a 5% bud break at this time in our scouting areas.  Small Hemlock have also started to break bud in our scouting areas of York, Schuylkill and Berks Counties.

Need help with your sprayer calibrations? Extension can help!

Winter Damage

Extension has received many calls, and has been on many site visits to observe and take samples of plant material that has suddenly displayed red blotchy needles, to fully red/dead plants. Almost every sampling of lab results indicated drought stress and winter desiccation. Fungal infections have appeared as a secondary infection.  When plants were removed entirely from the ground, "J" roots have been observed. Many of these factors combined contribute to the death of the plant. Penn State Extension has a fact sheet on. Winter injury observed in ornamental plantings

 If you would like to send samples on your own to the lab, visit the Penn State Plant Disease Clinic website for information on how to submit samples.

Other: 

Both the Eastern spruce gall adelgid on Norway spruce and the Cooley spruce gall adelgids on Blue spruce and Douglas-fir are becoming more noticeable because of the tufts of white waxy fringe that they develop at this time of the year. Unfortunately, the wax that helps them become more obvious also makes them invulnerable to insecticide sprays.  The time to treat these pests is in the fall after the black overwintering nymphs have settled, or in the early spring before they develop the wax. 

We are doing our best to get out and see every farm that has called, but please email pictures to Kelly Piccioni-  keg200@psu.edu  In some cases, we've been able to facilitate much quicker with those images. 

The next scouting report will be available on May 8, 2025