Christmas Tree Scouting Report: June 5, 2025

Weekly scouting report compiled by Kelly Piccioni, Penn State Extension, Schuylkill County. This week's scouting data contributors: Kelly Piccioni, Penn State Extension, Don deMackiewicz, Sarah Pickel and Cathy Thomas (PDA), Jim Fogarty (Schuylkill County), Rick Geissler (Berks County), Gerrit Strathmeyer II (Adams and York County) Paul Sheeler (Schuylkill County)

Pest Information

Needle Casts

Another wet weekend for us in Pennsylvania!  It has been nice to see the sun and dry out enough to get into the fields for growers to get their third or fourth application of chlorothalonil on their trees. When considering applying additional sprays than normal, take into consideration the density of a field (spacing), weed pressure, and tree size. If your fields are spaced close, with larger trees and tall weeds, the conditions for needle cast are favorable. If you are having problems with Swiss Needle Cast, note that it does sporulate later in the season than Rhabdocline Needle Cast. We have seen higher numbers of Swiss Needle Cast this season than in prior seasons, and therefore, additional sprays are recommended above the 2-3 applications of Chlorothalonil. Most growers are reporting four applications this season. While scouting, you should still be able to see the coverage of the chlorothalonil on the needles, showing they are protected. Soon, growth will begin to harden off, and it will not be as susceptible to infection as the fleshy, newer growth.

Diplodia Tip Blight

Diplodia tip blight affects stressed two and three-needle pines like Austrian, Scots, and red pine, and can also infect Douglas fir, causing browning and dieback of new shoots. On Douglas fir, look for wilted or brown shoot tips with resin-soaked needles, especially in the lower canopy. Tiny black fungal fruiting bodies (pycnidia) may be found at the base of dead needles or on cone scales. Scout in mid to late spring as new growth begins. Focus on browning shoot tips, especially in older or stressed trees. Use sanitary pruning techniques to remove infected shoots during dry weather, disinfect tools between cuts, and burn or destroy all infected material to prevent further spread. For chemical control, apply mancozeb. Chlorothalonil may not be consistently effective and is not the preferred option for high-pressure sites. Reducing tree stress and maintaining good air circulation also helps limit disease development.

Cryptomeria Scale

Cryptomeria scale eggs have been found, but no crawlers are active....yet. This warm end to the week will certainly help push them along. Cryptomeria scale is a persistent pest that targets Fraser, Canaan, and Korean fir and can be tough to spot without regular scouting. The scale insects settle on the undersides of older needles, especially on yellowed, mottled lower branches and in shaded areas. From a distance, affected trees may look dull, yellowed, or washed out. The scale appears as tiny, oval, light tan to yellow scales with a clear center. Begin scouting in areas where you’ve had issues before, as this pest often re-establishes in the same locations. Also, check the middle of the block, where spray coverage may not be as thorough. Peak crawler activity occurs through June and again in the second generation, late July through August. During these times, wrap black electrical tape sticky side out, around branches to catch crawlers—look for tiny, moving yellow specks. For chemical control, crawler stages are the best timing for treatment. Recommended products include dinotefuran, acetamiprid, or buprofezin. Paul Sheeler, Schuylkill County, recommends spraying systemics during the night to maximize the absorption of the product. When spraying during the day, it will dry quicker, and you may not get the desired efficacy. 

White Pine Aphids

White Pine Aphids on white pine have been observed in York County in small numbers. White pine aphid is a dark, soft-bodied insect with white waxy filaments that feeds on the undersides of needles, mainly on eastern white pine but also on spruce and fir. Infestations are most common in spring and fall, especially in shaded, crowded, or previously infested areas. Signs include yellowing needles, early needle drop, and sticky honeydew that can lead to black sooty mold. Scout regularly by checking the lower and inner branches. Encourage natural predators like lady beetles and avoid broad-spectrum sprays that harm beneficials. For control, use systemics like imidacloprid or dinotefuran. Apply during cooler parts of the day with good coverage, especially under needles. Healthy trees with good airflow are less likely to suffer serious damage.

Elongated Hemlock Scale

In York County, Elongated Hemlock scale and their crawlers are active on fir. Numbers are worse in sheltered areas in blocks with close spacing. Elongated hemlock scale is a persistent armored scale pest found on Fraser, Canaan, and Douglas fir, as well as true hemlocks. It feeds on the undersides of needles, causing yellowing, needle drop, and an overall thin, dull canopy. Scales appear as narrow, brownish covers aligned with the needle length. Scouting should focus on the undersides of older needles, especially in the lower and interior branches, where humidity is higher and sprays may not reach well. Look for yellow stippling on the tops of needles and the presence of scale covers or live crawlers. Peak crawler activity can occur throughout the growing season, but especially from late April through early summer, and again in late summer, depending on the region. Effective control requires multiple, well-timed treatments targeting the crawler stage. Recommended products include horticultural oil (1–2%), dinotefuran, buprofezin, or pyriproxyfen. Systemics are often more effective for high-pressure sites. Rotate products by mode of action and ensure good spray coverage, especially on needle undersides.

Bag Worms

Bag worms will soon be active and feeding. Bagworms are a serious pest on evergreens like spruce, fir, pine, arborvitae, and juniper. They create spindle-shaped bags made from silk and foliage, which hang from branches and blend in with cones. Larvae feed on needles, leading to thinning or complete defoliation in heavy infestations. Start scouting in mid to late June (around 600–900 GDD) for small, moving bags on branch tips, especially on sunny, exposed edges of fields. Old bags from last year can be removed by hand during winter to reduce eggs. For control, treat soon after hatch with Bt for young larvae or spinosad, diflubenzuron, bifenthrin, or lambda-cyhalothrin for larger ones. Thorough coverage is critical—bags protect older larvae.

Other Notes

Start to consider, if you have not already, a mowing program and herbicide program to keep your fields free and clear of weed pressure. 

The IPM Hotline is now accessible for Christmas Tree Scouting Information! Dial 1-800-PENN-IPM (736-6476), option  5  (Christmas Trees) to hear the latest update. 

We appreciate the feedback and look forward to more site visits!  Contact Kelly Piccioni at keg200@psu.edu to schedule a site visit to your farm. Visits are scheduled by area to maximize travel time and resources, but we are doing our best to meet the needs of our growers. If you have a programming idea, or other areas needing assistance, please reach out! Always rotate products by mode of action and confirm they’re labeled for use on Christmas trees in Pennsylvania.

The next scouting report will be available June 11, 2025