Christmas Tree Scouting Report: August 13, 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)

Cryptomeria Scale

The second generation of cryptomeria scale crawlers has emerged. It is now time to treat. Second-crawler emergence roughly aligns with 1,750–2,130 GDD (base 50°F) accumulation. To scout, focus on the undersides of needles, particularly on lower and inner branches where infestations often start. Trees with mottled yellow needles are common indicators of scale activity.

To detect crawlers, use sticky tape by wrapping double-sided or sticky black electrical tape with the adhesive side facing outward around twigs or needles on infested trees. This will capture the tiny, flattened yellow crawler stage before they form their protective shields. Crawlers are most vulnerable at this stage, making it the optimal window for control measures. Yellow sticky cards may also be used to track male flights and help time applications.

Cryptomeria scale infestations can affect Fraser firs of all sizes, not just larger market-ready trees. Regardless of tree height, timely intervention is essential to reduce scale populations, prevent spread, and maintain overall crop quality and health. The following plan offers a comprehensive strategy for both immediate knockdown and long-term suppression, using a combination of insecticides, cultural controls, and scouting practices tailored to trees at different developmental stages.

For growers who missed the first-generation spray window and are facing heavy Cryptomeria scale infestations on Fraser firs, immediate and strategic action is essential to bring these trees to market quality. Begin with Dimethoate for rapid knockdown. Apply at 1 pint per 100 gallons of water, ensuring thorough coverage. Avoid spraying during heat stress (>85°F), and reapply in 10–14 days if crawler activity continues. This product offers quick suppression, but its broad-spectrum nature can flare secondary pests such as spider mites. To minimize this, scout regularly and consider rotating with softer products such as Safari or Movento later in the season.

Movento (spirotetramat) should be applied during active tree growth, typically in late August through early September. Use at 6–9 fl oz per acre with a non-ionic surfactant to ensure systemic uptake. This product offers longer-term suppression and is softer on beneficial insects. Apply only when trees are actively photosynthesizing to ensure movement within the plant.

Centaur (buprofezin), an insect growth regulator, should be reserved for crawler stages next June. Apply at 34.5 oz per acre with full coverage when crawlers are active. It is safe for natural enemies and excellent for resistance management. Reapplication may be needed based on pressure and scouting results. A follow-up spray in July may be considered depending on population levels.

Culturally, remove and burn heavily infested or non-sellable trees to reduce inoculum and open the canopy for better spray coverage and air circulation. This step also reduces overwintering populations of scale and other pests. Avoid chipping heavily infested trees unless they can be composted at high heat away from production areas.

Monitor mite populations closely if Dimethoate is used. If mite levels increase, consider introducing miticides like hexythiazox or bifenazate if thresholds are exceeded, or encourage predatory mite activity by minimizing disruptive sprays. Mites thrive in dusty, dry environments, so irrigating and maintaining vegetation between rows can help suppress outbreaks.

Proper fertilization supports scale recovery but must be timed carefully. Apply balanced fertilizer in early spring to promote healthy flushing. Avoid late-summer nitrogen applications, which can encourage tender growth susceptible to pests and winter injury. Excess nutrients may also increase scale susceptibility and reduce tree form if growth is uneven.

Bagworm

In Pennsylvania, treating for bagworms in August requires a shift in strategy because many caterpillars have already matured and sealed themselves inside their protective bags. At this stage, insecticides are typically no longer effective, but monitoring and physical removal can still reduce the impact of infestations and help guide future control efforts.

Bagworms are moth larvae that feed on both evergreen and deciduous trees, with a strong preference for arborvitae, spruce, juniper, and pine. The female remains inside her bag throughout her life. In late summer, she emits a pheromone to attract winged males. After mating, she lays several hundred eggs inside her own bag and dies. These eggs overwinter and hatch the following spring, usually around late May or early June.

In August, pheromone traps can be placed on infested trees to detect adult male activity. These traps help monitor the timing and intensity of mating flights and are useful for planning chemical control the following year. While pheromone traps do not significantly reduce populations, they are valuable for timing early sprays when larvae hatch.

If any bagworms are still actively feeding and have not pupated, selective products like Bacillus thuringiensis (Bt) or spinosad may offer some control, but this window closes quickly as larvae seal their bags. The most reliable control method in August is hand-picking and destroying the bags, especially for small- to medium-sized trees. Removing and burning bags helps eliminate eggs and reduces overwintering populations.

For long-term success, plan to scout next spring and apply insecticides during the early larval stage, before the bags are fully constructed. This timing is critical for effective chemical control and should be guided by trap data and local degree-day models.

Needle Cast 

Reports of needle cast have been observed in our scouting area, particularly on lower and inner branches. This leads to yellowing and early shedding of older needles, which reduces tree density and overall market quality. Symptoms often appear first in areas of the canopy with poor airflow or where moisture lingers, making the lower third of the tree especially vulnerable. Growers should inspect these trees closely. Yellowing needles with rows of tiny black fruiting bodies on the undersides are a sign of infection. These fruiting structures block the stomata and interfere with normal needle function. Because August is too late in the season for effective fungicide application, growers should flag affected trees for treatment next year. Use flagging tape or mapping tools to mark trees showing moderate to severe thinning or yellowing. This will help prioritize spring fungicide applications when treatments are most effective.

The ideal time to apply fungicides is between budbreak and early shoot elongation, typically from mid-May through mid-June in Pennsylvania. Treatments should focus on newly emerged needles before infection occurs. Chlorothalonil products such as Bravo Weather Stik are often used at rates of 1.5 to 2 pints per 100 gallons. Two to three applications spaced three to four weeks apart are recommended for effective coverage; this season, many growers applied four to five applications. Copper-based products may also be used as part of a rotation to manage resistance. Thorough spray coverage is essential, especially in the interior and lower parts of the tree where humidity is high and airflow is limited. Use properly calibrated equipment capable of reaching into the canopy. Spraying just before a rain event should be avoided to prevent wash-off.

In addition to chemical control, cultural practices can reduce disease severity. Shearing to open the canopy improves airflow and light penetration. Avoid crowding and manage ground vegetation to reduce humidity. Over-fertilization should be avoided, as excessive growth can promote conditions favorable for infection and result in uneven tree shape. August is a good time to scout for Swiss needle cast and flag trees showing symptoms for spring management. Plan for timely fungicide applications next season, and combine chemical and cultural approaches to protect tree health and maintain marketability.

We look forward to seeing and meeting new faces at the Pennsylvania Christmas Tree Growers Association Summer Meeting this week. Visit PA Christmas Tree Growers Association to get information. Kelly will be speaking about scouting and sharing more about our reports! The scouting team welcomes feedback for our first growing season back in action!  Please share any thoughts you may have so we can continue to serve you best! Email Kelly Piccioni at keg200@psu.edu.  

Scouting reports will be posted on as needed basis for the rest of the season.