Cyclaneusma minus (Butin) DiCosmo, Peredo, and Minter (syn. Naemacyclus minor Butin)
- Pines, esp. Scotch
- Also reported on Austrian, Ponderosa, Mugo, and Monterey pines
Symptoms and Signs
September Through November
- Light green spots that eventually become yellow on needles 2 years old and older
- Yellow needles with transverse brown bands
October Through May
- Symptomatic needles anywhere on the tree or cast to the ground
- Off-white fruiting bodies that develop on yellow needles and swell with wet weather, making them easier to see
Causes of Similar Symptoms
- Aphid feeding
- Other needle casts such as Lophodermium, Lophodermella, and Dothistroma
- Environmental stresses
- Air pollution
- Fall needle drop
- Winter injury
- Pine needle scale
Cyclaneusma needle cast is commonly referred to as the “fall yellower” of Scotch pines because of the timing and appearance of initial symptoms. Symptoms appear on older, interior needles from 10 to 15 months after infection occurs. In late summer or early fall, infected needles will have light green to yellow spots reminiscent of aphid or scale insect feeding. Gradually, these yellow spots enlarge to form yellow bands, eventually causing the entire needle to turn yellow. By winter, the needles are light tan, and brown transverse bands become visible. Infected needles remain on the tree through the winter. Fruiting bodies form about one month after symptoms appear. Because they are off-white in color and similar to the surrounding diseased tissue, they are difficult to detect. These structures become more obvious during periods of moist weather when they swell and split the epidermis of the needle, causing it to look like two open doors.
Because many needle casts are similar, laboratory diagnosis may be warranted for proper identification before applying a fungicide.
Biology and Life Cycle
Cyclaneusma needle cast causes many pine species to prematurely defoliate. Some research suggests that this fungus may be an opportunistic pathogen that causes disease on plants that are under environmental stress. Four periods of infection occur for this fungal disease. The first is from mid-July through August, when the current year’s needles may become infected. September through November and late November through early December are the second and third infection periods. In Pennsylvania, these three periods account for about half of the new infections. The remaining 50 percent of infections occur from April through June, when both mature needles and new growth are susceptible.
Spores are dispersed by the wind as they are released by fruiting bodies. If proper moisture is present, the fungus will enter the needle through stomata. About the time needles become discolored with brown bands, fruiting bodies will develop beneath the surface of the needle (Figure 1). They begin to swell and the epidermis of the needle opens with a longitudinal fissure (Figure 2). When moist or wet, the fruiting bodies
Figure 1. Yellow-brown bands on infected Scotch pine needles. Courtesy of Tracey Olson, PDA
Figure 2. Swollen, light brown fruiting bodies that will rupture the surface of the needle. Courtesy of Joseph O’Brien, USDA Forest Service, Bugwood.org (#5050047)
Disease Cycle Calendar (single year's growth of needles)
Throughout the year, spores are released from infected needles that are attached or have fallen from the tree (Figure 3) when the temperature is above freezing and there is moisture on the needle. Infected needles may remain on the tree or be cast anytime after they begin exhibiting symptoms (Figure 4.).
Figure 3. Cast needles may continue to sporulate. Courtesy of Joseph O’Brien, USDA Forest Service, Bugwood.org (#5050046)
Figure 4. Infected needles still attached to the tree. Courtesy of Joseph O’Brien, USDA Forest Service, Bugwood.org (#5050053)
Monitoring and Management Strategies
- Choose a site that will promote drying of trees (southern slope, good drainage, non-shaded).
- Provide adequate spacing between trees to allow for air circulation.
- Plant stock that shows resistance or tolerance to the disease; use seed stock that exhibits genetic resistance.
- Maintain proper nutrient and water levels to keep trees healthy and vigorous.
- Scout trees in susceptible areas for any symptoms of the disease (a hand lens may be required).
- Maintain proper weed control; do not allow weeds to grow up under or between the trees.
- Threshold level: If more than 20 percent of sampled trees have signs of the disease, consider treating the entire plantation.
- At the end of the season, evaluate results and update records.
- No recommendations are available at this time.
- Remove and destroy severely infected trees.
- Remove dead needles beneath infected trees.
- Examine needles around stumps for symptoms; remove infected needles if present.
- Shear non-diseased trees prior to diseased trees to minimize spread of the fungus.
- No recommendations are available at this time.
- Fungicide application: In Pennsylvania, five spray applications of an appropriate fungicide effectively treat the disease; spray in late March, early May, mid-June, mid-August, and early October.
- Buy disease-free and/or resistant stock from a reputable nursery.
- Scout in late fall for new trees just starting to show signs of infection.
- Avoid planting next to old Scotch pine stands that may harbor disease.