Tree Diseases: Lophodermium Needle Cast
Lophodermium needle cast is a fungal disease that affects two and three needled pines, as well as some five needled pines. The disease is caused by the fungus, Lophodermium seditiosum. In spring, needles infected the previous year will develop small, brown spots, with yellow margins. By summer, the infected needles turn yellow, and then reddish-brown. Fruiting bodies form on the needles once they have expired. Infected needles are often shed from the tree. Significant defoliation can disfigure infected trees, and reduce tree vigor. Severe infections may culminate in tree mortality.
Distribution & Range
Lophodermium needle cast is widespread throughout North America, and Europe. The disease occurs wherever susceptible pines are present.
Lophodermium needle cast commonly infects Scots and red pines. Ponderosa, Monterey, Virginia, and Austrian pines have also been reported as hosts, albeit with less frequency.
Needle infection begins in mid to late summer. Only the current year’s growth is vulnerable to infection. In summer and fall, fruiting bodies that have developed on infected needles rupture, and release spores. These spores are disseminated by air currents or splashes of rain to susceptible trees, where they initiate new infections. The fungus infiltrates the stomata of vulnerable needles, and becomes established within the healthy tissue. As the fungus expands within the infected needles, it kills the vascular cambium, preventing the transportation of water and nutrients. As the infection progresses, the needles die back, and are often shed from the tree. The fruiting bodies overwinter on the infected needles. They become active the following spring, and continue to develop. They reach maturity in summer, and begin to release spores, beginning the cycle anew.
Symptoms of Infection
In early spring, brown spots, or bands with yellow margins, appear on the previous year’s needles. As the spots or bands enlarge, the entire needle turns yellow, and then reddish-brown as the shoots become elongated. Severe infections will cause the crown of infected trees to appear scorched, with only tufts of green current-season needles remaining at the tips of branches. As the disease advances, infected needles generally drop from the tree. Defoliation often begins on the lower portion of the crown, before progressing upwards. In late summer, slightly raised, small, black fruiting bodies appear on the dead needles. The fruiting bodies are aligned length-wise on the needles. They feature a characteristic slit in their center, which splits open to release minute spores when conditions are sufficiently moist. These fruiting bodies may also be observed on cast needles under the tree. The current season’s growth will generally not exhibit symptoms of infection.
- When planting, select trees that are genetically resistant to the disease. Avoid planting susceptible trees in low areas with poor soil drainage. Adequately space trees to encourage the drying of foliage, and limit sporulation.
- Remove weeds growing around and under trees to improve air circulation, and the drying of foliage.
- In early spring, inspect needles for symptoms of infection. Severely infected limbs, and needle litter should be removed, and destroyed to prevent sporulation.
- Maintain tree vigor through sound cultural practices. Ensure that trees are sufficiently watered, especially during extended periods of drought. Apply a layer of organic mulch around the base to improve soil quality, moderate soil temperature, and maintain soil moisture.
- Registered fungicides can be applied three to four times during the growing season. Initial applications should be performed in early July, when the current year’s needles have fully expanded. Subsequent applications should be administered at three week intervals.
Photo courtesy of Ralph S. Byther