Red-Band (Dothistroma) Needle Blight

Red-band needle blight occurs throughout the growing season during wet periods. Initial symptoms include dark green bands on the needles, quickly replaced with brown or reddish-brown lesions.
Red-Band (Dothistroma) Needle Blight - Articles

Updated: November 21, 2017

Red-Band (Dothistroma) Needle Blight

Girdling lesions banding the needle. Courtesy of Tracey Olson, PDA

Mycosphaerella pini Rostr.

Anamorph: Dothistroma septospora (Doroguine) Morelet

Hosts

  • Austrian, Ponderosa, and Mugo pines highly susceptible
  • Scotch and red pines generally resistant

Damage Potential

  • Moderate

Symptoms and Signs

Late Summer Through Early Fall

  • Dark green bands on recently infected needles; bands may contain yellow or tan spots
  • Brown or reddish-brown bands and lesions on needles several weeks after infection

Late Fall Through Winter

  • Brown, dead needle tips with the base of the needle remaining green
  • Dark brown or black, tiny fruiting bodies in the dead portion of the needle

Late Winter Through Early Spring

  • Previously green base turns brown
  • Premature needle drop occurs (most severe on lower branches)

Causes of Similar Symptoms

  • Brown spot needle blight
  • Lophodermium and Cyclaneusma needle casts
  • Pine needle scale
  • Winter injury
  • Environmental stress

Identification

This disease, also referred to as Dothistroma needle blight, is called red-band needle blight because of the most common symptom found in the field. Although initial symptoms include dark green bands on the needles, these are quickly replaced with brown or reddish brown lesions. Only the base of the needle will be green, with the remaining portion tan or brown. Eventually, tiny, dark brown or black fruiting bodies are produced and release spores. The fruiting bodies are visible in the diseased area with a hand lens and are typically covered by a flap of needle epidermis.

Biology and Life Cycle

Red-band needle blight infection occurs throughout the growing season during wet periods. Beginning in May, spores are released from dark brown or black fruiting bodies that rupture through the epidermis of previously infected needles (Figure 1). The spores are spread by wind and splashing rain and enter healthy needles through the stomata. Second-year or older needles are susceptible to infection throughout the season. Current-year needles are not susceptible until they have elongated and hardened off, usually around July. Infection from cast needles on the ground below the tree is negligible.

Figure 1. Fruiting body rupturing the epidermis. Courtesy of Tracey Olson, PDA

After infection takes place, symptoms are not visible for 3–6 months on average. In late summer, infected needles may show dark green bands that look water soaked. This symptom occurs briefly and is usually not detected. Next, yellow to tan spots become visible and then eventually change to become larger, reddish-brown lesions banding the needle (Figure 2). The fungus produces a toxin that quickly kills the tissue at the infection site and causes it to turn purplish red, giving this disease its common name, red-band needle blight. Girdling lesions will result in needle tips dying while the bases of the needles remain green (Figure 3). By late fall, tiny, black fruiting bodies may appear in the bands or dead tissue. These will not mature and release spores until the following spring.Needle casting begins in fall and continues through late summer of the following year. The first to drop are the second-year and older needles that were infected in spring (Figure 4). Needles infected in the same year they are produced are usually not cast until late summer of the following year.

Figure 2. Reddish-brown lesions banding the needle. Courtesy of Tracey Olson, PDA

Figure 3. Dead needle tips resulting from girdling by lesions. Courtesy of Tracey Olson, PDA

Figure 4. Infected previous years’ needles will soon be cast. Courtesy of USDA Forest Service Archive, Bugwood.org (#2251050)

Disease Cycle Calendar (Single Year’s Growth of Needles)

Monitoring and Management Strategies

Plantation Establishment

  • Plant resistant or tolerant varieties such as Scotch or red pine.
  • Plant in an area with good drainage and airflow.
  • Plant trees with adequate spacing to allow for airflow.

Preseason

  • Control weeds in and around trees.
  • Remove and destroy lower whorls of branches to increase air circulation.
  • Scout for yellow needle spots, dead needle tips, and fruiting bodies in late fall or early spring; use a 15X hand lens to see the fruiting bodies.

Growing Season

  • If symptoms of disease are present, consider treating the plantation. Severely infected trees provide a good source for inoculum and should be removed.
  • Do not shear trees in wet weather. Shearing trees when foliage is wet may further spread the disease.
  • If disease is present in a block, shear disease-free stock first.
  • Maintain weed control practices.
  • At the end of the season, evaluate results and update records.

Control Options

Biological

  • No recommendations are available at this time.

Mechanical

  • No recommendations are available at this time.

Biorational

  • No recommendations are available at this time.

Chemical

  • Apply an appropriate protective fungicide once in mid-May to protect older foliage and again in mid-July to protect needles of all ages.

Next Crop/Prevention

  • Purchase and plant disease-free nursery stock from a reputable company.