Botryits Blight

Botrytis overwinters in the Northeast in moist, decaying plant tissue either as mycelium or as small, black, resting structures, or sclerotia. Damage includes shoot and branch injury.
Botryits Blight - Articles
Botryits Blight

New growth infected with Botrytis blight. Courtesy of Tracey Olson, PDA

Botrytis cinerea Pers.: Fr.

As the temperatures warm in spring, these resting structures start to germinate and threadlike mycelium will begin to cover the diseased tissue.

Hosts

  • All Christmas tree species

Damage Potential

  • Low

Symptoms and Signs

  • Spots on needles and shoots that appear water soaked
  • Blighted new growth that resembles frost damage
  • Brown lesions on needles and shoots that can grow and girdle the shoots
  • Gray, fuzzy, fungus structure on infected shoots and needles
  • When the fungus is dry, clouds of spores will be released when disturbed

Causes of Similar Symptoms

  • Atropellis canker
  • Diplodia (Sphaeropsis) tip blight
  • Cytospora canker
  • Frost damage
  • Pales weevil adult feeding

Identification

This fungal disease can infect hundreds of woody and herbaceous plants, including most species of trees grown as Christmas trees. This fungal disease does not produce typical fruiting structures as seen in other conifer diseases. Instead, Botrytis cinerea, or gray mold, produces a gray, weblike mycelium over the surface of the diseased area. Spores are borne on stalks on this hairlike growth.

Symptoms appear in spring and may follow frost damage or an extended period of shoot elongation due to cool temperatures. Infection will not occur on woody tissue, but the succulent new growth is susceptible. Infected tissue may appear water soaked and will eventually turn brown (Figure 1).

Figure 1. New shoot browned from Botrytis infection. Courtesy of Tracey Olson, PDA

Tip dieback may occur when the infected areas girdle the shoots (Figure 2). The disease develops under humid conditions with cool temperatures. Seedling beds are generally most susceptible to this blight because of the tight spacing.

Figure 2. Dieback of new growth caused by Botrytis. Courtesy of Rayanne D. Lehman, PDA

Biology and Life Cycle

Botrytis overwinters in the Northeast in moist, decaying plant tissue either as mycelium or as small, black, resting structures, or sclerotia. As the temperatures warm in spring, these resting structures start to germinate and threadlike mycelium will begin to cover the diseased tissue (Figure 3). Massive amounts of spores are formed on this mycelium, especially in the morning hours. They are spread to healthy tissue by wind or splashing water. When the spores come in contact with new plant tissue and during periods of high humidity or moisture, they will begin to germinate and penetrate the plant tissue. Spores can be produced continuously during moist conditions and may remain dormant for up to 3 weeks before they germinate.

Figure 3. Threadlike mycelium with spores covering infected tissue. Courtesy of Rayanne D. Lehman, PDA

This fungus can persist in either dead or living plant tissue. Infection typically takes place in shaded areas with high humidity, such as where trees are planted close together and on the lower branches of trees. A growing season that has an early warm spell, causing bud and shoot growth to begin, followed by an extended cool/ damp period, which suspends needle and shoot development, is especially favorable for Botrytis. This fungus is a relatively weak pathogen. New shoots that are injured by frost or mechanical means are most prone to this disease.

Monitoring and Management Strategies

Plantation Establishment

  • Space trees to encourage drying.
  • Control weeds to reduce the moisture level around the trees.

Preseason

  • Promote tree health by using good cultural practices, such as proper fertilization and adequate watering.

Growing Season

  • Scout trees that are densely planted and shaded. Look for tree shoots that appear rain soaked or exhibit the gray webbing.
  • Prevent tree injury from machinery.
  • Control damage from insects and other diseases.
  • At the end of the season, evaluate results and update records.

Control Options

Biological

  • No recommendations are available at this time.

Mechanical

  • Prune infected tips out of established trees after foliage has died. Disinfect shears with 70 percent alcohol or
  • Remove infected seedlings from seedling beds to prevent disease spread.

Biorational

  • No recommendations are available at this time.

Chemical

  • In general, fungicide sprays are unnecessary for established Christmas tree plantings.
  • For seedling beds, preventative fungicide sprays may be helpful in preventing infection during a cool, moist growing season.

Next Crop/Prevention

  • Do not purchase or accept infected nursery stock.