Gray's Lily Disease

Botrytis

• Botrytis (Botrytis cinerea and Botrytis elliptica) is a fungal disease that can infect a wide range of plants, Gray's lilies included. The disease is characterized by oval-shaped or circular orange or reddish-brown spots on older leaves. In damp conditions, woolly gray fungus may appear on the spots. When in bloom, the fungus produces brown spotting. Botrytis cinerea invades dead or dying tissue such as a fallen petal or leaf. From there, it can begin to attack the healthy tissue that has been injured or has a dead area. Botrytis elliptica invades healthy tissue only. Because botrytis grows best in moist conditions, the University of California Integrated Pest Management recommends keeping humidity below 85 percent and avoiding overhead watering. Botrytis grows best in a temperature range of 70 to 77 degrees Fahrenheit. If possible, allow plant to dry between waterings to reduce the amount of moisture. Remove dead or decaying vegetation and old flowers where Botrytis can grow.

Anthracnose

• The leaves of a lily with anthracnose (Colletotrium sp.) develop tan to reddish-brown spots, usually close to the veins. The leaves may become cupped and distorted. Severely infected plants may lose their leaves. The disease spreads through water splash resulting from rainfall or irrigation. Although anthracnose can enter through wounds, it doesn’t need wounds to infect the plant. Dead leaves should be removed. Weeding and proper water drainage are also important. Fungal diseases are difficult to treat and fungicides are not always effective. Destroying the diseased plant and starting over may be the best option in getting rid of anthracnose.

Alternaria Leafspot

• The University of California Integrated Pest Management reports that Alternaria leafspot is caused by two species of fungus: Alternaria brassicae and Alternaria brassicicola. However, symptoms for each vary slightly. A. brassicae causes dark spots to appear that later become tan and circular. The spots of A. brassicicola are typically darker and can produce dark green spores on the spots, creating a concentric effect. Spots eventually become papery. Unlike anthracnose which spreads only through water spray, Alternia can also be spread by the wind. Infected leaves should be removed as well as entire plants that are severely infected.

Other Diseases

• Other diseases that have the potential to cause problems for Gray’s lily are bacterial soft rot, viral diseases (Lily symptomless virus, cucumber mosaic virus and Tulip breaking virus), and other fungal rot diseases such as bulb rot, basal rot, and root rot.