| 1402008 |
anthracnose |
Colletotrichum nicotianae |
This fungal disease is encountered in tobacco seed beds and occasionally in the field. Small gray-white, usually circular, spots develop on leaves. As lesions age and dry, they become papery and thin and are surrounded by a raised water-soaked border. Leaf tissues, especially veins and midribs, may appear "pitted" or sunken when viewed from the underside. The lesions become brown. Larger spots may have a dark brown center. Lateral veins on the lower leaf surface may turn dark. Affected leaves may become wrinkled and/or distorted. As the disease continues, the entire leaf may die. Small plants may be killed, resulting in large barren spots in plant beds. In the field, leaf lesions may be followed by cankers on midribs and stems. Anthracnose is favored by wet conditions and is sometimes confused with weather fleck. Symptoms of anthracnose are also similar to those of target spot. Target spot has more consistently circular, pin-head sized lesions which usually do not affect the major leaf veins until the whole leaf begins to die, whereas anthracnose often attacks leaf veins and petioles early in the disease development. |
| 1440009 |
anthracnose |
Colletotrichum nicotianae |
Symptoms of anthracnose include spotting of the leaves, development of cankers on midribs and veins of leaves, and eventual stunting and/or death of transplants. Leaf spots are at first pinpoint size, water-soaked, and depressed. They enlarge to approximately 3 mm in diameter, are light tan in the center, and have raised dark borders. Veins and midribs are often infected, causing the leaf to become distorted. On plants ready to transplant, large red-brown cankers can develop on the stems and petioles. Severely affected plants are killed. With the aid of a hand lens, fruiting bodies called acervuli can be seen in affected areas. These fruiting bodies produce pink spore masses and may have black bristle-like appendages called setae. The disease is most common in plant beds that are weedy and/or deficient in nitrogen. |
