. Bulletin. Natural history; Natural history. 450 Illinois Natural History Survhy Bulletin , Art. 6 with the three forms of the disease, vascu- lar, brown rot, and basal dry rot, have been published by AlcCulloch (1^H4), Massey (1926), Nelson (1948), and Mc- Clellan (1947). The symptoms common to all three forms of the disease are a brownish to black dry rot of the corm tis- sues; yellowing, browning, and death of the foiiage; and browning and destruction of the roots. The three forms of the disease have been distinguished mainly by effects on the corms. In the vascular form of the dis-
. Bulletin. Natural history; Natural history. 450 Illinois Natural History Survhy Bulletin , Art. 6 with the three forms of the disease, vascu- lar, brown rot, and basal dry rot, have been published by AlcCulloch (1^H4), Massey (1926), Nelson (1948), and Mc- Clellan (1947). The symptoms common to all three forms of the disease are a brownish to black dry rot of the corm tis- sues; yellowing, browning, and death of the foiiage; and browning and destruction of the roots. The three forms of the disease have been distinguished mainly by effects on the corms. In the vascular form of the dis- ease a sectioned corm will reveal a brown discoloration of the core and dark-colored vascular bundles extended laterally into the flesh, Hg. \B and C. In an advanced stage of the disease, the infected strands reach the surface of the corm at the nodes, and brown lesions develop at these points. In the brown rot form of the disease, tan, brown, or blackish lesions may occur anywhere on the corm but most commonly near the base, fig. 2. The rotted tissue is often quite thick and may extend all the way through the corm, fig. 2, bottom row. X^iscular discoloration is not associated with this form of the disease. The basal dry rot form of the disease differs from the brown rot form mainly in the thickness and position of the lesions. Basal dry rot lesions occur only on the bases of the corms and are usually re- stricted to the first and second internodes, fig. 3. The lesions are visible when the corms are dug and, under favorable curing conditions, they do not enlarge after har- vest. They rarely, if ever, extend deeper than 2 to -I- millimeters into the flesh. The diseased tissue is dark brown to black,. Fig. 2.—Picardy gladiolus corms affected with the brown rot form of the Fusarium disease. Above: bottom views of six corms with lesions of various sizes. Below: sections of three corms showing thickness of rotted Please note that these images are extracted from scanned p
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