Contributed byR. D. Martyn
Purdue UniversityBotany & Plant Path. Dept.West Lafayette, IN 47907-1155
Fusarium crown and foot rot of squash and pumpkin is caused by a forma specialis of Fusarium solani (Mar.) Sacc. The pathogen exhibits host specificity and exists as races, like the formae speciales of F. oxysporum causing vascular wilts of cucurbits. Fusarium crown and foot rot of squash was first described in detail in South Africa in 1932. It has also been reported in Australia, Canada, and the United States; however, its known distribution in the United States is limited. The disease has been described by various names, including wilt, root rot, foot rot, root and stem rot, and cortical rot.
Usually, the first symptom noticed in the field is wilting of the leaves. Within several days, the entire plant wilts and dies. If the soil is removed from around the base of the plant, a very distinct necrotic rot of the crown and the upper portion of the taproot is evident. The rot develops first as a light-colored, water-soaked area, which becomes progressively darker. It begins in the cortex of the root, causes cortex tissue to slough off, and eventually destroys all of the tissue except the fibrous vascular strands (Fig. 1). Infected plants break off easily about 2–4 cm below the soil line. The fungus is generally limited to the crown area of the plant. The main and lower portion of the taproot are not affected, except under extremely wet conditions. Likewise, the stem is not affected, except for the lower 2–4 cm immediately above the soil line. Plants showing symptoms develop numerous sporodochia and macroconidia, giving the mycelia a white to pink color on the stem near the ground surface. Fruits are attacked at the fruit-soil interface (Fig. 2); the severity of the fruit rot is dependent on soil moisture.
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