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Symptoms vary greatly between the different crops. Usually chlorosis appear on the older leaves first, later followed by necrosis. At some point, leaves develop a wilted aspect, often only on one side of the leaf, something called sectorial chlorosis or "one-sided wilt". This is intensified by warm sunny weather. On the stem a continuous black stripe appears and extends from the base upwards, but really entirely girdle it. When the vascular tissues are completely blocked by fungal growth, shoots also start to wilt and a brown discoloration of the vascular tissue can be observed. In trees, poor growth, early leaf senescence and staining of woody tissues may be the symptoms. Sometimes, at closer inspection with a lens, small black dots are visible in the dying tissue or on living tissue as well.
Verticillium wilt is caused by soil-borne fungi that can survive on crop debris in teh soil when non host is available. It enters the vascular tissue of the plant through the rootlets or wounds in the bark. Once inside the plant or the tree, it grows rapidly and blocks the transport of water and nutrients, resulting in the wilting and decay of the aerial parts. At later stages of the disease, the fungus colonizes the dying tissue and forms dark structures that can be observed with a magnifying lens. The fungus can survive several years at a location and is therefore a burden for .
Biofungicides containing Streptomyces lydicus break the life cycle of the fungus and can help to control the progression of the disease.
Always consider an integrated approach with preventive measures together with biological treatments if available. Application of soil fumigants is an effective, but expensive control tactic. The effectiveness depends on the chemical used, the rate, and the environmental conditions at the time of application.