The fungus grows upward into the water-conducting vessels of the plant and interrupts water movement. If plant roots and other tissues that die of Verticillium wilt are not removed from the soil, numbers of microsclerotia may greatly increase. Symptoms Trees, shrubs and woody ornamentals affected by Verticillium wilt may show both external and internal symptoms of the disease. Mild, chronic symptoms are general yellowing of the foliage, leaf scorch, reduction in twig growth, dieback of twigs and branches, sparseness in the crown or an abnormally heavy seed crop. Severe, acute symptoms are rapid defoliation, wilting and dying of leaves on individual branches, death of branches or rapid defoliation of the entire plant.
Symptoms often appear in only one branch, one side or one section of the plant.
A sudden wilt of the crown and death of the entire plant may occur, especially during hot, dry weather. Recurrence of symptoms the following year is unpredictable. Plants with mild, chronic symptoms one year may show more severe, acute symptoms the next year, may not have symptoms for several years or may recover completely. About half the plants showing wilt symptoms usually wilt in succeeding years. The extent of branch dieback in the current year is often not related to the previous year's symptoms.