The high heats of late spring/early summer can bring upon the onset of wilts. Verticillium wilt, a common occurring wilt, is caused by the fungus Verticillium dahliae Klebs. V. dahliae is widespread in soils throughout the county, with susceptible hosts in a large number of perennial and annual crops. Within perennial crops, almond and pistachio are susceptible hosts. Leaves turn light tan and die, and often remain on the tree. In some cases, particularly in pistachio, symptoms develop slowly over several years causing a thinning of the leaves and a corresponding loss in yield as the fungus progresses up the branch. Internally, the xylem wood turns dark, and a cross section will show a ring of discolored tissue. This darkened tissue will extend down the affected scaffold to the point of origin within the root system. Several scaffolds of the tree may be involved if the pathogen infected a large portion of roots. The fungus survives in the soil within survival structures known as microsclerotia. It enters the trees through the roots, infecting the xylem tissues of the plant. Upon infection, the fungus produces a dark pigmented substance that clogs the xylem tissues, preventing the upward flow of water to the scaffold branches. When the affected branches or leaves demand more water than it can receive due to the blockage, it collapses. Cool springs and wet soils favor disease development. The fungus is eliminated from the above-ground portions of the trees during the hot weather. The fungus may survive within the root and reinvade the upper part of the tree, but it is thought that repeated occurrences of wilt are caused by new infections each year. Within almond, young trees within their 2nd and 3rd leaf are the most susceptible to tree loss. All almond rootstocks and varieties are susceptible,