Trichothecenes are produced by several genera of fungi including Fusarium, Stachybotrys, Myrothecium,Trichothecium, Trichoderma, Cephalosporium, Cylindrocarpon, Verticimonosporium, and Phomopsis. Trichothecene mycotoxins have also been isolated from Brazilian plants Baccharis.  however, all medically and economically important sources to date have been fungal, especially Fusarium. Fusarium is a major agricultural plant pathogen in temperate growing regions where it causes Fusarium head blight in wheat, barley triticale and other grains F graminearum has an optimum temperature range for growth of 26 28 deg  at a water activity (aW) 0.88 F culmorum grows optimally at 21 deg  when aW g 0.87. While increased rainfall will increase Fusarium head blight, the incidence of blight is primarily affected by moisture at anthesis flowering) when the temperature is in the optimum range.