Reducing relative humidity through improved ventilation has proven a useful means of control. Among the compounds registered for use in Connecticut is thiophanate-methyl. Consult the label for dosage rates and safety precautions. Leaf spot, Cercospora calendulae , Alternaria , or Colletotrichum spp. Small spots appear which coalesce and progressively destroy leaves, stem, and eventually the entire plant.
Most varieties are susceptible.
Among the compounds registered for use in Connecticut is thiophanate-methyl. Consult the label for dosage rates and safety precautions. Powdery mildew, Erysiphe polygoni, Sphaerotheca fuliginea. These fungi are obligate plant parasites which grow vegetatively on the plant leaf surface, sending haustoria, structures which absorb food from the host, into epidermal cells. The white mildew seen on the leaf is a combination of vegetative mycelium and spores borne in chains on upright conidiophores.