Symptoms and Signs
Stigmatomycosis of pistachio is characterized by the wet, smelly, rancid, slimy appearance of the kernel. There are three major symptoms of stigmatomycosis: small kernels that are dark and not fully developed; kernels that develop normally and fill the shell cavity but are partially or totally wet, smelly, rancid, and dark; and kernels that fill the shell cavity but look abnormal: white and jellylike.
Comments on the Disease
The yeasts that caused stigmatomycosis are associated with hemipteran insects (true bugs) in the families Pentatomidae (stink bugs) or Coreidae. Hemiptera are common pests in pistachio orchards. Switching from sprinkler irrigation to drip, microjets, or flood irrigation reduces damage from bugs as well as stigmatomycosis. Feeding by plant bugs can also damage the kernel, causing kernel necrosis, a brown-to-black distinct lesion that sometimes shows concentric rings.
Fungicide applications are not effective in controlling stigmatomycosis; however, an insecticide spray to control STINKBUGS and LEAFFOOTED PLANT BUGS has been shown to reduce the incidence of stigmatomycosis.