How to Manage Pests
UC Pest Management Guidelines
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 in color and not fully developed; kernels that develop normally and fill the shell cavity but are partially or totally wet, smelly, rancid, and dark colored; and kernels that fill the shell cavity but look abnormal—white and jellylike.
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.
UC IPM Pest Management Guidelines: Pistachio