By Mike Matheron, UA Extension Plant Pathologist

Chile peppers are great to eat and an important crop in Arizona. Production occurs primarily in southeastern Arizona where favorable growing conditions exist. 

A disease of peppers called Phytophthora blight can cause significant plant death and yield loss. The pathogen that causes this disease, Phytophthora capsici, resides in the soil and becomes active when the soil is overly wet. The spread of the pathogen and disease development are related to the duration and intensity of summer rainfall events.

Initial infection of plants occurs on roots and stems of plants at the soil surface. Successive rainfall events and sustained high levels of humidity lead to infections on the upper parts of plants, including the leaves, stems, and pepper fruit.

This pathogen is closely related to Phytophthora infestans, the organism responsible for the devastating Irish potato famine that occurred around 1850.

Successful management of Phytophthora blight includes measures to minimize accumulation of excess water in pepper fields, plus the additional applications of fungicides when favorable disease development conditions exist. 

Effective fungicides include Ridomil Gold, Revus, Presidio, Ranman, and others.

Contact Matheron: (928) 726-6856 or matheron@ag.arizona.edu.