How to Manage Pests
UC Pest Management Guidelines
Initial symptoms of anthracnose are small, circular, water‑soaked lesions on both young and old leaves. Lesions later enlarge, turn brown to tan in color, and become thin and papery. In severe cases, lesions coalesce and result in severe blighting of foliage. In all cases, tiny black fruiting bodies (acervuli) form profusely in diseased tissue and are a characteristic feature of the disease. The presence of acervulidistinguishes anthracnose from Cladosporium and Stemphylium leaf spot diseases, both of which also form circular lesions.
Anthracnose has occurred sporadically in California since first detected in the state in 1993. When the pathogen is present, spores are spread from plant‑to‑plant by splashing water from rains or sprinklers. The fungus survives in infected plant debris as dormant mycelium. However, seedborne inoculum is the most important source of initial inoculum. Infection and disease development are enhanced by very wet conditions; therefore this disease is more often seen if spring rains are common. The heavy canopy of densely planted spinach retains much moisture and particularly favors disease development on the lower leaves. Epidemics are usually more severe in fields with low fertility.
Use disease-free seed. Reduce leaf moisture by avoiding sprinkler irrigation if possible. Be sure spinach fields are adequately fertilized. Resistant varieties are being developed by plant breeders. Copper fungicides have been used to slow epidemics, but they are generally ineffective, particularly under very wet conditions.
UC IPM Pest Management Guidelines: Spinach