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 acervuli distinguishes 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 and this is probably the most important source of initial inoculum. Infection and disease development are enhanced by very wet conditions. 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. There is still some debate as to whether or not this fungus is seedborne.

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.

Organically Acceptable Methods
Cultural controls are acceptable for use on organically grown produce.

Common Name		Amount/Acre
(trade name)
A.	COPPER HYDROXIDE	Label rates
	MODE OF ACTION: A multi-site contact (Group M)1 inorganic fungicide.
	COMMENTS: Copper sprays are not very effective. Apply as a protectant spray at 10–14 day intervals. Rate often depends upon disease severity. A suitable agricultural spray oil is recommended for use with some copper formulations. Consult label for specific application guidelines.
1	Group designations are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of actions. Fungicides with a different group designation are suitable to alternate in a resistance management program. For more information, see www.frac.info/.

PUBLICATION

UC IPM Pest Management Guidelines: Spinach
UC ANR Publication 3467
Diseases
S. T. Koike, UC Cooperative Extension, Monterey Co.
M. LeStrange, UC Cooperative Extension, Tulare Co.
F. F. Laemmlen, UC Cooperative Extension, Santa Barbara Co.

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