UC IPM: UC Management Guidelines for Powdery Mildew on Artichoke

UC Pest Management Guidelines

Artichoke

Powdery Mildew

Pathogens: Leveillula taurica, Erysiphe cichoracearum

(Reviewed 1/07, updated 1/07)

In this Guideline:

Symptoms
Comments on the disease
Management

Two types of powdery mildew infect artichokes. Leveillula taurica is more commonly found and primarily colonizes the undersides of older leaves. Careful examination of leaf undersides reveals spores produced singly or in very short chains; however, the profuse white hairs of the leaf may obscure this sign. Severely infected leaves will turn yellow, then brown. With time the brown leaves may collapse and dry up. Leveillula infects only the older leaves; the younger leaves escape infection until they mature.

Powdery mildew caused by Erysiphe cichoracearum causes less severe symptoms. The flat, low-growing white to gray mycelia and spores of this fungus develop on the outside of flower bracts and on upper surfaces of both young and old leaves. The fungus produces abundant spores in long chains. Underlying tissue will turn brown.

Spores are dispersed by wind. Reports suggest that L. taurica from artichoke may be a different race than the L. taurica that occurs on tomato and other hosts.

If you see early symptoms, check weekly to monitor progress of the disease. Fungicides are not needed unless the disease becomes severe.

Common name

Amount/Acre

R.E.I.+

P.H.I.+

(trade name)

(hours)

(days)

When choosing a pesticide, consider information relating to environmental impact.

AZOXYSTROBIN

(Quadris)

11-15.4 fl oz

MODE OF ACTION: A Qol (Group 11)¹ fungicide

COMMENTS: Do not apply more than one application before alternating with a fungicie that has a different mode of action group number. Do not make more than 4 applications/acre/crop year. Do not apply more than 2.88 qt (1.5 lb a.i.)/acre/crop year.

MYCLOBUTANIL*

(Rally) 40WSP

2–4 oz

MODE OF ACTION: A DMI (Group 3)¹ triazole fungicide.

COMMENTS: Check with your county agricultural commissioner about the availability of this material under a Section 18 registration. Do not apply more than 0.4 lb/a.i./acre/year or exceed 4 applications/year.

+	Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) is the number of days from treatment to harvest. In some cases the R.E.I. exceeds the P.H.I. The longer of these two intervals is the minimum time that must elapse before harvest.
*	Permit required from county agricultural commissioner for purchase or use.
¹	Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of actions. Fungicides with a different group number are suitable to alternate in a resistance management program. For more information, see http://www.frac.info/.

UC IPM Pest Management Guidelines: Artichoke
UC ANR Publication 3434
Diseases
S. T. Koike, UC Cooperative Extension, Monterey County
Acknowledgment for contributions to the disease section:
S. Colbert, Griffin Corp., Valdosta, GA

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How to Manage Pests

UC Pest Management Guidelines

Artichoke

Powdery Mildew

Pathogens: Leveillula taurica, Erysiphe cichoracearum

SYMPTOMS

COMMENTS ON THE DISEASE

MANAGEMENT

PUBLICATION