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UC Pest Management Guidelines


Artichoke

Powdery Mildew

Pathogens: Leveillula taurica, Erysiphe cichoracearum

(Reviewed 1/07, updated 6/09)

In this Guideline:


SYMPTOMS AND SIGNS

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.

COMMENTS ON THE DISEASE

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.

MANAGEMENT

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)

  Calculate impact of pesticide on air quality
When choosing a pesticide, consider information relating to environmental impact. Not all registered pesticides are listed. Always read label of product being used.
 
A. AZOXYSTROBIN
  (Quadris) 11–15.4 fl oz 4 0
  MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
  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.
 
B. MYCLOBUTANIL
  (Rally) 40WSP 2–4 oz 24 3
  MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
  COMMENTS: 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 REI exceeds the PHI. The longer of 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 (for more information, see http://www.frac.info/). Fungicides with a different group number are suitable to alternate in a resistance management program. In California, make no more than one application of fungicides with mode of action Group numbers 1,4,9,11, or 17 before rotating to a fungicide with a different mode of action Group number; for fungicides with other Group numbers, make no more than two consecutive applications before rotating to a fungicide with a different mode of action Group number.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

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

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