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UC Pest Management Guidelines


Ringspot lesions are made up of a series of concentric rings.

Cole Crops

Ringspot

Pathogen: Mycosphaerella brassicicola

(Reviewed 6/07, updated 11/08)

In this Guideline:


SYMPTOMS AND SIGNS

In California, this disease occurs primarily on Brussels sprouts. Symptoms consist of circular leafspots (0.5 inch in diameter) that range in color from light brown to black. With time these spots develop concentric rings much like a target pattern. Small spherical fruiting structures may also be observed within the leafspots. If disease is severe, some defoliation may take place. This pathogen may also infect the sprouts, causing dark lesions on outer leaves.

COMMENTS ON THE DISEASE

The infection and disease development are favored by cool, moist conditions. Spores produced by this pathogen are spread by wind. Mycosphaerella brassicicola will persist in soil on infected plant residues only. There is some evidence that this pathogen may be carried on seed.

MANAGEMENT

Incorporate plant residues so that infected material decomposes fully. Remove volunteer plants that may be infected. Plant disease-free transplants. If ringspot is a problem in the area, use a protectant fungicide before infection takes place.

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. CHLOROTHALONIL
  (various products) Label rates 12 7
  MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M5)
  COMMENTS: Use at 7- to 10-day intervals; multiple applications are needed (up to 4 maximum).
 
+ 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.
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. For fungicides with mode of action Group numbers 1, 4, 9, 11, or 17, make no more than one application 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 fungicide with a different mode of action Group number.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Cole Crops
UC ANR Publication 3442
Diseases
S. T. Koike, UC Cooperative Extension, Monterey County
K. V. Subbarao, Plant Pathology,UC Davis, Salinas

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