How to Manage Pests

UC Pest Management Guidelines

Caneberries

Late Leaf Rust

Pathogen: Pucciniastrum americanum

(Reviewed 12/09, updated 12/09)

In this Guideline:


Symptoms and Signs

Late leaf rust infects red and purple raspberry and is not a systemic pathogen. As the name late leaf rust suggests, later in the season (beginning in July) many small rust spots are found on the older, lower leaves of raspberries. These spots first turn yellow and then brown. In severe cases plants can be defoliated, and the rust can also infect flowers and fruit. Yellow uredinia and powdery urediniospores form on the bottom sides of leaves. In fall, telia and teliospores appear as brown growth within existing uredinia.

Comments on the Disease

Because this pathogen's alternate host, white spruce (Picea glauca), is not common in coastal California where caneberries are cultivated, the fungus probably overwinters as mycelium within remaining canes and produces urediniospores in spring. These spring urediniospores then infect growing plants. Spores of P. americanum are spread by wind, and infection of leaves is favored by high relative humidity.

Management

As with yellow rust, any method that improves air circulation in the raspberry hedgerow is helpful in mitigating the spread and development of this disease. Also, the removal of infected floricanes and primocanes is useful in that it removes an important source of inoculum. The dry conditions in a macrotunnel greatly limit the infestation of late leaf rust, provided the tunnels are constructed before ideal conditions for infestation begin. In the Monterey Bay area, this generally means mid- to late July.

Common name Amount per acre R.E.I.‡ P.H.I.‡
(example trade name)   (hours) (days)

  Calculate impact of pesticide on air quality
 
When choosing a pesticide, consider its usefulness in an IPM program by reviewing the pesticide's properties, efficacy, application timing, and information relating to resistance management, honey bees, and environmental impact. Not all registered pesticides are listed. Always read the label of the product being used.
 
DELAYED DORMANT
 
A. FIXED COPPERS# Label rates 24 0
  MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M1)
  COMMENTS: For organically certified produce, check with your certifier for acceptable copper formulations.
 
FIRST BLOOM
 
A. FIXED COPPERS# Label rates 24 0
  MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M1)
  COMMENTS: For organically certified produce, check with your certifier for acceptable copper formulations.
 
B. PYRACLOSTROBIN+BOSCALID
  (Pristine) 18.5–23 oz 12 0
  MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) and Carboxamide (7)
 
C. PYRACLOSTROBIN
  (Cabrio) EG 14 oz 12 0
  MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
 
D. MYCLOBUTANIL
  (Rally) 40WSP 1.25–1.5 oz 24 0
  MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
  COMMENTS: Initiate applications as early as budbreak and continue at 10- to 14-day intervals. Shorter intervals may be used under heavy disease pressure. Do not apply more than 10 oz/acre per season.
 
E. TRIADIMEFON
  (Bayleton) 50DF 4 oz 12 1
  MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
  COMMENTS: For use on raspberries only. Apply in not less than 20 gal water/acre using ground equipment. Make additional applications at 4- to 6-week intervals as needed, not to exceed 7 applications in one year or 2 applications within the same 30-day period.
 
# Acceptable for use on organically grown produce.
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. 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: Caneberries
UC ANR Publication 3437

Diseases

  • S. T. Koike, UC Cooperative Extension, Monterey County
  • M. P. Bolda, UC Cooperative Extension, Santa Cruz County
  • W. D. Gubler, Plant Pathology, UC Davis
  • L. J. Bettiga, UC Cooperative Extension, Monterey County
Acknowledgment for contributions to Diseases:
  • E. J. Perry, UC Cooperative Extension, Stanislaus County

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