UC IPM: UC Management Guidelines for Cane and Leaf Rust on Caneberries

UC Pest Management Guidelines

Caneberries

Cane and Leaf Rust

Pathogen: Kuehneola uredinis

(Reviewed 5/08, updated 5/08)

In this Guideline:

Symptoms
Comments on the disease
Management

Cane and leaf rust occurs on some blackberry cultivars, especially trailing varieties such as ollalieberry. The first symptom of cane and leaf rust is lemon yellow pustules (uredinia) that split the bark of the fruiting canes of susceptible blackberries. Spores from these pustules (urediniospores) infect leaves and produce small yellow pustules (uredinia) on the underside of leaves during early summer. Defoliation can occur if infection is severe. Buff-colored telia develop among the uredinia on leaves in early fall.

It is important not to confuse this common blackberry disease with the less common but far more damaging orange rust, which causes plants to produce many small, weak shoots from the base of the plant.

On susceptible blackberry varieties leaf defoliation can be severe and result in the loss of plant vigor. Normally cane and leaf rust doesn't infect the fruit but masses of spores falling on fruit can render it unmarketable. Raspberries are hosts, but occurrence of this disease on this crop is rare. Wet spring conditions will favor disease development. The fungus overwinters on canes as mycelium or latent uredinia. Cane and leaf rust can be distinguished from orange rust by the presence of yellow pustules (uredinia) on both the canes and leaves. Orange rust has orange pustules on leaves only.

Control is best achieved by using both cultural methods to reduce pathogen sources in combination with fungicides. Remove and dispose of fruit canes soon after harvest to reduce inoculum sources. Highly susceptible varieties with a history of this disease should receive applications of protective fungicides before the onset of disease symptoms and pathogen signs. A recommended spray control program is a winter application of lime sulfur followed by fixed copper applied at green tip stage and then a treatment at bloom.

Organically Acceptable Methods
Removal of fruited canes after harvest and sprays of lime sulfur or some fixed coppers are acceptable management tools in an organically certified crop.

Common name

Amount/Acre

R.E.I.+

P.H.I.+

(trade name)

(hours)

(days)

When choosing a pesticide, consider the general properties of the fungicide as well as information relating to environmental impact.

DORMANT

LIME SULFUR#

8 gal/100 gal water

MODE OF ACTION GROUP NAME (NUMBER¹): Multi-site contact (M2)

COMMENTS: Apply in 200 gal water/acre.

DELAYED DORMANT

FIXED COPPERS#

Label rates

MODE OF ACTION GROUP NAME (NUMBER¹): Multi-site contact (M1)

COMMENTS: Not all copper compounds are approved for use in organic production; be sure to check individual products.

LIME SULFUR#

8 gal/100 gal water

MODE OF ACTION GROUP NAME (NUMBER¹): Multi-site contact (M2)

FIRST BLOOM

FIXED COPPERS#

Label rates

MODE OF ACTION GROUP NAME (NUMBER¹): Multi-site contact (M1)

COMMENTS: For organically certified produce, check with your certifier for acceptable copper formulations.

MYCLOBUTANIL

(Rally) 40WSP

1.25–1.5 oz

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/season.

PYRACLOSTROBIN/BOSCALID

(Pristine)

18.5–23 oz

MODE OF ACTION GROUP NAME (NUMBER¹): Quinone outside inhibitor (11) and Carboxamide (7)

COMMENTS: Restricted entry interval is 12 hours. To limit the potential for development of resistance, do not apply more than 4 application of this or other Group 7 and 11 fungicides per season.

PYRACLOSTROBIN

(Cabrio) EG

14 oz

MODE OF ACTION GROUP NAME (NUMBER¹): Quinone outside inhibitor (11)

COMMENTS: Restricted entry interval: 24 hours. Do not make more than two sequential applications before alternating to a product with a different mode of action Group number.

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.

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 fungicide with a different mode of action Group number.

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
E. J. Perry, UC Cooperative Extension, Stanislaus County
W. D. Gubler, Plant Pathology, UC Davis
L. J. Bettiga, UC Cooperative Extension, Monterey County

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How to Manage Pests

UC Pest Management Guidelines

Caneberries

Cane and Leaf Rust

Pathogen: Kuehneola uredinis

SYMPTOMS

COMMENTS ON THE DISEASE

MANAGEMENT

PUBLICATION