How to Manage Pests

UC Pest Management Guidelines

Walnut

Efficacy of Bactericides and Treatment Timings for Walnut Blight

(Reviewed 3/10, updated 1/16)

In this Guideline:


BACTERICIDE EFFICACY

Material Resistance risk (FRAC#)1 Walnut blight2 Phytotoxicity Anthracnose Botryosphaeria blight***
Actinovate low (biological) ++ NP ---- ----
Bordeaux2 low (M1) +++ NP ---- ----
Fixed coppers2 medium (M1) +++ ++3 ---- ----
Fontelis high (7) ---- ---- ND +++
Copper-mancozeb (Manzate/Dithane) low (M1/M3) ++++ NP ---- ++
Copper-mancozeb–surfactant4 low (M1/M3) + NP ---- ----
Kasumin* high (24) +++ NP ---- ----
Kasumin-copper* low (24/M1) ++++ NP ---- ----
Kasumin-mancozeb* low (24/M3) ++++ NP ---- -----
K-Phite low (33) +? + ND ++++
Luna Experience medium (3/7) ---- NP ++++ +++
Luna Sensation medium (7/11) ---- NP ND ++
Merivon medium (7/11) ---- NP ND ++++
Pristine medium (7/11) ---- NP ++++ +++
Quadris Top medium (3/11) ---- NP ND +++
Quash high (3) ---- NP ND ++++
Tebucon/Teb/ Toledo high (3) ---- NP ND +++
Viathon medium (3/33) ND ND ND +++
Quilt Xcel medium (3/11) ---- NP ++++ ----
Regalia low (natural product) ++ NP ND ----
Regalia-Copper low (natural product) ++ NP ---- ----
Blossom Protect low (biological) +/++ NP ---- ----
Serenade low (44) + NP ND ----
Zinc-Copper Bordeaux low (M1) +++ NP ----
Rating: ++++ = excellent and consistent, +++ = good and reliable, ++ = moderate and variable, + = limited and erratic, ---- = ineffective, NP = not phytotoxic, and ND = no data.
*Registration pending in California
** Not registered, label withdrawn or inactive in California
*** Research is ongoing to determine the most efficacious materials and the optimum timing of treatments for management of Botryosphaeria blight of walnut.
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 fungicide with a different mode-of-action Group number.
2 Copper resistance occurs within sub-populations of Xanthomonas arboricola pv.juglandis.
3 Phytotoxicity of fixed coppers can be reduced with the addition of lime or agricultural oils to the tank mixture.
5 A single application with a surfactant is not recommended because of build up of populations on buds that may increase disease in subsequent years.

WALNUT: TREATMENT TIMING

Note: Timings listed are effective but not all may be required for disease control. Timings used will depend upon orchard history of disease and weather conditions each year.

Disease Catkin emergence Terminal bud break 1 week after bud break 7-10 day intervals1 May2
Walnut blight3 ++ +++ +++ ++1 +
1 A temperature-leaf wetness model (e.g., XanthoCast) is available for determining optimum timing of bactericide applications.
2 Late spring rains are less conducive to disease, provided bloom is not delayed by low chilling.
3 Male and female flowers are susceptible beginning with their emergence, depending on wetness and temperatures conducive to disease development.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Walnut
UC ANR Publication 3471

General Information

Adaskaveg, J. E., B. A. Holtz, T. J. Michailides, and W. D. Gubler. 2015. Efficacy and Timing of Fungicides, Bactericides, and Biologicals for Deciduous Tree Fruit, Nut, Strawberry, and Vine Crops (PDF)

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