How to Manage Pests

UC Pest Management Guidelines

Walnut

Bactericide and Fungicide Efficacy

(Reviewed 6/17, updated 6/17)

In this Guideline:


BACTERICIDE EFFICACY

Material Resistance risk (FRAC#)1 Walnut blight2 Phytotoxicity Anthracnose Botryosphaeria blight***
Copper+mancozeb (Manzate,Dithane) low (M1+M3) ++++ NP ++++ ++(+)
Kasumin+copper* low (24+M1) ++++ NP ---- ----
Kasumin+mancozeb* low (24+M3) ++++ NP ---- -----
Bordeaux2 low (M1) +++ NP ---- ----
Fixed coppers2 medium (M1) +++ ++3 ---- ----
Kasumin* high (24) +++ NP ---- ----
Actinovate low (biological) ++ NP ---- ----
Copper+mancozeb+surfactant4 low (M1+M3) + NP ND ND
K-Phite low (33) + + ND ++++
Fontelis high (7) ---- ---- ND +++
Luna Experience medium (3/7) ---- NP ++++ ++++
Luna Sensation medium (7/11) ---- NP ND ++++
Luna Privilege high (7) ---- NP ND ND
Merivon medium (7/11) ---- NP ++++ ++++
Pristine medium (7/11) ---- NP ++++ ++++
Ph-D medium (19) ---- NP ++++ +++
Quadris Top medium (3/11) ---- NP ++++ +++
Quash high (3) ---- NP ++++ ++++
Rhyme high (3) ---- NP ND ++++
Tebucon, Teb, Toledo high (3) ---- NP ND +++
Quilt Xcel medium (3/11) ---- NP ++++ ----
Viathon medium (3/33) ND ND ND +++
Organic treatments
Zinc sulfate+Copper +Hydrated lime
(Zinc Bordeaux)
low (M1) +++ NP ---- ND
Regalia low (natural product) ++ NP ND ----
Regalia+Copper low (natural product) ++ NP ---- ----
Blossom Protect low (biological) +/++ NP ---- ----
Serenade low (44) + NP ND ----
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** Not registered, label withdrawn or inactive in California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. 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.
4 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: Not all indicated timings may be necessary for disease control.

Disease Catkin emergence Terminal bud break 7-10 day intervals April May June July August October November (1st week)
Anthracnose ---- ---- ---- ++4 +++ ++ ---- ---- ---- ----
Botryosphaeria blight ---- ---- ---- + ++ +++ +++ ++ + +
Walnut blight 1,2,3 ++ +++ +++ +++ ++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.
4 Make the first application when the size of the expanding leaves is about half of its final size. This first application stage is critical.

[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. 2017. Efficacy and Timing of Fungicides, Bactericides, and Biologicals for Deciduous Tree Fruit, Nut, Strawberry, and Vine Crops (PDF)

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