WALNUT: BACTERICIDE AND FUNGICIDE EFFICACY – CONVENTIONAL

WALNUT: BACTERICIDE EFFICACY – BIOCONTROLS AND NATURAL PRODUCTS

Rating: 5 = excellent and consistent, 4 = good and reliable, 3 = moderate and variable, 2 = limited and/or erratic, 1 = minimal and often ineffective, 0 = ineffective, NL = not on label, 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** Not registered, label withdrawn or inactive in California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 and kernel mold of walnut. Fungicides rated for kernel mold may have to be mixed (e.g., Merivon -FC 7/11 and Teb-FC 3) and rotated to another fungicide (e.g., Rhyme - FC-3). This mixture rotation is ‘+++’.

¹ Code 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 Code number are suitable to alternate in a resistance management program. In California, make no more than one application of fungicides with mode-of-actions (MOA) with high resistance risk before rotating to a fungicide with a different MOA (Code number); for other fungicides, make no more than two consecutive applications before rotating to fungicide with a different MOA (Code number).

² Copper resistance occurs within sub-populations of Xanthomonas arboricola pv. juglandis.

³ Phytotoxicity may occur. For fixed coppers, injury can be reduced by 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: 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.

Rating: 3 = most effective, 2 = moderately effective, 1 = least effective, and 0 = ineffective

¹ Make the first application when the size of the expanding leaves is about half of its final size. This first application stage is critical.

² Timing for kernel mold is based on a mixture rotation of Merivon (FC 7/11) and Teb (FC 3) followed by Rhyme (FC-3) at the timings indicated. This mixture rotation is ‘+++’ based on the ratings in the efficacy table above.

³ A temperature-leaf wetness model (e.g., XanthoCast) is available for determining optimum timing of bactericide applications.

⁴ Late spring rains are less conducive to disease, provided bloom is not delayed by low chilling.

⁵ Male and female flowers are susceptible beginning with their emergence, depending on wetness and temperatures conducive to disease development.