Almond Disease Control Report
Beth L. Teviotdale, Extension Plant
Pathologist,
University of California Davis/Kearney Agricultural Center
John Edstrom, Farm Advisor, Colusa County
Almond trees are treated annually for protection against an array of
plant diseases. Along with the several diseases growers face, there is a list of
fungicides from which to choose. Making decisions about fungicide choice and treatment
timing for any given disease may have an effect on other diseases as well. Thus it is
important to select fungicides that are effective against diseases known to be in the
orchard and to apply them at the correct time.
Our objective with this research has been to evaluate various fungicide
programs and new fungicides for effectiveness against several diseases.
All the programs provided similar control of brown rot and shot hole.
The bloom sprays were applied later than planned, due to extended spring rains, thus the
single application intended for full bloom was not applied until late full bloom or early
petal fall. This later timing may account for the slightly poorer control of brown rot
found among these treatments. The single application of Break® + Ziram® at this time
provided adequate though not spectacular control of both brown rot and shot hole. This
most likely would not be a reliable practice over many years.
The experimental material AuxiGro® functions as a stimulant to the
plant’s natural defense mechanisms. Although AuxiGro® alone was ineffective in
controlling brown rot or shot hole, a half-rate of Rovral® combined with Auxigro® was as
effective as Rovral® alone. Materials such as Auxigro® are widely studied and we may see
more of their use in the future.
The new fungicide Indar® is an excellent brown rot material and also
has some efficacy against shot hole. This will be a good addition to the arsenal of
fungicides for almond disease control.
The leaf blight data are questionable this year. The rating system used
to assess disease appears to have been inadequate thus we are reluctant to express any
opinions based on this year’s experience.
Growers should plan a fungicide program that protects against brown rot
during bloom and shot hole, scab, leaf blight and perhaps anthracnose later in the season.
Trees are most susceptible to brown rot at full bloom so early timings should include a
spray at or near full bloom. Later applications are aimed at the other diseases. Late
bloom and post bloom fungicide choices should include at least one materials with a broad
spectrum of activity.
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