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spray a week after that. “It is a very
aggressive program. You are going to
treat it differently [than if you have low
disease pressure].”
He added that regardless of pressure
levels, growers will want to get a spray
on ahead of rain events. “That doesn’t
change,” he said. “The advantage of
knowing inoculum levels ahead of time
is really more about how early you start
and how aggressive you are with those
first two sprays.”
If treating for walnut blight, growers
should consider utilizing Kasumin in
combination with copper or mancozeb,
according to UCCE guidelines.
Kasumin, which was registered for use
in walnuts in March of 2018, offers
excellent and consistent efficacy when
applied with either copper or mancozeb,
according to UCCE research. The
product also has a unique mode of action,
providing an excellent rotational
material for resistance management.
Milliron advised growers to follow
label directions when spraying for walnut
blight and to rotate chemistries to
avoid the build-up of resistance.
“If the effectiveness of the copper-mancozeb
combination was lost
due to resistance, it would be an incredibly
tough hit to the industry, particularly
in the Northern Sacramento Valley
where rainfall levels are the greatest,”
Milliron wrote in a Sacramento Valley
Orchard Source article in 2018.
Winter Weed Control
Like walnut blight programs, winter
weed control programs require a good
understanding of the pressure in an
orchard. According to a Sacramento
Valley Orchard Source article from Milliron
and UCCE Weed Specialist at UC
Davis Brad Hanson, that understanding
often comes from past observances and
a fall weed survey. Documenting weed
discovery and escapes is also advised to
help growers understand what worked
and what didn’t in last year’s program
and to help in devising a change in
strategy if need be.
“I think it is really important to be
smart about understanding the weed
problem you are trying to resolve,”
Hanson said. “That includes properly
identifying the weed and having some
idea of its biology, such as when does it
come up versus when are my interventions.”
In developing orchards, UC Davis
weed management guidelines say it is
important to maintain a weed-free strip
at least 30 inches from the trunk of
trees to prevent weeds from competing
with trees for water and nutrients. In
established orchards, weed control is
less about removing competition for
water and nutrients, although that remains
a consideration, and more about
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