Page 48 - Grapevine March-April 2020

Around The Vineyard
Merlot research vineyard in the San Joaquin
Valley—where more than half of all California
grapes are grown— that indicated mechanical
pruning “reduced labor costs by 90%, resulted in
increased grape yields and had no impact on the
grape berry’s anthocyanin content.”
Kaan Kurtural, UC Cooperative Extension special-
ist in the UC Davis Department of Viticulture and
Enology; and George Zhuang, UCCE viticulture advi-
sor in Fresno County; conduct conference panels
and webinars about the process, which they say
is the future of pruning for operations of 150–300
acres.
So keep in mind as you strategize production
growth and processes, “one of the greatest dis-
advantages to cane pruning in our future shift to
mechanization is that it cannot be easily machine-
pruned,” Westover said.
Questions of the Advisor
Since Westover consults for dozens of vineyards
east of the Rocky Mountains through his onsite vis-
its and victual academy, we asked him to provide
answers to the top three questions he gets regard-
ing pruning. They are:
1. When should I start pruning?
A: Depending on vineyard size, time and labor,
if a grower in the Northern Hemisphere uses
pre-pruning or partial pruning, I encourage
them to start in January and move to final
pruning at a time that allows them to complete
it prior to budburst. So, for example, a small
grower may be able to prune in a week and
can start the process 10-to-14 days before the
historical average budburst date in their area.
Larger vineyards obviously need more time and
may be pruning steady until budburst.
2. Do I need to protect pruning wounds from
GTDs?
A: Fungal diseases associated with GTDs are
primarily spread by splashing rain. Therefore,
it’s important not to prune when it’s raining
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or when rain is predicted within the next few
days—I advise my growers to wait until after
the rain. In some cases, registered fungicides
can be applied to protect pruning wounds from
infection, such as Topsin M—check your state
registry status. If pruning wounds have healed
over, or if no rain is predicted, then protective
sprays can be avoided. There are also products
available now that can be painted over the top
of larger pruning wounds to create a physical
boundary against pruning wounds, such as
VitiSeal.
3. What if I don’t finish before budburst?
A: Ideally, all final pruning will be completed a
week or so before budburst. When shoots begin
to grow, they first emerge on the most distal
part of a cane, which is referred to as “apical
dominance” of shoots across a cane. Some
growers intentionally hold off final pruning until
the onset of budburst on distal bud positions,
as this can delay the budburst of the lower buds
retained as spurs near the cordon. This small
delay in budburst can result in the avoidance
of a late spring freeze by 7-to-14 days, depend-
ing on site and variety. However, if a grower
doesn’t complete final pruning before the
shoots on the distal nodes reach greater than
two inches in length, the lower bud positions
can lose fruitfulness. The bottom line: pruning
needs to be completed by bud swell—and not
later.
Education, Sterilization, and Clean-Up
Ensures Successful Results
Many vineyard managers hire crews with prun-
ing experience, while some do a crash course each
season with trusted volunteers. In either scenario,
Westover said, you need to ensure people do what
your vines require.
“Cut-and-paste pruning strategies won’t address
the needs of each block. A pruning crew is only
as good as its instructor, and it’s often necessary
to have a lot of supervision the first few days of
pruning—and again any time the pruning strat-
egy changes between vineyard blocks,” he said.
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