The Crush August - 1

theCrush
Volume 49 | Issue 8 | August 2023
FEATURE STORY
Preparing for Harvest 2023
BEST PRACTICES TO PREVENT PEST/VIRUS SPREAD
Article by Ted Rieger
Due to early season cool and rainy weather, growers
predict a harvest start of two to four weeks later than last
year. While this allows more time to prepare for harvest
by scheduling labor, equipment, and logistics, a later
harvest could also increase risks to crop yield and quality
from late-season heat waves, wildfire smoke, or early
fall rains. Preliminary crop load predictions are variable
and highly site-specific. In the San Joaquin Valley, some
growers report higher than normal crop sizes. In other
locations, spring weather resulted in a poor fruit set that
could reduce crop loads for some varieties. In general,
there are indications the 2023 California winegrape crop
could be closer to " average, " around 4 million tons, after
three consecutive years of short crops below 4 million
tons. High rainfall totals contributed to heavy canopy
growth in many locations that may require pre-harvest
vine row hedging to enable better access for harvest
equipment and workers.
Equipment Sanitation
As the use of mechanical harvesters increases, and
as growers and custom harvesters move
equipment to vineyards over a wider
geographic area, the risk of moving vineyard
pests from infected to non-infected vineyards
increases. Although washing mechanical
harvesters is a common practice at the end of
a daily harvest shift, growers are advised to
consider more frequent and more thorough
sanitizing practices to prevent the spread
of mealybugs that vector leafroll viruses,
especially when working in vineyards with
known or suspected virus and mealybug
populations. The spread of mealybugs
through vineyard management operations
from workers, equipment,
vehicles, and tools is
a concern year-round,
particularly with the vine
mealybug, that can be
present in vineyards year-round.
Dr. Stephanie Bolton, Research and Education Director
for the Lodi Winegrape Commission (LWC) coordinated
the writing and publication of the workbook, " What
Every Winegrower Should Know: Viruses. " As Bolton
explained in a recent LWC blog post: " Machine harvest
is a high-risk activity when it comes to mealybug and
virus infections. Both the mealybug populations and
the amount of leafroll virus present in a grapevine (virus
titer level) are at their peak during harvest. " Bolton
noted that most mechanical harvesters are not cleaned
well between different vineyard blocks. As such, she
said, " We advise scheduling harvest jobs for each day
from the least infested/infected vineyards to the most
infested/infected vineyards. " This information should
be communicated and planned with the harvest crew.
If a grower works with a custom harvester service or a
vineyard management company, scheduling and cleaning
procedures can be written into the contract agreement,
with the negotiation of possible added costs.
Mechanical harvesters being washed and serviced between shifts.
Photo: Ted Rieger
The Crush August

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