mar-apr-2018 - page 34

Taking Control of Botryosphaeria
in California Walnut Orchards
Botryosphaeria are a group of fungal
pathogens that have beenwell-known
for decades in the California pistachio
industry, with initial discovery in 1984
and signi cant production loss to the
disease in the late 1990s. However,
Bot pathogens have emerged as
a growing challenge to walnut tree
health and yields in California in the
past three to four years. In walnuts,
Bot can easily spread from tree to
tree by wind or water, and spores
germinate with a quarter-inch of rain
or as little as 90 minutes of exposure
to water.
The disease has a multi-season
impact on orchards. Bot infects and
damages the current year’s fruit, and
also the fruit wood that will produce
fruit the following year.
“In some mature walnut orchards,
we’ve seen yield declines of 25
percent or more in the rst year,
with additional declines the second
year and potentially devastating
impacts to the health of trees in
the orchard,” said Chuck Gullord,
a technical sales representative
for Bayer.
Botryosphaeria spores germinate
and enter the tree through existing
wounds or scars, such as those
from pruning, leaf and fruit drop or
bud scars. Research conducted by
the University of California in 2014
found that untreated wounds can
be susceptible to infection from
Bot fungi for extended periods. For
example, pruning wounds in medium
to large branches can be infected
for at least four months after the
pruning cut is made.
While walnut scale damage
has historically not been
considered a significant
economic threat to walnut
production, the lesions on
trunks and old branches
caused by scale are a key
entry point for Bot infection.
Walnut trees with scale
infestations are 60 to 70
percent more prone to
Bot infection.
Identi cation of Bot infection in walnut trees can be
dif cult compared to identifying the disease in pistachio
and other trees, because other diseases such as Walnut
blight show similar symptoms. The symptoms can
also be confused with frost damage or winterkill in some
circumstances.
BOTRYOSPHAERIA
ADVERTORIAL
© 2018 Bayer CropScience LP, 2 TW Alexander Drive, Research Triangle Park, NC 27709. Bayer, the Bayer Cross, Luna,
Luna Experience, Luna Sensation, and Movento are registered trademarks of Bayer. Luna and Movento are not registered for
use in all states. Always read and follow label instructions. For additional product information, call toll-free 1-866-99-BAYER
(1-866-992-2937) or visit our website at www.CropScience.Bayer.us.
“Walnut trees with scale
infestations are
60 to 70
percent more
prone to Bot infection.”
Chemical control
programs are highly
effective in controlling
Bot fungi as well as
scale and other
damaging insects that
allow disease to spread.
Bayer provides several
solutions for walnut growers.
Luna Sensation® and Luna
Experience® fungicides are
highly effective in controlling
Bot fungi, and Movento®
insecticide provides effective
control of scale and other
major insects and mite pests.
IMPORTANT: This bulletin is not intended to provide adequate information for use of these products. Read the
label before using these products. Observe all label directions and precautions while using these products.
Yield (lb./A) and percent jumbos in a university/grower large plot trial at Modesto, CA, 2014. Andy
Alderson (Modesto Junior College) and Dr. Themis Michailides. Tulare variety, planted 2004. Applications
on 4/16, 5/15, 6/25, 7/25 and 10/30. Harvest on 9/29. Plots: 11 rows, 2 rows harvested per plot.
5,888
7,055
6,583 6,638
0
1,000
2,000 Net Weight (lb./A)
3,000
4,000
5,000
6,000
7,000
8,000
Untreated Luna Sensation®
Program
Competitor
Program
Luna Experience®
Program
92.1%
Jumbos
95%
Jumbos
91.2%
Jumbos
84.1%
Jumbos
In addition, walnut
trees in a university/
grower large plot trial
treated with Luna
Experience
®
and
Luna Sensation
®
programs delivered
1,167 and 695
pounds per acre of
increased walnut
yields compared to
untreated controls.