WCN Dec e

Navel Orangeworm Rejects on the Rise
Double down on almond IPM, starting with winter
sanitation, to reduce damage.
By VICKY BOYD | Contributing Writer
Timely harvests are part of a navel orangeworm integrated management program. The end
use, whether for meats or for in-shell, also will affect harvest timing (photo by V. Boyd.)
While the amount of Nonpareil almond rejects due
to navel orangeworm (NOW) damage varies from
season to season, Blue Diamond Growers has noted
a concerning uptick over the past 10-plus years. With the
upward trend comes opportunity losses from reduced or no
grower premiums.
University of California Cooperative Extension farm advisors
and Blue Diamond staff point to not one, but a combination
of factors that likely are responsible for the increasing
rejects.
“It’s hard to say exactly what’s going on,” said Jhalendra
Rijal, UCCE IPM advisor for Stanislaus, San Joaquin and Merced
counties. “It could be multiple factors at play.”
Among potential contributors are drought conditions, larger
nut crop acreage that provides increased continuous hosts,
the availability and cost of polling crews for winter sanitation,
and pesticide resistance.
As a result, Extension and industry representatives recommend
growers double down on their IPM practices, which
start with foundational winter sanitation. Proper timing of
the other IPM practices is also crucial, whether it is hanging
monitoring traps in the spring, putting out mating disruption
dispensers, applying hull split sprays or harvesting.
Rejects Up in 2021
So far this season, Nonpareil overall reject levels are running
about 1.75%, second only to the “train wreck” of 2017
and 2018, said Mel Machado, Blue Diamond vice president
Complete Walnut and Pecan
Hulling And
Drying Systems
209-754-9636
3474 Toyon Circle, Suite 333
Valley Springs, CA 95252
of member relations. In
the past, about 80% of the
rejects could be attributed
to NOW damage. But
that’s not the case anymore.
While NOW still comprises
the bulk of the rejects at
53%, he said other problems,
such as brown hole, are on
the rise.
“NOW is still the primary
problem out there, but
primary is a relative term,”
Machado said. Rather than
looking at average reject
levels, he said he prefers to
look at how much of the
crop goes into the co-op’s
quality programs.
The navel orangeworm moth
itself does not feed on almonds.
Females lay eggs on mummy nuts
or on nuts after hull split begins.
After they hatch, first-instar larvae
bore into the nut meat (photo
courtesy USDA-ARS.)
Based on the amount of the Blue Diamond crop run as of
late October, about one-third failed to make grade and was
considered standard. Broken down, the northern production
area was running 38%, the central 25.7% and the south 44%.
“That’s stunning, 44%,” Machado said. “Even in 2017, it was
37%.”
When Machado compared the crop going for meats to that
destined for in-shell, the differences were glaring.
Only 12% of in-shell failed to make grade. He attributed it
to varieties that have tighter seals, making them less susceptible
to NOW. Growers also are more aware of reject levels for
the in-shell market and manage accordingly.
The Foundation: Winter Sanitation
At the heart of NOW management is winter sanitation,
which not only removes mummies in which larvae overwinter
but also eliminates egg laying sites for the first NOW flight in
the spring.
Franz Niederholzer, UCCE farm advisor for Colusa, Sutter
and Yuba counties, recommended surveying orchards for
mummies on or before Jan. 15. Count the mummies on 20
representative trees and average the results. This should be
done for each variety, regardless of shell thickness or seal,
Continued on Page 8
6 West Coast Nut December 2021