WCN December 2019

l
m,
tility
generated over $15 in tax revenue
creation.2
Spending on export promotion in
2017 created 2,682 jobs.2
The Latest on
Disease
66% Resistant
Rootstocks
THIS ARTICLE IS
SPONSORED BY:
66% of the California
walnut crop was exported
in the 2017/18 crop year.
By CECILIA PARSONS walnuts.org | Associate Editor
Larger trees with orange band painted on shows test rootstock in a replant orchard infested with nematodes and
replant disorder. Two Chandlers on test rootstock are on either side of a Chandler on VX211 and clear performance
superiority of test rootstock is painfully obvious. All trees are same age in that row of three. All photos courtesy of
Cliff Beumel.
SIGNIFICANT PROGRESS IS
being January made 2018, Harry in M. Kaiser, the Cornell development University of
walnut rootstocks that possess resistance
to the major yield limiting diseases
and soil-borne pathogens.
“We are now working on putative
disease resistant walnut genotypes
which are being propagating to test in
large scale field trials to determine how
they perform compared to the greenhouse
evaluations, “ said Dan Kluepfel,
United States Department of Agriculture
(USDA)/Agricultural Research Service
(ARS) research scientist and principal
investigator of the walnut rootstock
development program.
“This is not just an academic pursuit.
1 California Agricultural Statistics Review 2016/2017 by CDFA
2 Economic Evaluation of the California Walnut Commission’s Export
Promotion Programs: An Analysis of the Direct and Indirect Impacts,
We have something in hand and in collaboration
with nurseries are moving
forward to place these rootstocks in
field trials.”
Disease-Resistant Rootstocks
Disease-resistant rootstocks for
commercial walnuts are a huge deal for
growers, said Cliff Beumel, a long time
walnut grower and nurseryman and
President of the fruit, nut and olive tree
nursery Agromillora located north of
Sacramento near Gridley.
“All growers eventually bump up
against one of these pressures,” Beumel
said of crown gall, Phytopthora and
lesion nematodes. “This is a real issue
right now in existing orchards.”
Most California walnut growers know
they need to choose rootstocks based
on their ability to resist or tolerate
various soil-borne diseases and nematodes,
even if pressure is low at the time
of planting. After the trees are planted,
there are few options for growers, who
find these pathogens, to control their
impact on tree health.
Significant walnut acres are planted
with seedling or clonal ‘Paradox”
rootstocks which are susceptible to the
soil-borne diseases, crown gall, root
lesion and root knot nematode and
Continued on Page 10
First 5 trees on left show the replant tolerant rootstock and the trees on right are standard Chandler on VX211.
8
West Coast Nut December 2019