Winter 2021 - 37

DISEASE
" Our efforts complement each other so what we can
accomplish as a group is greater than the sum of its parts, "
Iezzoni said. " Sharing expertise and ideas is extremely
important so we can make as much progress as possible
during these four years. "
Additional objectives of the study include
determining the cost-benefits of cultural
practices and economic impacts of ARR.
At left, Ksenija Gasic, Clemson University
breeder and geneticist, examines a peach
tree. Below, evidence of armillaria root rot.
Photos: Clemson University
Georgia peach growers.
" Our main goal is to obtain a deliverable management
protocol to be shared with Georgia peach growers for
production in armillaria infested soils, " Chavez said. " This
could be from using resistance sources such as MP-29 as
a rootstock and/or Root Collar Excavation with Guardian
rootstocks. The idea is to have a plan that can be quickly
deployed by growers. "
Economic impacts and outreach
The economics team, led by Michael Vassalos, a Clemson
associate professor of agribusiness, will design surveys to
help determine economic effects of ARR and impacts that
proposed solutions may have in affected regions.
" ARR can have a devastating impact on the profitability
of peaches, cherries and almonds, " said Tyler Mark, an
agricultural economist with the University of Kentucky who
also is on the economics team. " As ARR spreads through an
orchard, it reduces the yield and, eventually, it gets to the
point the orchard is no longer profitable. If the ARR infection
is bad enough, the field may no longer be an acceptable
location to replant an orchard. "
Results of the study will be shared with the public at field
days, meetings, in scientific and trade journals, as well as from
county agents, Cooperative Extension bulletins and posted on
various websites. Tree-fruit nurseries nationwide will deliver
research results to producers.
Consumers and producers will benefit from this crosscountry
collaboration.
" The industry will see an immediate benefit with the change
in cultural practices and direct utilization of new sources of
resistance in nurseries, " Gasic said. " Consumers will benefit
from sustainable stone fruit and nut production, which will
help increase consumption and improve human health and
physical well-being. "
Cultural practices
Cultural practices can extend long-term orchard
productivity on replant sites. Researchers will implement
Above Ground Root Collar Excavation for peach and cherry
and explore using sectorial chimera rootstock in almond
as strategies to increase tree longevity until ARR-resistant
rootstocks are developed.
Above Ground Root Collar Excavation for peach
production was developed by Clemson plant pathologist
Guido Schnabel. In this practice, a tree is planted and grown
on a berm before soil is removed from around a tree's root
collar, exposing the primary roots and fungus to heat, causing
the fungus to dry and die.
Phillip Brannen, Dario Chavez and Jeff Cook from the
University of Georgia will determine how using cultural
practices, such as Root Collar Excavation, can benefit
Fruits and nuts are key players in U.S. agriculture. Figures
from the USDA-National Agricultural Statistics Service
(USDA-NASS) show 645,500 tons of peaches and 334,000
tons of sweet cherries were produced in the U.S. in 2020.
California is the only place in North America where almonds
are commercially grown. The latest figures for almonds from
the USDA-NASS Pacific Regional Office shows 1,275,000 tons
were produced in California in 2019.
Researchers participating in the study include: Clemson:
Ksenjia Gasic, Gregory Reighard, Guido Schnabel, Chris Saski,
Jeff Adelberg, Nishanth Tharayil, Michael Vassalos and Bulent
Koc; University of Georgia: Phillip Brannen, Dario Chavez
and Jeff Cook; University of California-Davis: Tom Gradziel;
USDA-ARS Davis, California: Kendra Baumgartner and John
Preece; Michigan State University: Ray Hammerschmidt and
Amy Iezzoni; and University of Kentucky: Tyler Mark.
This study is funded by a USDA-NIFA Grant 202051181-32142.
Any opinions, findings, and conclusions or
recommendations expressed in this material are those of the
authors and do not necessarily reflect the view of USDANIFA.
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Winter 2021

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