Pesticide and Environmental Update
Grown Pecans Show Significantly
Higher Yields vs Conventionally Grown!
By Alfredo Flores
Pecan growers might be able to boost their
profits by growing pecans organically, according to Agricultural Research
Service (ARS) scientists studying production systems for this popular tree
U.S. growers provide about 90 percent of
the world's pecans, with an annual crop of about 200 million pounds worth
about $400 million. Pecans, popular in baked goods and confections, are a
good source of protein and contain antioxidants and plant sterols thought
to be beneficial to human health.
In 2002, ARS scientists led by Joe
Bradford, research leader at the agency's Integrated Farming and Natural
Resources Research Unit in Weslaco, Texas, began transitioning a
27-year-old, conventionally managed pecan orchard to a
certified-organic-managed system. The 20-acre test site is located within
the Gebert commercial pecan orchard in Comanche County in north-central
The primary objective of the project is to
provide information to pecan growers on how to convert from conventional
management systems that rely on synthetic chemicals to an organic system.
Contrary to conventional growers'
expectations, the ARS organically treated test site out-yielded the
conventionally managed, chemically fertilized Gebert orchard in each of
the past five years. Yields on ARS' organic test site surpassed the Gebert
commercial orchard by 18 pounds per tree in 2005, and by 12 pounds per
tree in 2007.
The conventional management system
generates about $1,750 per acre when the crop is sold. But the ARS
certified-organic-management system would gross $5,290 per acre.
These greater dollar returns prove that
adopting an organic system and obtaining certification could provide more
income for pecan growers, thanks to increased yields and improved kernel
Organic Pecans: Another Option for
ARS scientists in Weslaco, Texas, are
developing new methods to increase yields and organically manage pecan
The pecan’s name comes from an Algonquian
word meaning “a nut that requires a stone to crack.” Widely consumed
out of hand and used as an ingredient in baked goods and confections,
pecans are a good source of protein. And the antioxidants and plant
sterols they contain may improve consumers’ cholesterol status by
reducing the “bad” LDL cholesterol levels.
Despite only having commercially produced
the nut since the 1880s, U.S. growers now provide roughly 90 percent of
the world’s pecans, with an annual crop of about 200 million pounds
worth about $400 million dollars.
New ARS studies in Weslaco, Texas, are
showing that it may be possible for growers to boost their revenue further
by growing pecans organically.
In 2002, ARS scientists—led by Joe
Bradford, research leader for the Integrated Farming and Natural Resources
Research Unit in Weslaco—began transitioning part of a 27-year-old pecan
orchard from conventional management to certified-organic management. The
20-acre test site is located within the Adolph (Sonny) and Noreen Gebert
pecan orchard in Comanche County, in north-central Texas.
Bradford was contacted by Sonny Gebert in
2001, after Gebert tuned in to a radio show during which the two hosts
mentioned Bradford’s research on organic crops. Gebert then phoned
Bradford, and the two arranged to meet in Goldthwaite, Texas, at a Texas
A&M workshop in 2002. Gebert agreed to let Bradford and his
collaborators manage half of the nearly 800 pecan trees in the Gebert
orchard using organic principles. ARS would manage the older portion of
the orchard, which was planted in 1981. The Geberts would continue to
manage the newer portion, planted in 1986.
The main objective of the project is to
provide pecan growers with information on how to convert to an organic
system from a conventional management system that relies on synthetic
chemicals. Bradford and his technicians are constantly changing the
variables within the system and examining the interactions that result
from those changes.
Healthier Trees From Healthy Soil
The ARS organic management system was based
on first increasing soil organic matter, balancing the nutrients and
biology of the soil, and using organic pesticides only when needed.
Bradford theorized that by improving tree health through improved soil
health, the trees would naturally become more resistant to disease and
insect attack. The researchers decided to evaluate several soil treatments
in the test orchard and to treat the trees aboveground using organic
methods. They began applying treatments in the fall of 2002, shortly after
their first summer visit with Sonny Gebert.
They studied five pecan varieties—Caddo,
Cheyenne, Desirable, Pawnee, and Wichita—applying various organic
amendments several times during the year, both to the soil and to the
leaves. As many as 15 soil fertility and biological treatments were
applied, while the aboveground portion of the orchard received a uniform
foliar treatment. Treatments used include poultry litter and compost, rock
minerals, mycorrhizal fungi, and nutrients such as iron, zinc, boron,
copper, and manganese.
Since the death of Sonny Gebert in early
2008, management of his pecan orchard has been taken over by Danny
Phillips, a retired Extension agent from Hamilton County who is employed
by Noreen Gebert. The ARS scientists continue to travel to the orchard
about once each month from March until the November harvest—the growing
season for pecans—to apply soil treatments and compost teas.
Larry Zibilske, a soil scientist in
Bradford’s research unit, became involved in the project during the 2008
growing season. He is measuring changes in soil microbial properties
resulting from the various treatments applied over the last 6 years. As
soil fertility increases with organic treatments, microbial populations
benefit greatly. Not only do they become more diverse, they also take a
more active role in providing nutrients to the trees and protecting the
roots from pathogens. The key is to modify the soil microbial habitat so
that the beneficial organisms persist and provide a lasting, nurturing
environment for the trees.
Evaluating the Results
Contrary to conventional growers’
expectations, the ARS organically treated test site outyielded the Geberts’
conventionally managed, chemically fertilized orchard in each of 5 years.
The best ARS treatment surpassed the Gebert control by 18 pounds per tree—44.10
pounds compared to 25.85 pounds—in 2005 and by 12 pounds per tree—45.09
pounds compared to 33.39 pounds—in 2007. Because pecans are an
alternate-bearing tree, both orchards’ yields were very low in 2004 and
Compost tea is sprayed on the organic trees
once every 6 weeks throughout the growing season. Compost tea improves
plant health and helps to control insects and diseases.
“This is the most successful organic
project I have been involved with,” says Bradford. “The results are
especially satisfying, because we have shown that it’s possible to grow
nuts under the organic system that are far superior in looks and in taste.”
Also involved in the project are plant
physiologist Nasir Malik and entomologist Allan Showler, who both work in
Bradford’s unit. Malik and Showler will next compare some of the
nutritional values of the organic and conventional pecans harvested this
But What About Pecan Pests?
Another positive result was that the ARS
researchers learned how—with the help of beneficial Trichogramma wasps—to
control the pecan casebearer. As one of pecans’ major pests, the larvae
of this one-third-inch-long gray moth tunnel into the small, immature
nutlets, killing them. The very tiny parasitic wasps of the genus
Trichogramma lay their eggs inside casebearer eggs, turning them black and
preventing the casebearer larvae within from developing.
As a backup control, the scientists used
the organic bacterial insecticide known as “spinosad,” which is
derived naturally from a soil-dwelling bacterium, Saccharopolyspora
The researchers also found that foliar applications
of compost tea—a brew made of compost, small amounts of food sources for
microbes, and water—somewhat increased trees’ resistance to insects
and achieved some disease control when applied each month after flowering.
They think that another major pest of pecans, the pecan weevil, was
somewhat controlled by compost tea applied to soil. Additional research in
2008 will verify whether this treatment will be added to the
recommendations by Bradford and his team.
Currently, ARS scientists are working to
better control pecan scab caused by a fungus that, if not curbed, can
cause entire crops from most varieties to be lost during periods of
frequent rains or extended dew. Scab is the most destructive disease of
pecans in the hot, humid South.
The researchers also believe that the
alternate-bearing characteristic of pecan production will lessen—or
disappear—after several years of organic management. ARS data shows that
pecan trees in the Hamilton organic orchard bear 40 pounds per tree in the
good years and about 4 pounds per tree in the lower yielding years—a
drastic difference that can make or break some of the smaller pecan
producers. Bradford thinks that the organic system will eventually even
out the wild discrepancies between the good and bad yields.
“This year, which is the low-yield year
in the alternate-bearing cycle, the conventional orchard has few to no
pecans, yet our organic orchard has a lot of pecans. The typical 4 pounds
per tree measured in 2004 and 2006 could be at least 15-20 pounds this
year,” he says.
Pecans from the Gebert orchard generally
sell for about $2.00 per pound wholesale. Using the average yield for the
conventional management system of 25 pounds per tree and roughly 35 trees
per acre, sale of the crop generates about $1,750 per acre (25x35x$2). But
the ARS best-management organic system yield of 44 pounds per tree would
gross $3,080 per acre (44x35x$2), for an increase in sales of $1,330 per
acre. While production costs add about $100 per acre, the value of the
pecans is increased by at least $1.50 per pound. Thus, pecans harvested
from an orchard certified as organic would generate $5,290 per acre
[(44x35x$3.50) – $100]—for an increase of $3,540 per acre above the
returns from the conventional management system.
These greater dollar returns prove that
adopting an organic system and obtaining certification could provide a
valuable additional source of income to pecan growers, thanks to increased
yields and improved kernel quality.
“I believe our greatest accomplishment is
that we, as scientists, have shown it’s possible to design a management
system that growers will adopt,” says Bradford. “That’s really the
biggest thing—to prove that this is a change for the better.”
He also notes that converting pecan
production from conventional to organic can translate to other crops. “We
think that the techniques we’ve tested here can apply to peaches,
apricots, apples, walnuts—to all tree crops, and to plants in general.”—By
Alfredo Flores, Agricultural Research Service Information Staff.