Elevating Grain Storage
Entomologists Paul Flinn (left)
and David Hagstrum discuss
sampling methods to use in
the areawide intergrated pest
management (IPM) program for
|Word-of-mouth advertising is
important to spreading good news and good practices among people.
ARS entomologist David W. Hagstrum hopes
that in a few years grain elevator operators will pass on information being
gathered now that could save the wheat industry millions of dollars.
Stored-grain insects account for multimillion-dollar losses annually in this
Each year, 2 billion bushels of wheat are produced in the United States, with
most of it being stored at one time or another in an elevator. Some is stored
before milling, but much of it is awaiting export to other countries. In either
case, damage to stored grain by the lesser grain borer, rice weevil, red flour
beetle, and rusty grain beetle costs the U.S. wheat industry about $500 million
"Pest management is important for all types of grain elevators because
insects move along with grain as it makes its way through the marketing system.
Failure to control pests at just a few elevators can provide sources of insect
infestation that can lower the quality of much larger quantities of grain as
it's commingled in the marketing system," says Hagstrum.
The lesser grain borer develops and
feeds inside wheat kernels.
| Hagstrum is based at ARS' Grain
Marketing and Production Research Center (GMPRC) in Manhattan, Kansas. Since
July of 1998, he and other Kansas and Oklahoma scientists have been monitoring
insect levels and current pest management practices at 13 elevators in Kansas
and 15 in Oklahoma.
In the first year of this 5-year study, the scientists gathered baseline data,
taking more than 20,000 grain samples from the 30 million bushels of wheat
stored at these elevators.
Insect-damaged kernels are caused
by internal-feeding grain insects.
If more than 32 damaged kernels
are found per 100 grams of wheat,
the value of the grain is greatly decreased.
| "This effort is unique. These
aren't laboratory studies; instead, they focus on day-to-day management
practices of grain elevatorshow these practices affect the cost and
effectiveness of insect control and how, in turn, the economics of moving and
storing grain are affected," says Hagstrum.
Integrated Pest Management
A collaborative effort between major grain-handling companies, Kansas State
University, Oklahoma State University, and ARS, this study is the largest of
its kind. Federal and state researchers are working with elevator managers
through industry cooperators who own the networks of grain elevators. The
purpose of the project is to evaluate procedures that might be useful in an
integrated pest management (IPM) system for wheat storage.
Sampling is a key tool for determining the level of insect infestation in the
stored wheat. To estimate changes in insect populations, research technicians
sampled grain from elevators in Kansas and Oklahoma and from trucks that
deliver it to terminals. The researchers took three 1-gallon samples from every
1,000 bushels of wheat sampled5 to 50 times larger than the commonly used
sampling rate. They found that most of the wheat trucked to the elevators is
relatively free of insects.
Biological technician Ken
Friesen uses an inclined sieve
to separate insects from a
large wheat sample. The insects
are identified and counted
to estimate infestation in stored
"Insects are detected with probe traps within a month after the grain
enters the elevators," says R.F. (Skip) Allen, who manages the project in
Hutchinson, Kansas. In Watonga, Oklahoma, Allen's counterpart is Stan Miller.
Hagstrum and his team identified three main ways to improve integrated pest
management: (1) cooling the grain earlier in the season, particularly right
after it enters the bin; (2) cleaning empty bins more thoroughly; and (3)
fumigating wheat only when insect infestations reach unacceptable levels. All
three practices create an environment in which beneficial insect parasites can
thrive and attack the stored-grain insect larvae.
"These aren't necessarily new ideas," says Hagstrum, "but now we
have substantial data to show they are cost-effective." Cooling newly
harvested grain right after it enters the bin, rather than waiting until fall
when elevators typically use fans to aerate (cool) the grain, can reduce insect
problems and the cost of pest management. The cost of early cooling is less
than fumigation, currently estimated at 1.57 cents per bushel for storage in
steel bins and 2.35 cents per bushel for storage in concrete bins.
Most grain elevators have thin wire cables to check the temperature of the
grain inside. These cables run through the center of the bin from top to
bottom. Sensors are positioned every 6 feet along the cable for measuring
"A conscientious elevator manager records the temperatures, keeping watch
for any rise in temperature that might indicate the presence of insects,"
Data loggerssmall recording devices attached to the aeration
fansare being used by the IPM researchers. "With these, we can show
the workers how long the fans had been runningin some cases many hours
after the grain had already cooled. Being able to automatically cut back on fan
operating time helps save on energy costs," says Hagstrum.
These data will be welcome news for the grain-storage industry. One-third of
the storage bins included in the project have aeration fans to cool the grain,
but controlling devices are needed to shut the fans off when the outside air
temperature is insufficient to cool the grain, according to Hagstrum.
"There are five or six species of tiny parasitoid wasps that range in size
from 1/8 to 1/4 inch and are normally found living in grain. They are the
good guys because they don't feed on the grain but attack the
larvae of the rusty grain beetle, lesser grain borer, and rice weevil,"
says Paul W. Flinn, an ARS entomologist at GMPRC.
The beneficial insects are another reason for reducing the use of
fumigationbecause it kills the good ones along with the bad. These tiny
wasps don't pose a threat to grain quality because they're completely removed
during ordinary grain cleaning.
Phosphine is the fumigant of choice for controlling beetles that damage stored
grain. But the U.S. Environmental Protection Agency is proposing new
risk-mitigating measures for phosphine.
"If fumigations were more effective and done only when needed, the risk of
using phosphine could be substantially less for grain workers," says
In 1995, Flinn and other GMPRC scientists designed a computer program, Stored
Grain Advisor, for farmers and grain elevator operators to predict when insect
infestations will reach levels requiring chemical pest control. The computer
program is available on the World Wide Web at
As part of the areawide IPM project, the scientists are developing an advanced
version, Stored Grain Advisor Pro, which will be available free to the public
on the GMPRC web site by the end of the project.
The Kansas-Oklahoma areawide project is one of several ARS programs developed
in response to USDA's 1994 Integrated Pest Management Initiative.
Recommendations based on this research are expected to be made in 2002. That's
when word-of-mouth advertising should reach its peak, hopes Hagstrum.
The benefits of areawide IPM are within reach. Fewer workers will be exposed to
fumigants and fewer insects will be able to develop resistance to fumigants.
Ultimately, these measures should strengthen the competitiveness of U.S. wheat
in the export market.By Linda
McGraw, Agricultural Research Service Information Staff.
This research is part of New Uses, Quality, and Marketability of Plant and
Animal Products, an ARS National Program (#306) described on the World Wide Web
David W. Hagstrum and
Paul W. Flinn are in the USDA-ARS
Biological Research Unit, Grain
Marketing and Production Research Center, 1515 College Ave., Manhattan, KS
66502; phone (785) 776-2718 [Hagstrum], (785) 776-2707 [Flinn], fax (785)
"Elevating Grain Storage Practices" was
published in the April 2000 issue
of Agricultural Research magazine.