Charcoal rot is tough to beat - Farm Progress Issue Search Engine

Nebraska Farmer – April 2015
Crop Production
HERE is bad news when it comes to
charcoal rot in Nebraska. You can’t
beat it with a simple crop rotation
because it loves a huge host of plants,
including corn, soybeans, wheat, alfalfa,
sorghum and dry beans, just to name a
few. Seed and foliar fungicide treatments
don’t work to reduce it.
According to Tamara Jackson-Ziems,
Nebraska Extension crop pathologist,
there are no resistance packages available
in modern hybrids. And, in 2014, CR, or
dry weather wilt as it is sometimes known,
was more widespread in soybeans in the
state, with confirmations in Cass, Burt,
Saunders and Keith counties. “Losses can
range from very little loss to up to 50%, depending on the condition,” Jackson-Ziems
says. The good news is that because it is
a dry-weather fungus, it hits mostly nonirrigated fields.
CR was an important disease in 2014
because of high temperatures and dry
conditions in parts of the state. It also
showed up in regions struck by wind and
hail that already had stressed the crops.
CR is caused by Macrophomina phaseolina, a soil and seedborne fungus that
has over 500 hosts. It overwinters in crop
debris and soil, surviving in hardened
fungal structures that resemble charcoal
dust. Food reserves in these structures
allow it to remain dormant until conditions
for growth are favorable. It can actually be
present for many years without causing
identifiable infection.
“We saw many Nebraska soybean
fields with symptoms in 2014,” says Tony
Adesemoye Nebraska Extension disease
management specialist. “The disease may
not occur every time, except when conditions are conducive for the pathogen.”
The United Soybean Board estimates that
in 2011 soybean losses were 30 million
bushels in 13 northern states and over a
quarter-million in Nebraska.
In soybeans, symptoms include
browning or yellowing of leaves and
stem, smaller-than-normal leaflets, blackcolored growths on the lower stem and
root, and silver or gray lesions. It is easy
to detect wilting in the infected portions
of the field. In some cases, pods or ears
may fill improperly, causing yield losses.
Adesemoye’s research studies the biology of soilborne pathogens like CR and
the interactions of those pathogens with
organisms around the root that can be
used as biocontrol agents in controlling
pathogens in an integrated disease management system. “Our program examines
the complex root ecosystems from a systems approach, and uses robust conven-
Reduce plant stress
Managing CR is a matter of reducing
plant stress. Shorter-season varieties
that canopy more quickly will keep soil
temperatures lower during the hottest
part of summer. Measures taken to retain
moisture in the soil through less tillage
or irrigation, as well as proper nutrient
management, help produce healthier
plants. Many pathogens can be controlled
through crop rotation, but CR utilizes so
many different crops as hosts that rotation
will not help, says Jackson-Ziems.
“Early diagnosis of CR does not lead
to immediate rescue treatments in the
growing season,” says Adesemoye.
“Scientific information is emerging on the
pathogen in the state, and the earlier the
information on each infection and sampling in the field, the better the knowledge
on the pathogen. Over time, we will have
better management strategies.”
tional and molecular tools,” Adesemoye
says. “In 2014, we visited field locations
suspected for CR, and we have recovered pathogens, which we are currently
Producers who believe they have CR in
the field should contact the UNL Plant and
Pest Diagnostic Clinic at 402-472-2559, or
call Adesemoye at 308-696-6708.
often night
when you call it a day.
Because it’s
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Charcoal rot is tough to beat