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Head Scab Present in
Darke County’s Wheat
By Justin Petrosino ANR Extension Educator
OSU Extension, Darke County
June 20, 2011
Rainy and moist conditions persisted through wheat anthesis this year.
As a result head scab is once again present in Darke County’s wheat.
However, initial results from a survey conducted by THE Ohio State
University show disease incidence may be lower than last year. With
harvest approaching it is important to be prepared to deal with scab by
knowing some best management practices (BMPs) to deal with scab at
harvest.
As many farmers are aware, head scab is a disease that affects both
grain yield and grain quality of wheat. The disease is caused by the
fungus Fusarium graminearum. The fungus infects wheat during anthesis
if wet conditions, either rain or high humidity, persist. Once the
kernel is infected the disease limits growth causing shriveled kernels.
The disease also produces several toxins, the most widely known is
vomitoxin. The toxin is also referred to as DON which is an
abbreviation for deoxynivelanol. At the time of sale farmers lose money
from the sale price for the reduction in yield and quality. Grain is
tested for vomitoxin so the risk to consumers of wheat products is
non-existent.
On Monday June 13, 2011 Alissa Kriss, a PhD candidate with the
Department of Plant Pathology at OSU, traveled to Darke County and
completed a survey of wheat fields for head scab with the assistance of
Justin Petrosino, OSU Extension Darke County. Initial results from 2011
show that the incidence of head scab ranged from 8 to 15%. Incidence
indicates the number of heads per foot of row with symptoms of the
disease. Although last year only one field in the county was surveyed
incidence was reported around 47%. This was similar to results from
other nearby counties with multiple fields surveyed in 2010. Thankfully
initial results show a lower level of incidence than the bumper crop of
head scab observed last year.
The amount of vomitoxin or DON present in the wheat is still to be
determined. The presence of head scab in wheat indicates that some
amount of vomitoxin will be present. However, conditions during the
maturation of wheat will determine the total amount of toxins present.
Recent research has shown that wet conditions after flowering can
increase the amount of vomitoxin present so the rains over the last few
weeks have not helped the situation. The only way to know the level of
vomitoxin is to test at harvest.
There are several best management practices for dealing with scabby
wheat at harvest. There is no way to treat for head scab or vomitoxin
at this point. Best management practices revolve around limiting the
number of scabby kernels that are harvested and limiting any further
growth. During harvest it is recommended to spend some time adjusting
the combine. Turn up the air to blow out light kernels that are
infected with the disease. If handling scabby wheat be sure to wear
gloves to limit exposure to the toxin. Once harvested make sure to dry
the wheat down to 13.5%. Below this level of moisture, fungal growth
and toxin production will be drastically reduced. Be sure to test grain
for vomitoxin levels, and if the straw is to be baled have it tested.
Scabby wheat blown out the back of the combine will still germinate
this fall. A fall herbicide program should be implemented this year to
control scabby wheat. With the right combination of products it is an
optimal time to control fall emerged marestail, too!
For more information on head scab and current agronomic concerns in
Ohio keep an eye on the CORN Newsletter available at
http://corn.osu.edu/ or visit the Agronomic crops website at
http://agcrops.osu.edu/. There are also factsheets and other
publications available at the OSU Extension, Darke County, office.
Questions and concerns can be directed to Justin Petrosino by calling
(937) 548-5215 or emailing petrosino.3@osu.edu.
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