Drought conditions such as those that occurred in Nebraska in 2012 can impact the development of plant diseases. In general drought slows down or prevents the development of plant diseases caused by pathogens that thrive under moist conditions. However, some diseases are favored by drought. This is because when plants are stressed due to lack of moisture or excessive heat, they become more susceptible to these diseases. This article presents examples of diseases of agronomic crops favored by drought and how to manage them. Data are provided on the effect of dry or wet conditions on the profitability of applying fungicides to control foliar fungal diseases of wheat.
Charcoal Rot Diseases of Field Crops
Aspergillus Ear Rot and Aflatoxin Contamination
Fusarium Diseases
Phoma Black Stem of Sunflower
Root and Crown Diseases of Wheat
Management of Foliar Diseases of Wheat with Fungicides in a Dry versus a Wet Growing Seaso

Giesler, Loren

Harveson, Robert

Jackson-Ziems, Tamra A.

Korus, Kevin

Liu, Bo

Wegulo, Stephen

English

DigitalCommons@University of Nebraska

University of Nebraska - LincolnDigitalCommons@University of Nebraska - LincolnPapers in Plant Pathology Plant Pathology Department2013Impacts of Drought on Disease Development andManagementStephen WeguloUniversity of Nebraska-Lincoln, swegulo2@unl.eduLoren GieslerUniversity of Nebraska-Lincoln, lgiesler1@unl.eduRobert HarvesonUniversity of Nebraska-Lincoln, rharveson2@unl.eduTamra A. Jackson-ZiemsUniversity of Nebraska-Lincoln, tjackson3@unl.eduBo LiuUniversity of Nebraska, West Central Research and Extension CenterSee next page for additional authorsFollow this and additional works at: http://digitalcommons.unl.edu/plantpathpapersPart of the Other Plant Sciences Commons, Plant Biology Commons, and the Plant PathologyCommonsThis Article is brought to you for free and open access by the Plant Pathology Department at DigitalCommons@University of Nebraska - Lincoln. Ithas been accepted for inclusion in Papers in Plant Pathology by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln.Wegulo, Stephen; Giesler, Loren; Harveson, Robert; Jackson-Ziems, Tamra A.; Liu, Bo; and Korus, Kevin, "Impacts of Drought onDisease Development and Management" (2013). Papers in Plant Pathology. 537.http://digitalcommons.unl.edu/plantpathpapers/537AuthorsStephen Wegulo, Loren Giesler, Robert Harveson, Tamra A. Jackson-Ziems, Bo Liu, and Kevin KorusThis article is available at DigitalCommons@University of Nebraska - Lincoln: http://digitalcommons.unl.edu/plantpathpapers/537Impacts of Drought on Disease  Development and Management  Stephen Wegulo, Extension Plant Pathologist Loren Giesler, Extension Plant Pathologist Robert Harveson, Extension Plant Pathologist Tamra Jackson-Ziems, Extension Plant Pathologist Bo Liu, Extension Plant Pathologist Kevin Korus, Extension Educator   Drought conditions such as those that occurred in Nebraska in 2012 can impact the development of plant diseases.  In general drought slows down or prevents the development of plant diseases caused by pathogens that thrive under moist conditions.  However, some diseases are favored by drought.  This is because when plants are stressed due to lack of moisture or excessive heat, they become more susceptible to these diseases.  This article presents examples of diseases of agronomic crops favored by drought and how to manage them.  Data are provided on the effect of dry or wet conditions on the profitability of applying fungicides to control foliar fungal diseases of wheat.  Charcoal Rot Diseases of Field Crops Charcoal rot, also known as dry-weather wilt in soybean, is caused by the fungus Macrophomina phaseolina and can affect corn, sorghum, soybean, sunflowers, and dry beans (for which it is has been named ashy stem blight). The fungus has a widespread distribution and wide host range. Microsclerotia (hardened fungal survival bodies) are formed inside infected crop tissue. These microsclerotia are how the fungus overwinters in infested crop debris and soil. Survival of microsclerotia is several years in dry soil but only a few weeks in wet, saturated soils.  As most rotations include hosts for this fungus every year, the potential for the pathogen to be present in many fields is high and will be favored by dry conditions.  Favorable Environmental Conditions.  Charcoal rot thrives in the hottest, driest part of the growing season. This is why it was more common in the 2012 production season.   Charcoal rot develops when there is a high level of the pathogen in the soil and when plants are under stress from hot dry weather. Infection of soybean typically occurs early in the season at the emergence and early seedling growth stages. These seedling infections remain latent until environmental stresses (drought and high ambient temperatures) occur during the R1 (flowering) -R7 (mature pod) growth stages.  In corn, high soil temperatures (98°F) and low soil moisture during grain fill are known to be related to higher levels of charcoal rot. Symptoms of Charcoal Rot.  Seedling damage has been found in soybean when infected seed is planted, but this has not been observed in Nebraska. Typically, symptoms occur after midseason during the reproductive stages of crop development. Infected plants produce slightly smaller leaflets than healthy plants and have reduced vigor. As the disease advances, leaflets yellow, then wilt and turn brown. The brown leaves remain attached to the petioles (leaf stems). A light gray of silver discoloration will be visible in the taproot and lower stem when plants are split open. Black specs (microsclerotia) will be visible in this tissue of the stem and tap root. Outer tissues will have black, dusty microsclerotia. Plants in the driest parts of the field will typically show symptoms first. Upper pods may have poor fill and general low plant vigor. In some cases, the upper one-third of the plant may have only flat pods without seed.    In corn and sorghum, internal shredding of the lower nodes will occur with dark black sclerotia being very visible when the stalks are split.  Like the name of this disease, the plant will look like charcoal inside the stem and the microslerotia will be attached to the vascular tissue strands in the stalk. Management of Charcoal Rot •  Seed treatments have not been demonstrated to be effective even though early season infections are common and symptoms develop at grain fill. • Reducing plant density will reduce drought stress and reduce charcoal rot. • Tillage does not affect this disease, as the microsclerotia will survive several years. • Use of resistant varieties and hybrids. • Crop rotation to non-hosts such as wheat can help reduce microsclerotia numbers.   Aspergillus Ear Rot and Aflatoxin Contamination   Aspergillus ear rot of corn is another important disease in drought-damaged and non-irrigated fields.  This disease receives attention because the fungal species that cause it (usually Aspergillus flavus and A. parasiticus), can 2013 Proceedings : Crop Production Clinics  125also produce aflatoxin, which can be toxic to animal and human consumers of contaminated grain.  You can find more details on this disease and the mycotoxin, as well as how to manage stored grain to minimize contamination in grain in other articles in the CPC Proceedings: • Corn Disease Update  • Grain Storage To Minimize Mold And Mycotoxins   Fusarium Diseases Fusarium pathogens are microbes which exist in soil and on crop residues for a long time. Many factors can lead to diseases caused by Fusarium. Plant stress, such as drought, is one of the factors that increase the incidence and severity of these diseases.  Fusarium species have been associated with many important diseases of corn, wheat and soybean, causing significant yield losses.  Drought can significantly impact these diseases. Fusarium stalk rot, ear rot, and kernel rot of corn caused by Fusarium verticillioides can cause significant yield losses and mycotoxin contamination under drought conditions. Wheat root diseases, such as common root rot caused by Bipolaris sorokiniana, and Fusarium crown rot caused by Fusarium spp., are also more severe under drought conditions.  Early root infections by these pathogens can cause severe yield reduction in dry soils. However, drought will reduce the potential for sudden death syndrome (SDS) in soybean but can favor other Fusarium infections causing Fusarium wilt.    Management of Fusarium Diseases  • Minimize stress and injury by herbicides, foliar diseases, hail damage or drought • Optimize the soil fertility level • Minimize soil compaction • Use fungicide-treated seed • Crop rotation with non-host crops can reduce pathogen inoculum • Plant resistant/tolerant cultivars  Additional information on Fusarium diseases can be found in the NebGuide “Major Fusarium Diseases on Corn, Wheat and Soybeans in Nebraska”. Phoma Black Stem of Sunflower  Phoma black stem is a stalk rot disease caused by the fungal pathogen Phoma macdonaldii.  It is characterized by large, black shiny lesions that may reach several inches in length.  Infection generally starts on leaves from airborne or rain-splashed conidia.  The pathogen makes its way down the petiole to the point of attachment on the stem before causing the black lesions on stems. Although moist weather shortly before and after flowering is beneficial to the pathogen, periods of stress prior to this such as drought, predisposes the plants, making the potential damage from the infection greater.  The pathogen may also girdle the stems at the soil line, causing premature maturation, reduction in head size and poor seed fill in heads.  Stem infections also become more prone to lodging. The pathogen is residue-borne, so rotation and some type of tillage will help reduce inoculum in the soil.  Insect control can also limit spread since their feeding can also provide openings for the pathogen to initially infect plants.  Root and Crown Rot Diseases of Wheat  Root and crown rot diseases in wheat are often overlooked because of the absence of obvious above-ground symptoms.  These diseases are caused by several different fungi.  The diseases caused by fungi in the genera Bipolaris and Fusarium are favored by dry soil conditions.  Therefore, there is an increased risk for the occurrence of these diseases in the 2012 fall-sown winter wheat crop due to the drought of 2012.  When seedlings are attacked by these fungi, winter survival is reduced due to seedling blights.  Later in the growing season, root and crown rots develop.  The fungus Bipolaris sorokiniana causes common root rot.  The disease is characterized dark-brown to black necrotic lesions on roots, subcrown internodes, and stem bases.  Discoloration of the subcrown internode is diagnostic of the disease.  Several Fusarium species cause Fusarium foot rot and dryland foot rot.  The most common symptom of Fusarium foot rot is a dark-brown lesion around the node of mature plants.  Long and thin dark-brown vertical streaks are also commonly seen on the lower stem.  In dryer areas, dryland foot rot may develop.  It is characterized by a dark-brown lesion that girdles the entire stem base.  Affected tissue becomes soft and white, and a pink fungal growth bearing orange spore masses may develop.    Management of Root and Crown Rot Diseases of Wheat  • When possible, irrigate fields to reduce stress due to inadequate moisture. • Avoid excessive nitrogen fertilization.  Under dry conditions, excessive nitrogen promotes vegetative growth (especially tiller formation) to levels that cannot be sustained through heading and grain-fill.  The excessive growth prematurely depletes available soil water.  This increases water stress which predisposes plants to severe root and crown rot diseases. • Severely affected fields in the current cropping cycle (2012-2013) should be rotated to a non-cereal crop in future cropping cycles to reduce fungal inoculum for root and crown rot diseases. • Damage from these diseases can further be reduced by planting pathogen-free, fungicide-treated seed. • Planting drought-tolerant varieties can also help to reduce loss due to root and crown rot diseases.  Management of Foliar Diseases of Wheat with Fungicides in a Dry versus a Wet Growing Season 126  2013 Proceedings : Crop Production Clinics Foliar fungal diseases of wheat are favored by moisture.  They include the rusts (leaf, stripe, and stem rust) and the leaf spots such as tan spot, spot blotch, and Septoria leaf blotch.  Field experiments were conducted in Nebraska in 2006 (dry year) and 2007 (wet year) to demonstrate the effects of applying foliar fungicides on disease severity, yield, yield increase, and economic returns under these two environmental conditions.  In both years, the experiments were conducted at Mead, Clay Center, North Platte, and Sidney.  The fungicides applied were Quilt, Headline, Tilt, Quadris, and Stratego.  They were applied to winter wheat cv. Millennium at the stem elongation or the flag leaf growth stage.  Table I shows average total rainfall in the months of May, June, and July and averages of disease severity, yield, yield increase, and net return across fungicides and locations in each year.  The data show that net returns from fungicide application to control foliar fungal diseases of wheat were almost negligible in the dry year, but were substantial in the wet year.  Therefore, when foliar fungal disease development is limited due to dry conditions during the wheat growing season, fungicide application may not be profitable and may actually result in a net loss.       Table I.  Summary data from experiments conducted to determine the effects of fungicides on foliar fungal disease severity, yield, yield increase, and net return in winter wheat cv. Millennium in Nebraska in 2006 and 2007.  2006 (dry) 2007 (wet) Avg total rain (in): May-July 6 12 Avg temp (oF): May-July 70 69 Avg disease severity (%)             Sprayed plots 2 22           Unsprayed plots 4 59 Avg yield (bu/A)             Sprayed plots 44 69           Unsprayed plots 38 49 Avg yield increase (bu/A) 6 20 Average net return ($/A)a 5 76 Probability of a profit 0.63 1.00  aNet return was calculated based on a wheat price of $3.87/A in 2006 and $4.83/A in 2007. 2013 Proceedings : Crop Production Clinics  127

Impacts of Drought on Disease Development and Management

UNL | Libraries

University of Nebraska - Lincoln
DigitalCommons@University of Nebraska - Lincoln
Papers in Plant Pathology Plant Pathology Department
2013
Impacts of Drought on Disease Development and
Management
Stephen Wegulo
University of Nebraska-Lincoln, swegulo2@unl.edu
Loren Giesler
University of Nebraska-Lincoln, lgiesler1@unl.edu
Robert Harveson
University of Nebraska-Lincoln, rharveson2@unl.edu
Tamra A. Jackson-Ziems
University of Nebraska-Lincoln, tjackson3@unl.edu
Bo Liu
University of Nebraska, West Central Research and Extension Center
See next page for additional authors
Follow this and additional works at: http://digitalcommons.unl.edu/plantpathpapers
Part of the Other Plant Sciences Commons, Plant Biology Commons, and the Plant Pathology
Commons
This Article is brought to you for free and open access by the Plant Pathology Department at DigitalCommons@University of Nebraska - Lincoln. It
has been accepted for inclusion in Papers in Plant Pathology by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln.
Wegulo, Stephen; Giesler, Loren; Harveson, Robert; Jackson-Ziems, Tamra A.; Liu, Bo; and Korus, Kevin, "Impacts of Drought on
Disease Development and Management" (2013). Papers in Plant Pathology. 537.
http://digitalcommons.unl.edu/plantpathpapers/537
Authors
Stephen Wegulo, Loren Giesler, Robert Harveson, Tamra A. Jackson-Ziems, Bo Liu, and Kevin Korus
This article is available at DigitalCommons@University of Nebraska - Lincoln: http://digitalcommons.unl.edu/plantpathpapers/537
Impacts of Drought on Disease  
Development and Management 
 
Stephen Wegulo, Extension Plant Pathologist 
Loren Giesler, Extension Plant Pathologist 
Robert Harveson, Extension Plant Pathologist 
Tamra Jackson-Ziems, Extension Plant Pathologist 
Bo Liu, Extension Plant Pathologist 
Kevin Korus, Extension Educator 
 
 
Drought conditions such as those that occurred in 
Nebraska in 2012 can impact the development of plant 
diseases.  In general drought slows down or prevents the 
development of plant diseases caused by pathogens that 
thrive under moist conditions.  However, some diseases 
are favored by drought.  This is because when plants are 
stressed due to lack of moisture or excessive heat, they 
become more susceptible to these diseases.  This article 
presents examples of diseases of agronomic crops favored 
by drought and how to manage them.  Data are provided 
on the effect of dry or wet conditions on the profitability of 
applying fungicides to control foliar fungal diseases of 
wheat. 
 
Charcoal Rot Diseases of Field Crops 
Charcoal rot, also known as dry-weather wilt in 
soybean, is caused by the fungus Macrophomina 
phaseolina and can affect corn, sorghum, soybean, 
sunflowers, and dry beans (for which it is has been named 
ashy stem blight). The fungus has a widespread 
distribution and wide host range. Microsclerotia (hardened 
fungal survival bodies) are formed inside infected crop 
tissue. These microsclerotia are how the fungus 
overwinters in infested crop debris and soil. Survival of 
microsclerotia is several years in dry soil but only a few 
weeks in wet, saturated soils.  As most rotations include 
hosts for this fungus every year, the potential for the 
pathogen to be present in many fields is high and will be 
favored by dry conditions.  
Favorable Environmental Conditions.  Charcoal rot 
thrives in the hottest, driest part of the growing season. 
This is why it was more common in the 2012 production 
season.   Charcoal rot develops when there is a high level 
of the pathogen in the soil and when plants are under stress 
from hot dry weather. Infection of soybean typically 
occurs early in the season at the emergence and early 
seedling growth stages. These seedling infections remain 
latent until environmental stresses (drought and high 
ambient temperatures) occur during the R1 (flowering) -R7 
(mature pod) growth stages.  In corn, high soil 
temperatures (98°F) and low soil moisture during grain fill 
are known to be related to higher levels of charcoal rot. 
Symptoms of Charcoal Rot.  Seedling damage has 
been found in soybean when infected seed is planted, but 
this has not been observed in Nebraska. Typically, 
symptoms occur after midseason during the reproductive 
stages of crop development. Infected plants produce 
slightly smaller leaflets than healthy plants and have 
reduced vigor. As the disease advances, leaflets yellow, 
then wilt and turn brown. The brown leaves remain 
attached to the petioles (leaf stems). A light gray of silver 
discoloration will be visible in the taproot and lower stem 
when plants are split open. Black specs (microsclerotia) 
will be visible in this tissue of the stem and tap root. Outer 
tissues will have black, dusty microsclerotia. Plants in the 
driest parts of the field will typically show symptoms first. 
Upper pods may have poor fill and general low plant vigor. 
In some cases, the upper one-third of the plant may have 
only flat pods without seed.    
In corn and sorghum, internal shredding of the lower 
nodes will occur with dark black sclerotia being very 
visible when the stalks are split.  Like the name of this 
disease, the plant will look like charcoal inside the stem 
and the microslerotia will be attached to the vascular tissue 
strands in the stalk. 
Management of Charcoal Rot 
•  Seed treatments have not been demonstrated to 
be effective even though early season infections 
are common and symptoms develop at grain fill. 
• Reducing plant density will reduce drought stress 
and reduce charcoal rot. 
• Tillage does not affect this disease, as the 
microsclerotia will survive several years. 
• Use of resistant varieties and hybrids. 
• Crop rotation to non-hosts such as wheat can help 
reduce microsclerotia numbers. 
 
 
Aspergillus Ear Rot and Aflatoxin Contamination 
 
 Aspergillus ear rot of corn is another important 
disease in drought-damaged and non-irrigated fields.  This 
disease receives attention because the fungal species that 
cause it (usually Aspergillus flavus and A. parasiticus), can 
2013 Proceedings : Crop Production Clinics  125
also produce aflatoxin, which can be toxic to animal and 
human consumers of contaminated grain.  You can find 
more details on this disease and the mycotoxin, as well as 
how to manage stored grain to minimize contamination in 
grain in other articles in the CPC Proceedings: 
• Corn Disease Update  
• Grain Storage To Minimize Mold And Mycotoxins  
 
Fusarium Diseases 
Fusarium pathogens are microbes which exist in soil 
and on crop residues for a long time. Many factors can 
lead to diseases caused by Fusarium. Plant stress, such as 
drought, is one of the factors that increase the incidence 
and severity of these diseases.  Fusarium species have 
been associated with many important diseases of corn, 
wheat and soybean, causing significant yield losses.  
Drought can significantly impact these diseases. Fusarium 
stalk rot, ear rot, and kernel rot of corn caused by 
Fusarium verticillioides can cause significant yield losses 
and mycotoxin contamination under drought conditions. 
Wheat root diseases, such as common root rot caused by 
Bipolaris sorokiniana, and Fusarium crown rot caused by 
Fusarium spp., are also more severe under drought 
conditions.  Early root infections by these pathogens can 
cause severe yield reduction in dry soils. However, 
drought will reduce the potential for sudden death 
syndrome (SDS) in soybean but can favor other Fusarium 
infections causing Fusarium wilt. 
   
Management of Fusarium Diseases 
 
• Minimize stress and injury by herbicides, foliar 
diseases, hail damage or drought 
• Optimize the soil fertility level 
• Minimize soil compaction 
• Use fungicide-treated seed 
• Crop rotation with non-host crops can reduce 
pathogen inoculum 
• Plant resistant/tolerant cultivars 
 
Additional information on Fusarium diseases can be found 
in the NebGuide “Major Fusarium Diseases on Corn, 
Wheat and Soybeans in Nebraska”. 
Phoma Black Stem of Sunflower 
 
Phoma black stem is a stalk rot disease caused by the 
fungal pathogen Phoma macdonaldii.  It is characterized 
by large, black shiny lesions that may reach several inches 
in length.  Infection generally starts on leaves from 
airborne or rain-splashed conidia.  The pathogen makes its 
way down the petiole to the point of attachment on the 
stem before causing the black lesions on stems. 
Although moist weather shortly before and after 
flowering is beneficial to the pathogen, periods of stress 
prior to this such as drought, predisposes the plants, 
making the potential damage from the infection greater.  
The pathogen may also girdle the stems at the soil line, 
causing premature maturation, reduction in head size and 
poor seed fill in heads.  Stem infections also become more 
prone to lodging. 
The pathogen is residue-borne, so rotation and some 
type of tillage will help reduce inoculum in the soil.  Insect 
control can also limit spread since their feeding can also 
provide openings for the pathogen to initially infect plants. 
 
Root and Crown Rot Diseases of Wheat 
 
Root and crown rot diseases in wheat are often 
overlooked because of the absence of obvious above-
ground symptoms.  These diseases are caused by several 
different fungi.  The diseases caused by fungi in the genera 
Bipolaris and Fusarium are favored by dry soil conditions.  
Therefore, there is an increased risk for the occurrence of 
these diseases in the 2012 fall-sown winter wheat crop due 
to the drought of 2012.  When seedlings are attacked by 
these fungi, winter survival is reduced due to seedling 
blights.  Later in the growing season, root and crown rots 
develop.  The fungus Bipolaris sorokiniana causes 
common root rot.  The disease is characterized dark-brown 
to black necrotic lesions on roots, subcrown internodes, 
and stem bases.  Discoloration of the subcrown internode 
is diagnostic of the disease.  Several Fusarium species 
cause Fusarium foot rot and dryland foot rot.  The most 
common symptom of Fusarium foot rot is a dark-brown 
lesion around the node of mature plants.  Long and thin 
dark-brown vertical streaks are also commonly seen on the 
lower stem.  In dryer areas, dryland foot rot may develop.  
It is characterized by a dark-brown lesion that girdles the 
entire stem base.  Affected tissue becomes soft and white, 
and a pink fungal growth bearing orange spore masses may 
develop.   
 
Management of Root and Crown Rot Diseases of Wheat 
 
• When possible, irrigate fields to reduce stress due 
to inadequate moisture. 
• Avoid excessive nitrogen fertilization.  Under dry 
conditions, excessive nitrogen promotes 
vegetative growth (especially tiller formation) to 
levels that cannot be sustained through heading 
and grain-fill.  The excessive growth prematurely 
depletes available soil water.  This increases 
water stress which predisposes plants to severe 
root and crown rot diseases. 
• Severely affected fields in the current cropping 
cycle (2012-2013) should be rotated to a non-
cereal crop in future cropping cycles to reduce 
fungal inoculum for root and crown rot diseases. 
• Damage from these diseases can further be 
reduced by planting pathogen-free, fungicide-
treated seed. 
• Planting drought-tolerant varieties can also help 
to reduce loss due to root and crown rot diseases. 
 
Management of Foliar Diseases of Wheat with 
Fungicides in a Dry versus a Wet Growing Season 
126  2013 Proceedings : Crop Production Clinics
 
Foliar fungal diseases of wheat are favored by 
moisture.  They include the rusts (leaf, stripe, and stem 
rust) and the leaf spots such as tan spot, spot blotch, and 
Septoria leaf blotch.  Field experiments were conducted in 
Nebraska in 2006 (dry year) and 2007 (wet year) to 
demonstrate the effects of applying foliar fungicides on 
disease severity, yield, yield increase, and economic 
returns under these two environmental conditions.  In both 
years, the experiments were conducted at Mead, Clay 
Center, North Platte, and Sidney.  The fungicides applied 
were Quilt, Headline, Tilt, Quadris, and Stratego.  They 
were applied to winter wheat cv. Millennium at the stem 
elongation or the flag leaf growth stage.  Table I shows 
average total rainfall in the months of May, June, and July 
and averages of disease severity, yield, yield increase, and 
net return across fungicides and locations in each year.  
The data show that net returns from fungicide 
application to control foliar fungal diseases of wheat were 
almost negligible in the dry year, but were substantial in 
the wet year.  Therefore, when foliar fungal disease 
development is limited due to dry conditions during the 
wheat growing season, fungicide application may not be 
profitable and may actually result in a net loss. 
 
 
 
 
 
 
Table I.  Summary data from experiments conducted to determine the effects of fungicides on foliar fungal disease 
severity, yield, yield increase, and net return in winter wheat cv. Millennium in Nebraska in 2006 and 2007. 
 2006 (dry) 2007 (wet) 
Avg total rain (in): May-July 6 12 
Avg temp (oF): May-July 70 69 
Avg disease severity (%)   
          Sprayed plots 2 22 
          Unsprayed plots 4 59 
Avg yield (bu/A)   
          Sprayed plots 44 69 
          Unsprayed plots 38 49 
Avg yield increase (bu/A) 6 20 
Average net return ($/A)a 5 76 
Probability of a profit 0.63 1.00 
 
aNet return was calculated based on a wheat price of $3.87/A in 2006 and $4.83/A in 2007.
 
2013 Proceedings : Crop Production Clinics  127


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Impacts of Drought on Disease Development and Management

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