Validation, Optimization, and Deployment of Fungicide Advisories for Soybean Virginia Soybean Board 2014 Project Report & 2015 Project Proposal Dr. Hillary.
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Validation, Optimization, and Deployment of Fungicide Advisories for Soybean
Virginia Soybean Board
2014 Project Report & 2015 Project Proposal
Dr. Hillary L. Mehl, Plant Pathologist
Dr. David Holshouser, Soybean Agronomist
Tian Zhou, MS Student
Virginia Tech Tidewater AREC
March 12, 2015
Integrated Disease Management - Soybean
• Know your target disease so you can select the best cultivar and fungicide – foliar fungi
• Plant resistant/tolerant cultivars (or be aware of susceptibility to specific diseases)
• Optimize fungicide timing and chemistry for target disease
Do Foliar Fungicides Pay?Points to Consider
• How susceptible or resistant is your cultivar?
• Yield potential – what are you protecting?
• Crop growth stage and timing of fungicide
applications
• Previous crop and cropping system (e.g. no till)
• Disease pressure
• Weather
2014 Objectives
1. Validate and optimize a weather-based disease advisory model for timing of foliar fungicide application in soybean
2. Evaluate profitability of different fungicide spray schedules based on yield response and input costs
3. Initiate development of a web-based disease advisory alert system for soybean
Soybean Weather-Based Fungicide Advisory: Validation Trials 2014
Eastern Virginia AREC (Warsaw)
Tidewater AREC (Suffolk)
R3 FungicideAdvisory Fungicide
No Fungicide
7 on-farm trials2 small plot studies (ARECs)
*
*
*
**
**
* Weather station
Treatments
Fungicide timing vs yield response
R3
Adviso
ry 1
spr
ay*
1 wee
k af
ter R
3
2 wee
ks a
fter R
3
3 wee
ks a
fter R
3
4 wee
ks a
fter R
3
R3 & 2
1 da
ys a
fter R
3
Adviso
ry 2
spr
ays*
Wee
kly s
pray
s be
twee
n R3
and
R5100
110
120
130
5.1 bu/A0.2 bu/A
7.0 bu/A5.3 bu/A2.7 bu/A
11.6 bu/ATAREC EVAREC
Fungicide application timing
% y
ield
re
sp
on
se
c
om
pa
red
to
un
tre
ate
d
Single application
Multiple applications
Each % yield response = 0.6 bu/A
TAREC (Suffolk) – Cercospora blight
*Weather advisory and growth stage-based sprays were made on the same date
EVAREC (Warsaw) – Frogeye leaf spot
County Variety TreatmentSpray Date Fungicide & Rate Yield (bu/A)
Orange Asgrow AG4633 Control NA 47.4 B
R3 July 29 Priaxor - 4 oz/A 52.6 A
Decision Aid Aug 4 Priaxor - 4 oz/A 52.0 A
Culpeper NK S41-J6 Control NA 61.0 A R3 Aug 11 Priaxor – 4 oz/A 59.7 A
Decision Aid Aug 20 Priaxor – 4 oz/A 57.2 AStafford Pioneer P39T67 Control NA 67.8 A R3 Aug 7 Quadris Top - 11 oz/A 69.7 A
Decision Aid Aug 16 Quadris Top - 11 oz/A 70.2 AAmelia Armor 5363 Control NA 41.4 C
R3 Aug 15 Quadris Top – 10 oz/A 47.7 A
Decision Aid Aug 20 Quadris Top – 10 oz/A 46.1 BNottoway Control NA 45.4 B
R3 Sept 16 46.7 A
Decision Aid Sept 26 46.7 ASussex Hubner H53-12R2 Control NA 30.0 B
R3 Sept 3 Stratego YLD – 6 oz/A 34.2 A
Decision AidSept 16 (Sept 9) Stratego YLD – 6 oz/A 32.7 A
Accomack Channel 4206 Control NA 54.7 A
& 4306 R3 Sept 11 Stratego YLD – 4 oz/A 53.6 A
Decision Aid Sept 15 Stratego YLD – 4 oz/A 48.8 A
“Favorable days” vs yield response
4 5 6 7 8 9 10 11 12 13 1490
95
100
105
110
115
120
R² = 0.978270057905727R² = 0.942115792304356
R3
#of days between R3 growth stage and favorable days for disease
Yie
ld (
% o
f u
ntr
eate
d c
on
tro
l)
+1-2 bu/A
+4-6 bu/A
Yield response needed to offset cost of fungicide application in soybean
Treatment cost/A
Soybean price/bu
$9 $10 $11 $12 $13 $14
$15.00 1.7 1.5 1.4 1.3 1.2 1.1
$17.50 1.9 1.8 1.6 1.5 1.3 1.3
$20.00 2.2 2.0 1.8 1.7 1.5 1.4
$22.50 2.5 2.3 2.0 1.9 1.7 1.6
$25.00 2.8 2.5 2.3 2.1 1.9 1.8
$27.50 3.1 2.8 2.5 2.3 2.1 2.0
$30.00 3.3 3.0 2.7 2.5 2.3 2.1
$32.50 3.6 3.3 3.0 2.7 2.5 2.3
$35.00 3.9 3.5 3.2 2.9 2.7 2.5Favorable days for disease development:< 8 days after R3 4-6 bu/A yield response> 8 days after R3 1-2 bu/A yield response (or less)
Virginia Ag Pest and Crop Advisory Blog
http://blogs.ext.vt.edu/ag-pest-advisory/The weather-based advisory needs to be further validated, but preliminary fungicide advisories for soybean will be posted on the Virginia Ag Pest and Crop Advisory Blog in 2015.
Collection of weather data
• Hourly weather data are needed to run model for advisory• Currently using weather stations at a limited number of locations• Considering a weather data service ($100-$200 per site per year)
2014 Conclusions• Fungicide applications are more likely to result in a
significant yield response if favorable conditions for disease development occur within 7 days of the R3 stage.
• Fungicide applications made when weather conditions are favorable for disease development are likely to be profitable.
• Additional years of data including ranges of environmental conditions and detailed assessments of crop and disease development are needed.
2015 Objectives
1. Validate and optimize a weather-based disease advisory for foliar fungicide application in soybean
2. Survey soybean fields for fungicide resistant pathogens
Objective 1: Validate and optimize weather-based disease advisory
• Collect second year of data to validate and optimize weather-based parameters for timing fungicide applications
• Repeat small-plot and on-farm trials comparing growth stage and weather-based fungicide applications
• Collect more detailed information on disease and crop development over time
Objective 2: Survey soybean fields for fungicide resistant pathogens
• Control/management• Resistant cultivars (best)• Rotate out of soybean• Foliar fungicides
• Generally not a problem in VA
• High severity in some fields in 2013 & 2014 (defoliation)
• Potential for up to 30% yield loss in some fields
Frogeye leaf spot (FLS)Causal agent = Cercospora sojina
Virginia - fungicide resistant isolates of FLS confirmed in 2 out of 4 fields sampled in 2014
Strobilurin resistant frogeye leaf spot
Fungicide Resistance
Quinone outside inhibitors (QoIs)/strobilurins are highly effective, broad-spectrum fungicides BUT fungicide resistance can occur rapidly within pathogen populations leading to disease control failures
• Inhibit mitochondrial respiration of fungi by binding to cytochrome bc1 enzyme complex at Qo site (site specific mode of action)
• G193A mutation: Glycine Alanine at codon 143 (complete resistance)
• Single base change in DNA sequence: GGT GCT
Sensitive
Resistant
DNA sequence from cytochrome b gene in Cercospora sojina (frogeye leaf spot fungus)
Strobilurin / QoI fungicides
A DNA-based assay can be used to identify strobilurin resistant FLS
Fungal isolate or infected plant tissue
Extract DNA Amplify DNA by PCR (target sequence conferring sensitivity / resistance to strobilurin fungicides)
Visualize DNA (PCR product) on agarose gel
Resistance mutation
Wild-type (sensitive)
Determine frequency and distribution of strobilurin resistant FLS in Virginia
Why Monitor Resistance?
• Resistance control failures crop losses
• Use of ineffective fungicides may increase resistant strains of fungi
Fungicide trade name
Fungicide common name
Fungicide class* Production rate per acre
Quilt Xcel azoxystrobin + propiconazole
strobilurin + triazole 14.0‑21.0 fl oz
Quadris TOP azoxystrobin + difenoconazole
strobilurin + triazole 8.0‑14.0 fl oz
Stratego YLD trifloxystrobin + prothioconazole
strobilurin + triazole 4.0-4.65 fl oz
Priaxor pyraclostrobin + fluxapyroxad
strobilurin + carboxamide
4.0-8.0 fl oz
Aproach Prima picoxystrobin
cyproconazole
strobilurin + triazole 5.0-6.8 fl oz
Pre-mix fungicides are recommended for fungicide resistance management. However, if strobilurin resistance becomes widespread in Virginia, different fungicide modes of action or rates may need to be recommended.
Fungicides Pre-mixes for Resistance Management
2015 Budget RequestItem Amount requested Graduate student (100%) Salary $ 22,021
Fringe benefits $ 1,486
Wage employee Salary (2 months) $ 4,000
Fringe benefits $ 310
Materials/supplies $ 2,000
TOTAL $ 29,817
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