Managing Sclerotinia in soybeans with fungicides Michael Wunsch, PhD

Managing Sclerotinia in soybeans
with fungicides
Michael Wunsch, PhD
North Dakota State University - Carrington Research Extension Center
1. Fungicide efficacy & timing:
SOYBEANS vs. CANOLA
Registered fungicides – canola vs. soybeans
FUNGICIDES REGISTERED
FOR CONTROLLING SCLEROTINIA ON CANOLA
BUT NOT SOYBEANS:
Astound (cyprodinil + fludioxonil)
Lance (boscalid)
Proline (prothioconazole) **
Rovral Flo (iprodione)
Quadris (azoxystrobin)**
Quash (metconazole)
Vertisan (penthiopyrad)**
** registered for control or suppression of other soybean diseases
Registered fungicides – canola vs. soybeans
FUNGICIDES REGISTERED
FOR CONTROLLING OR SUPRESSING SCLEROTINIA
ON CANOLA AND SOYBEANS:
Canola
Soybeans
Acapela (picoxystrobin)
0.323 L/ac
0.352 L/ac
Priaxor (fluxapyroxad + pyraclostrobin) 0.182 L/ac
0.182 L/ac
FUNGICIDES REGISTERED
FOR CONTROLLING OR SUPRESSING SCLEROTINIA
ON SOYBEANS BUT NOT CANOLA:
Allegro (fluazinam)
Stratego Pro (prothioconzole + trifoxystrobin)
Fungicide efficacy – importance of fungicide coverage
Application rates:
Lance:
145 – 164 ml/ac
Proline:
148 – 159 ml/ac
Non-treated
Lance
Proline
Non-treated
Lance
Proline
Fungicide efficacy – importance of fungicide coverage
Application rates:
Lance:
170 – 227 ml/ac
Proline:
169 ml/ac
Non-treated
Lance
Proline
Non-treated
Lance
Proline
Fungicide efficacy – canola
Carrington, ND (2015)
Application rates registered
on Canola in Canada:
Acapela: 323 ml/ac
Priaxor: 182 ml/ac
Lance: 142 g/ac
Proline: 127-149 ml/ac
Nozzles: 8001 flat-fan
Pressure: 35 psi
Water volume: 15 gal/ac
Application timing: 10-20% bloom
Sclerotinia
severity
index (%)
Yield
(lbs/ac)
Fungicide efficacy – soybeans (prothioconazole)
CANADA: Prothioconazole is registered in the premix fungicide ‘STRATEGO PRO’
** The quantity of prothioconazole in labeled rate of 231 ml/ac Stratego Pro
equals the quantity of prothioconazole in 84 ml/ac Proline.
Fungicide efficacy – soybeans (picoxystrobin)
CANADA: Picoxystrobin is registered in the fungicide ‘ACAPELA’
Labeled rate of Acapela is 356 ml/ac
Fungicide efficacy – soybeans (picoxystrobin)
CANADA: Picoxystrobin is registered in the fungicide ‘ACAPELA’
Labeled rate of Acapela is 356 ml/ac
Fungicide efficacy – soybeans
(pyraclostrobin + fluxapyroxad)
CANADA: Pyraclostrobin + fluxapyroxad are registered in the fungicide ‘PRIAXOR’
Labeled rate of Priaxor is 182 ml/ac
Fungicide efficacy – soybeans (fluazinam)
CANADA: Fluazinam is registered in the fungicide ‘ALLEGRO’
Labeled rate of Allegro is 356 to 473 ml/ac
Fungicide timing – soybeans
For fungicides registered for control or suppression of
Sclerotinia on soybeans in Canada Stratego Pro
Acapela
Priaxor
Omega
Making applications at R1 is likely optimal with
standard fungicide application practices.
Excellent fungicide coverage appears to be
very important for these chemistries.
Fungicide timing – soybeans
… but applications at R1 are not ideal for all chemistries.
Lance (registered for use on soybeans in the United States but
not in Canada) does not appear to require excellent coverage
for good activity on soybeans.
• Sclerotinia control and soybean yields are maximized when
Lance is applied at early to full R2.
Fungicide timing – soybeans (boscalid)
Narrow row spacing - applications at early to full R2 optimal (80 to 100% R2).
** Boscalid is registered for use on soybeans in the United States but not in Canada.
Fungicide timing – soybeans (boscalid)
Wide row spacing - Applications at full R2 optimal (100% R2).
** Boscalid is registered for use on soybeans in the United States but not in Canada.
2. Economics of using fungicides to
manage Sclerotinia in soybeans
Economics of using fungicides to manage Sclerotinia in soybeans:
Disease control, optimally timed fungicide applications
1. FUNGICIDES REGISTERED FOR CONTROL OR SUPPRESSION
OF SCLEROTINIA IN CANADA:
Prothioconazole (registered as Stratego Pro, a premix with trifloxystrobin)
Picoxystrobin (Acapela)
Pyraclostrobin + fluxapyroxad (Priaxor)
Fluazinam (Allegro)
• Average reduction of Sclerotinia with R1 applications: 44%
• Caution: data set is not very deep; also, chemistries likely differ in
comparative efficacy
2. LANCE:
Not registered in Canada, but the competitive standard in the United States.
• Average reduction of Sclerotinia with R2 applications: 45%
Economics of using fungicides to manage Sclerotinia in soybeans:
Disease-associated yield loss, 0-maturity group
1. YIELD LOSS RELATIONSHIP OBSERVED IN FUNGICIDE TRIALS:
• 46 field trials conducted 2012 to 2015 at four sites across North Dakota
• 16 soybean varieties in the 0-maturity group (0.2 to 0.9)
• Every 10% increase in Sclerotinia incidence conferred between
1.3 and 5.5 bu/ac yield loss
2. YIELD LOSS RELATIONSHIP, IRRIGATION STUDY:
• Differences in disease levels achieved through differential irrigation intensity at R2 to R4
with total irrigation kept constant
• 14 soybean varieties in the 0-maturity group (0.2 to 0.9)
• Every 10% increase in Sclerotinia incidence conferred between
1.7 and 3.9 bu/ac yield loss
Economics of using fungicides to manage Sclerotinia in soybeans:
Economic thresholds
Assumptions:
Application cost: $27/acre ($20 fungicide + $7 application)
Disease control: 45%
Yield impact: 1.6 to 4.6 bu/ac (middle 90% of fungicide trials)
Break-even point when fungicides become profitable:
Soybeans at $8/bu: 16 to 46% Sclerotinia incidence in nontreated check strip at end of season
Soybeans at $10/bu: 13 to 38% Sclerotinia incidence in nontreated check strip at end of season
Soybeans at $12/bu: 11 to 31% Sclerotinia incidence in nontreated check strip at end of season
Economics of using fungicides to manage Sclerotinia in soybeans:
Evaluating risk
ON AVERAGE,
Susceptibility to Sclerotinia is lower
in shorter maturity varieties.
DATA from 14 varieties grown in randomized pattern with different levels of disease facilitated by dfferential irrigation; Carrington, ND (2014)
Seeding rate: 165,000 pls/ac Row spacing: 14 inches
ON AVERAGE,
The impact of Sclerotinia on yield is lower
in shorter maturity varieties.
ON AVERAGE,
Sclerotinia
is most
severe
when
cool, wet
weather
occurs
early in
bloom.
Wet conditions
delayed from
V4 to R2
growth stage:
Wet conditions
delayed from
R2 to R4/R5
growth stage:
ON AVERAGE,
Impact of
Sclerotinia on
yield
decreases when
conditions
favorable for
disease do not
occur until pod-fill.
Economics of using fungicides to manage Sclerotinia in soybeans:
Evaluating risk
ON AVERAGE,
Frequent, light rainfall confers higher risk of Sclerotinia than
infrequent, heavy rainfall.
DATA ARE FROM 14 SOYBEAN VARIETIES (0.2 to 0.9 maturity)
Varieties grown in randomized pattern with different levels of disease facilitated by dfferential irrigation; Carrington, ND (2014)
Seeding rate: 165,000 pls/ac Row spacing: 14 inches
Economics of using fungicides to manage Sclerotinia in soybeans:
Evaluating risk
ON AVERAGE,
Impact of
Sclerotinia
on yield
is lower in
soybeans
seeded to
wide rows.
Carrington, ND (2014)
Seeding rate:
165,000 pls/ac
Row spacing:
14 inches
Thank you!