managing sclerotinia in soybeans with fungicides sclerotinia in soybeans with fungicides . 1....

Michael Wunsch, PhD

North Dakota State University - Carrington Research Extension Center

Managing Sclerotinia in soybeans

with fungicides

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


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


FOR CONTROLLING OR SUPRESSING SCLEROTINIA

ON SOYBEANS BUT NOT CANOLA:

Allegro (fluazinam)

Stratego Pro (prothioconzole + trifoxystrobin)

Registered fungicides – canola vs. soybeans

Application rates:

Lance:

145 – 164 ml/ac

Proline:

148 – 159 ml/ac

Fungicide efficacy – importance of fungicide coverage

Non-treated

Lance

Proline

Non-treated

Lance

Proline

Application rates:

Lance:

170 – 227 ml/ac

Proline:

169 ml/ac

Fungicide efficacy – importance of fungicide coverage

Non-treated

Lance

Proline

Non-treated

Lance

Proline

Fungicide efficacy – canola

Sclerotinia

severity

index (%)

Yield

(lbs/ac)

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

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 (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

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

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

2. LANCE:

Not registered in Canada, but the competitive standard in the United States.

• Average reduction of Sclerotinia with R2 applications: 45%

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


Disease-associated yield loss, 0-maturity group

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

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


Economic thresholds

Break-even point when fungicides become profitable:

Soybeans at $8/bu: 16 to 46% Sclerotinia incidence in non-

treated check strip at end of season





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)


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.

Wet conditions

delayed from

V4 to R2

growth stage:

ON AVERAGE,

Sclerotinia

is most

severe

when

cool, wet

weather

occurs

early in

bloom.

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.


Evaluating risk

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

ON AVERAGE,

Frequent, light rainfall confers higher risk of Sclerotinia than

infrequent, heavy rainfall.


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!

managing sclerotinia in soybeans with fungicides sclerotinia in soybeans with fungicides . 1....

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