Sclerotinia fungicide: Timing and performance tips

Fungicide to prevent sclerotinia stem rot goes on between 20 and 50 per cent flower, with optimum timing usually closer to 20 per cent.

In Fungicide application basics, Sprayers 101 says the two top considerations for effective fungicide applications, in general, are timing and water volume.

Canola in the sclerotinia fungicide window

Timing

Apply within the spray window of 20 to 50 per cent flower. The early opportunity, at 20 per cent flower, usually provides a higher economic return – if moisture conditions favour infection.

How to assess the bloom stage. Generally, it takes a crop four to five days to move from first flower to 20 per cent bloom.

Fungicide applied at the beginning of the label window will coat the petals that are there, and provide important coverage down in the canopy.

Earlier-than-label applications that target buds before they open to form flowers provides minimal benefit given the limited systemic action of the fungicides available for canola. They would not typically penetrate from the green sepal tissue into the petal tissue itself.

Coverage

Fungicide should cover as many petals as possible.

Water volume at label-recommended amounts improves coverage of flower petals and penetration down into the canopy.

Fungicide that also hits leaves, leaf bases and leaf axils – where infested petals clump – can enhance protection. Higher water volumes improve penetration and coverage of these canopy targets.

Fungicide duration

Fungicide protection in the canopy can last two weeks or more. Flower petals have a six-day life cycle. If you were to focus on applying fungicide on petals themselves you would need to repeatedly apply fungicide to coat each successive crop of newly emerged flower and petals.

The actual length of fungicide protection will depend on the product and its persistence, as well as the quality of application and its penetration into the canopy. For second fungicide applications, the recommendation is to wait seven to 14 days after the first application.

Fungicide mode of action

Most fungicides available for canola are locally systemic – they only penetrate into the outside layers of the plant tissue applied to. Some do move a bit more extensively, such as from one side of a leaf to another, or even from the centre of a leaf to the tip. (See the illustration at the bottom.)

Some fungicides are more lipophylic than others. This “love of fats” might be more advantageous than systemic activity. Lipophylic fungicides will bind to the waxy cuticle, keeping the active ingredient on the leaves and fighting the disease.

Fungicides for sclerotinia stem rot in canola

Product	wdt_ID	Company	Group	Active Ingredient	Rate (per acre)	Application stage
Acapela	1	Corteva Agriscience	11	250 g/L picoxystrobin	325 to 485 mL	20 - 50% bloom; Under high disease pressure make second application 7 - 14 days later with difference from difference fungicide group.
Azoshy250 SC	2	Sharda Crop Chem Canada	11	250 g/L azoxystrobin	280 to 400 mL	prior to 30% bloom; Use higher rate with past sclerotinia history in area and when conditions favour development
Cotegra	4	BASF Canada	3, 7	250 g/L boscalid, 150 g/L prothioconazole	240 to 280 mL	20 - 50% bloom. Rate is determined by relative disease pressure and risk of disease development. Apply second application 7 - 14 days later if disease risk persists
Dyax	5	BASF Canada	7, 11	250 g/L of fluxapyroxad, 250 g/L of pyraclostrobin	120 to 160 mL	20 - 50% bloom. Use high rate under high disease pressure. If disease risk persists, make a second application 10 - 14 days later with a different mode of action
Evito 480	6	UPL AgroSolutions Canada Inc.	11	480 g/L fluoxastrobin	59 to 118 mL	20 - 50% bloom, or prior to petal drop. Follow with second application as needed on a 7 - 14 day interval. Use high rates and shorter interval if disease pressure is high.
Lance AG	7	BASF Canada	7, 11	70% boscalid (A); 250 g/L of pyraclostrobin (B)	132 mL (A); 140 g (B)	20 - 50% bloom
Lance WDG	8	BASF Canada	7	70% boscalid	140 g	20 - 50% bloom. Apply a second time 7 - 14 days later up to full bloom if disease persists or if weather conditions are favoruable for disease development
Miravis Bold	9	Syngenta Canada Inc.	7	200 g/L of pydiflumetofen	405 mL	10 - 50% bloom
Priaxor	11	BASF Canada	7, 11	167 g/L of fluxapyroxad, 333 g/L of pyraclostrobin	180 mL	20 - 50% bloom
Proline 480 SC	13	Bayer	3	480 g/L prothioconazole	125 to 150 mL	20 - 50% bloom, prior to petal drop. Use high rate if history of heavy disease or dense crop stand.
Proline Gold	14	Bayer	3, 7	200 g/L of fluopyram, 200 g/L of prothioconazole	253 mL	20 - 50% bloom, prior to petal drop
Quadris	15	Syngenta Canada	11	250 g/L azoxystrobin	280 to 400 mL	prior to 30% bloom; Use high rate if there is history of sclerotinia in the area or conditions favour disease development
Quash SC	17	Valent Canada distributed by Nufarm Agriculture Inc.	3	480 g/L of metconazole	59 to 118 mL	20 - 50% bloom; Use high rate under high disease pressure. Do not make more than one application per year
Quasi	18	AgraCity Crop & Nutrition Ltd.	11	250 g/L azoxystrobin	280 to 400 mL	prior to 30% bloom; Use high rate if there is history of sclerotinia in the area or conditions favour disease development
Serenade OPTI	25	Bayer	44	1.31 x 10^10 CFU/g Bacillus subtilis (QST 713 strain)	0.1 - 0.4 kg/ac	20-30% bloom; Use high rates if there is history of heavy disease pressure, a second application may be made at 50% bloom 7 - 10 days later prior to significant petal drop
SHAFT Fungicide	27	Sharda Crop Chem Canada	7	70% Boscalid (wettable granule)	140 g	20 - 50 % bloom. Make a second application 7 - 14 days later if disease persists or if weather conditions are favourable for disease
Holdfast	21	WinField United Canada	3	480 g/L prothioconazole	125 to 150 mL2 (for 480 g/L products)	20 - 50% bloom, prior to petal fall. Use high rate if history of heavy disease or dense crop stand
Serenade SOIL	26	Bayer	44	1 x 10^9 CFU/g Bacillus subtilis (QST 713 strain)	0.4 to 1.6 L	20 - 30% bloom
EMISSARIUS	24	UAP Canada	11	250 g/L azoxystrobin	280 to 400 mL	prior to 30% bloom
Soratel	23	ADAMA	3	250 g/L prothioconazole	240 to 280 ml	20 - 50% bloom, prior to petal drop, use high rate if history of heavy disease or dense plant stand
Viatude	29	Corteva Agriscience	3, 11	187.5 g/L picoxystrobin, 62.5 g/L prothioconazole	0.3L or 300 ml	Begin applications before or at onset of infection. 20% - 30% bloom (no later than 50% bloom)
Advantage Prothioconazole 480 SC	31	Advantage Crop Protection Inc	3	480 g/L prothioconazole	125 to 150 mL	20 - 50% bloom, prior to petal drop. Use high rate if history of heavy disease or dense crop stand.
Joust	32	NuFarm Agriculture	3	250 g/L prothioconazole	240 to 280 ml	20 - 50% bloom, prior to petal drop, use high rate if history of heavy disease or dense plant stand.
LALSTOP Contans WG	33	Lallemand Plant Care, distributed by UAP	Biofungicide	5.00% Coniothyrium minitans strain, minimum 1x10^9 CFU/g	400 to 800 g (when incorporated in top 5 cm of topsoil), 800 to 1600 g (when incorporated into soil deeper than 5 cm)	preplant and post harvest (3 months before onset of disease symptoms if treated in the spring). Incorporation should take place as soon as possible after application (within 1 week)
Maxentis	34	Adama Agricultural Canada	3, 11	120 g/L azoxystrobin, 90 g/L prothioconazole	443 mL	20 - 50% bloom
Miravis Star	35	Syngenta Canada Inc	7, 12	150 g/L fludioxinil, 100 g/L pydiflumetofen	400 mL	10 - 50% bloom
Pavise 480SC	36	Albaugh	3	480 g/L prothioconazole	125 to 150 mL	20 - 50% bloom, prior to petal fall. Use high rate if history of heavy disease or dense crop stand
Razor 250 SC	37	Albaugh	11	250 g/L azoxystrobin	280 to 400 mL	prior to 30% bloom, use high rate if there is history of sclerotinia in the area or conditions favour disease development
VIKING Azoxystrobin	38	Viking Crop Production Partners Inc	11	250 g/L azoxystrobin	280 to 400 mL	prior to 30% bloom, use high rate if there is history of sclerotinia in the area or conditions favour disease development

Sprayer nozzles

Nozzle choice is less important for sclerotinia stem rot fungicides. Research at AAFC Saskatoon (Kutcher and Wolf, 2001) compared five methods of fungicide application over three years to determine the effect of nozzle type and pressure on sclerotinia stem rot infection of canola and crop yield.

Variation in product performance among years indicated that environmental conditions had a major effect on crop development, sclerotinia stem rot infection, the effect of fungicides and subsequent yield.

Overall, conventional flat fan nozzles (TeeJet XR), low-drift venturi nozzles (CFFC TurboDrop) and hollow cone nozzles (TeeJet TXVS-8) were all effective at reducing disease symptoms. Both 275 and 550 kPa (40 and 80 psi) provided similar performance, although increasing the venturi nozzle pressure to 550 kPa (80 psi) improved disease control slightly.

These results indicate that venturi nozzle technology is appropriate for use with foliar fungicides for sclerotinia control in canola provided pressures are adjusted to optimize nozzle performance.

Research shows minimal effect from droplet size. Sprayers 101 makes this statement: “Work at AAFC in Melfort compared conventional and low-drift sprays at two pressures, and showed that droplet size had no effect on disease control. In fact, the fine spray produced by hollow cone nozzles at high pressure did not significantly improve sclerotinia control compared to a venturi nozzle at its recommended pressure of about 60 psi.”

Aerial application

Many fungicides allow for aerial application. Sprayers 101 notes that an aircraft’s chief advantage is to cover large areas with no crop trampling, and can do so even in wet conditions. As a result, they offer the timing advantage that is so important.

Sprayers 101 expands on the aerial option: Aircraft, out of practical necessity, apply less water and distribute it in finer sprays to offer the required coverage. Although this has been shown to be effective, it creates drift and evaporation potential. It is worthwhile to ask for higher water volumes if it means that the spray can be applied somewhat coarser, creating less drift.

Ideal weather for spraying

Hot conditions can increase evaporation of the spray, reducing its performance. Some companies say to avoid spraying in temperatures above 25-27°C.

Coarse spray droplets, in this case, will help to reduce rapid droplet evaporation while still maintaining very good target coverage.

Rainfastness varies by product. Some can be applied as little as 30 minutes before a rain. Others are recommended to have at least three hours before a rain. Also use the appropriate nozzle filter screens to improve fungicide performance. Ask the retail or check labels for specific notes on filter screens.

How different fungicides provide protection on a leaf. Source: Kelly Turkington, AAFC

*Thanks to Kelly Turkington, plant pathologisit with AAFC, for help with this article.

More…

Canola Encyclopedia section on sclerotinia stem rot management.
Factors in the sclerotinia spray decision

Mobility table for common fungicides