Story Posted: June 29, 2011

Canola Watch: Help with sclerotinia decision, Spraying weeds late

Issues of the week: Many canola fields are under stress from excess water. A fertilizer top up may help, but hold off until the ground dries up and the crop starts actively growing again before making this investment. Rains have also delayed timely herbicide applications, so many growers are wondering about the real yield risk if they spray after the label window. The yield loss could be significant if growing conditions turn hot and dry after spraying. Plus the practice violates product labels.

Moist conditions increase the sclerotinia risk, especially since the disease was so widespread last year. Early canola crops are starting to flower, and the ideal timing for sclerotinia spraying is at 20% to 50% bloom.

Register now: We encourage growers to attend the Canola Council of Canada Combine Clinic in Westlock, Alta., July 18 or 19 to learn how to reduce harvest losses. Research and in-field evaluations have shown that canola growers lose up to five bushels per acre out the back of their combines. Click here or call 1-866-834-4378 ext. 2111 for more information and to register.

Canola Watch is brought to you with the support of Agriculture and Agri-Food Canada's Agri-Flexibility Fund.

Crop and weather update
Peace (B.C. and Alberta): South and central Peace regions got a lot of rain in the past week, with accumulations of 4" to 7". Canola in low areas is yellowing as a result of moisture stress. Crops not drowning are advancing quickly. Some canola is at 20-30% bloom. While the south is soaking, north Peace canola is under drought stress.

Alberta: The south had small showers with accumulations of 1/2" or less. Thundershowers through central Alberta dropped up to 6" in some regions and next to nothing in others. Water is ponding in areas with heavy accumulations. Early fields are at 20% flower. A few southern growers were still trying to seed canola this week. Alberta crop report.

Saskatchewan: Western Saskatchewan had spotty rain showers delivering from 1" to 3" in the past week. Crops overall look good in west and central regions, with many fields at the 6-leaf to bolting stages. In the southeast, excess moisture remains the biggest issue with another 4"-6" of rain in the past two weeks on top of what was already too much. Many seeded crops are drowning. In the northeast, saturated pockets are interspersed with some very good looking crops. Saskatchewan crop report.

Manitoba: Another 1" to 4" of rain fell in the past week. Of the fields that were seeded, many are yellowing, cotyledons are purpling, and some plants are prematurely bolting - which are typical responses to waterlogging. Staging ranges from just emerging (some growers were still seeding this week) to flowering. In general, the province needs heat for canola to cabbage out and fill in. Manitoba crop report.

What is the goal with a late herbicide spray?
Herbicide labels say that glyphosate and Odyssey cannot be applied to canola after the 6-leaf stage and Liberty cannot be applied after early bolting. These limits are in place to ensure effective product performance and crop safety. Later applications can lead to reduced weed control due to advanced weed staging and reduced herbicide contact with the weeds through the increased canola canopy closure. Late applications can also sometimes cause canola buds to abort, increasing the potential for permanent yield loss.

Yield loss from late herbicide applications vary on a field by field basis depending on herbicide rate, overall health of the field, and growing conditions during and after the application. Canola under any type of existing stress will likely have greater losses from a late herbicide application. It simply won't be able to recover as quickly. If canola is healthy at the time of spraying but conditions are hot and dry soon afterward, canola may not be able to compensate by adding more flowers later in the flowering period. Losses cannot be predicted, but they could be 30% - and even more in overlap areas.

Growers who haven't sprayed second (or in some cases first) applications because of excess moisture or wind or cool conditions should understand the risks before spraying after the label window has closed.

What is the goal with a late spray?

• Yield benefit. If canola is bolting and the canopy is filled in, then any yield benefit of a second spray is probably not enough to cover the cost of the spray. Weeds poking through the canopy have probably already done their damage, and late flushing weeds are unlikely to have much impact - and probably wouldn't be hit by the herbicide anyway if the canopy is closed in.
• Tough weed control. If growers use canola as a clean up crop for narrow-leaved hawk's beard, round-leaved mallow and other weeds tough to control in cereals, then they may consider a herbicide application after the spray window to be worth the risk of a significant loss in canola yield. Some growers with very poor looking canola crops are already looking toward next year and don't want the weeds to get away on them. Note however that these large weeds may require a higher rate for control - a rate that may exceed the in-crop maximum for the herbicide.
• Final touch up. If the second pass is to give the field a final clean up to knock out a few remaining weeds, it may not be worth the risk.

5 key questions about sclerotinia spraying
If fields are moist at the time of flowering, and canola has good yield potential (e.g. 30 bu./ac. or more), then it will probably pay to spray a fungicide to limit sclerotinia losses. Here are a few important questions about the disease:

How does sclerotinia stem rot infection occur?

Moist soils promote the growth of apothecia from sclerotia that came from previously infected plants. With higher rates of sclerotinia infection across the Prairies in 2010, and with moist soils this year, apothecia numbers will be very high. Apothecia eject spores into air and wind spreads them all over the countryside. Spore release can take place over a period of weeks, filling the Prairie air with ascospores. These spores land everywhere, but only those that land on canola petals concern us. Ascospores need dead plant tissue to continue their cycle. Petals drop off, land in the canopy and then start to decay. These decaying petals give the sclerotinia spores the energy to produce hyphae that invade stem tissue. Because most fungicide sprays do not effectively penetrate the stem tissue to eradicate infection, living flowers are the best target for fungicides to prevent sclerotinia infection.

How do I know if it pays to spray?

With widespread sclerotinia infection last year, all regions of the Prairies are at risk this year. If your fields had moist soil ahead of flowering to promote apothecia development, and rain or high humidity during and after flowering that causes petals to stick to the plant and promote fungal growth, then infection is likely. Whether a spray pays is more difficult to answer, but moist conditions and high yield potential will likely create a favorable economic payback from a fungicide application. The sclerotinia checklist (posted at the bottom of this article) from the Canola Council of Canada's Canola Scouting & Disease Risk Assessment Card can help with the decision.

Should fungicide be applied early, late or both?

Timing should be within the window from 20% to 50% bloom. (Some products are registered for only 20% to 30% bloom.) At 20% bloom, no petals have dropped and no pods are forming. At 30% bloom, petal drop has just begun and side branches are just starting to bloom. Canola can reach 20% flower in 4-5 days after first flower, so prepare to assess the sclerotinia stem rot risk as soon as flowering starts.

Spraying at 20% to 30% bloom ensures that a large number of flowers have opened and the spray will cover petals before they drop. But if conditions are dry at early flower and then it rains at 40-50% flower, then a later application may be more effective. Split applications (two lower rate applications 7 to 14 days apart) can be worthwhile if conditions are good for fungal growth and the crop flowers for a long period. Split applications might also be best for crops with plants at multiple stages. The first application can be made when the first plants reach recommended staging. If necessary, a second application can be made when the remaining plants are ready to be sprayed. Not all products are registered for a split application.

Are thin stands at lower risk?

Not necessarily. Conventional wisdom would be that with fewer plants per square foot, the canopy would be more open, less humid and at lower risk of infection. This might be true for a thin canopy with low yield potential. But if a canopy of 2-3 plants per square foot fills in, it will have very large plants with lots of leaf material and a longer flowering period. This could actually increase the risk of yield loss from sclerotinia because the crop is flowering longer and dropping petals into the canopy over a longer period. With larger leaves, these plants have more surface areas for petals to land.

What products are registered for in-crop sclerotinia control in canola?

Astound. Apply at 20-30% bloom. Only one application.
Lance. Apply at 20-50% bloom. Can apply second application 7-14 days after the first.
Proline. Apply at 20-50% bloom. Only one application.
Quadris. Apply prior to 30% bloom. Only one application.
Rovral. Apply at 20-50% bloom. Splits are allowed.
Serenade. Apply at 20-30% bloom and again 7-10 days later around 50% bloom if necessary.

All products are registered for aerial application.

	The checklist is from the Canola Council of Canada's Canola Scouting & Disease Risk Assessment Card. Click here to download the card.

Click here to hear an interview with Alberta Agriculture canola specialist Murray Hartman on sclerotinia.

Insect update: Lygus bugs and cabbage seedpod weevil
Lygus: Lygus bugs are feeding on canola in the Peace River region and in some parts of central Alberta. Insecticide control at the bud stage is rarely effective or economical. Under good growing conditions, canola can grow through this early damage without any yield loss. Instead of spraying, step up monitoring and proper sweep net sampling and be ready to take action at the pod stage if necessary. The tables below show thresholds for early and late podding. Click here for more on the current lygus situation.

Cabbage seedpod weevil. Adults have arrived and are feeding on volunteer canola at the bloom stage in southern Alberta and southwest Saskatchewan. Weevils move to canola fields at the bud to early flower stages. Growers should start scouting.

The proper way to sample for cabbage seedpod weevil adults is with a sweep net. Begin sampling when the crop first enters the bud stage and continue through the flowering period. Select 10 locations within each field and at each location, count the number of weevils from ten 180° sweeps. Sample both the perimeter and interior of the field to obtain an accurate estimate of weevil numbers throughout the field. Click here for more detailed information on proper sampling techniques.

The economic threshold for the weevil is 20 to 30 in 10 sweeps, depending on crop price.

It is important not to spray too soon, as the weevil will typically continue to invade for at least a week to 10 days after the first flowers open. The optimum time to spray for cabbage seedpod weevil is early flowering (10% flower if possible). Spraying at 10% flower will allow the weevils more time to move into the field, while at the same time it is still early enough to keep them from laying any significant number of eggs in the newly forming pods. Spraying after 10% flower when populations are at or above threshold may not only result in yield loss, but will also impact beneficial insects including pollinators who have moved into the field. It is important to keep in mind canola's ability to compensate for weevil feeding on buds and stems where moisture is not limiting. Where moisture constraints are present, the ability to compensate may be reduced, and using the lower end of the threshold range may be appropriate. The Prairie Pest Monitoring Network provides identification and more monitoring tips: 2010_CSPW protocol

Scott Meers of Alberta Agriculture & Rural Development is recruiting scouts and crop consultants to enter cabbage seedpod weevil data into an online survey. This data will populate a google map that will show weevil hotspots in real time. Call 310-2777 and provide name, sample date, location (LLD or GPS), total number of sweeps, and total number of weevils in those sweeps.

Grasshoppers: Rain does not seem to be setting back the grasshopper threat in the Peace Region. Some growers are having to spray. The Prairie Pest Monitoring Network's models predict the grasshopper hatch is more or less complete. Across the Prairies, 85% of the population is predicted to be in the first or second instar.

Fungicide and insecticide tank mixes
Growers in southern Alberta and southwestern Saskatchewan often spray for cabbage seedpod weevil at 20% flower. This is also an ideal time for sclerotinia spraying if conditions warrant a spray.

Canada's crop protection rules allow growers to tank mix two products as long as they are both registered for the crop in question and at the timing and rates used. But these rules do not ensure these products can be mixed without problems in the tank (they may create a gummy mixture that ruins the sprayer) or without antagonizing each other (both products becoming less effective.) Growers are advised to ask the retailer or the crop protection company before trying a tank mix for the first time.

Of the six products registered for sclerotinia management in canola, only one has a registered tank mix with insecticide. That is Astound with Matador. Serenade, which has a biological active ingredient, explicitly says "Do not tank mix with pesticides."

The key with any tank mix is to make sure both products are in fact needed. It may be convenient to tank mix because you're going over the crop anyway, but applying an unnecessary product adds to the cost without providing a benefit to justify this cost. It could also cause future problems by reducing levels of beneficial organisms which regulate potential pests.

Top dress canola with sulphur deficiency
Some canola fields are showing signs of sulphur deficiency. In many cases, the fields have ample nitrogen, but are short on sulphur. Without enough sulphur, it doesn't matter how much of the other nutrients are available, the canola crop cannot produce top yields.

Post-emergence sulphur can be applied up to early flowering and still provide a yield benefit.

With sulphur deficiency, yellowing and leaf cupping tend to occur on new leaves first. Purpling of leaf edges can show up when deficiency is fairly severe. In fields short of sulphur, crops can usually find enough to get past the early rosette stage without visible symptoms. Deficiency symptoms often show up at flowering, which can be helped if detected early. Growers who suspect they may face a sulphur deficiency may want to take action now. (Click here and scroll down to the sulphur section for examples.)

Ammonium sulphate (dry) or ammonium thiosulphate (liquid) provides sulphur that is immediately available to the crop.

	Purpling around leaf edges is one sign of possible sulphur deficiency.

Be skeptical of miracle cures. High yielding canola needs large amounts of N, P, K and S. Crop nutrition products that claim to meet canola's needs without supplying the pounds of nutrient required should be regarded with skepticism.

Fertilizers are registered through the Canadian Food Inspection Agency (CFIA), but not all crop nutrition products are registered. Controlled release coatings, urease inhibitors and inoculant extenders, for example, do not fall under the regulatory authority of the Fertilizers Act. When these are mixed with a fertilizer, the end product is regulated, unless the enhancers or extenders are put into a custom fertilizer blend (in which case registration is not required).

The CFIA's Crop Inputs Division "encourages" manufacturers of these products to seek a "Letter of No Objection" (LONO) from the CFIA to ensure that their use in fertilizers and supplements results in final products that meet safety, efficacy and labelling standards. This is something growers can request if they are looking for additional assurance related to claims made by providers of these products.

For more on top dressing, click here and here.

Return unused seed for a refund
Seed companies encourage growers to return unused unopened bags of canola seed. That way the seed company can ensure that seed is stored properly to maintain its high quality. Growers get their money back. At least one company has a deadline of June 30, so if you have seed to return, you may want to check right away.

Can't deliver on a contract? Growers with delivery contracts they will not be able to fulfill due to unseeded or flooded acres should contact the company now. Early action will help growers find the best course of action. Click here for a Canadian Canola Growers Association article on "What to Consider if Production Comes Up Short on a Forward Priced Contract."

Coming events
CCC Webinar: Sclerotinia Preview with Clint Jurke, CCC agronomy specialist. June 30 at 10:00 a.m. CDT. Click here to register.

Crop Diagnostic School in Carman, Manitoba is July 5-8 and July 11-15. Click here for more information. To register call 204-745-5663.

Farming Smarter diagnostic field school is July 5-7 in Lethbridge, Alta. Choose one day. Click here for more information and a registration form.

Conservation Learning Centre tour, July 12 at Prince Albert, Sask. For more information, call Curtis Braaten at 306-960-1834 .

Wheatland Conservation Area and AAFC tour, July 12 at Swift Current, Sask. For more information, call Shannon Chant at 306-778-8291

AAFC and Western Applied Research Corporation's Scott Field Day in Scott, Sask., is July 13. The morning tour is from 9:00 to 12:30 and the optional afternoon tour is 1:30 to 3:00. Canola topics include inputs to target high yield, seeding speed and its impact on emergence, and canola variety shatter resistance. For more information, contact Sherrilyn Phelps at 306-446-7475.

CCC Webinar: Sclerotinia Management in 2011 with Faye Dokken Bouchard, plant pathologist with Saskatchewan Ministry of Agriculture. July 14 at 10:00 a.m. CDT. Click here to register.

Canada-Saskatchewan Irrigation Diversification Centre tour, July 14 in Outlook, Sask. For more information, call Gerry Gross at 306-867-5523

Combine Clinic. The Canola Council of Canada and Alberta Canola Producers Commission will host a Combine Clinic in Westlock, Alta., July 18 and 19. Click here to register.

AAFC and Indian Head Agricultural Research Foundation tour, July 19 in Indian Head, Sask. For more information, call 306-695-4200

Southeast Research Farm tour, July 20 in Redvers, Sask. For more information, call Elaine Moats at 306-848-2856

Crop Protection Field Day (University of Saskatchewan and AAFC), July 20 at Kernen Research Farm, Saskatoon. To pre-register, call at 306-966-5857

AAFC and Northeast Agriculture Research Foundation tour, July 21 at Melfort, Sask. For more information, call Kim Stonehouse at 306-878-8807 .

East Central Research Foundation tour, July 21 at Canora, Sask. For more information, call 306-788-1508.

The Canola Council of Canada's Convention is July 26-28 in Saskatoon. The theme is "Global Farmers. Global Markets." Click here for more information and to register.

« Back to main Latest News page