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Using pod sealants

Looking for a way to keep canola pods from shattering during the harvest? 
Pod sealants may not be a magic cure, but they could provide peace of mind

When pod sealants arrived on the market in Western Canada a few years ago there was considerable interest from farmers who were experiencing problems with pod shatter in canola.

Pod shatter is a big concern when straight combining canola, especially if harvest is delayed. There have been reported yield losses up to 50 per cent relative to swathing in some straight-combined canola crops due to pod shatter.

Pod sealants

Pod sealants are sprayed on the crop to form a coating that is designed to reduce the risk of pod shatter as the seeds inside mature. It’s generally recommended that pod sealants be applied when approximately 30 to 40 per cent of the pods have changed colour, but are still pliable and not brittle.

“Our product label states that it should be applied between growth stage 80 (seed green, filling pod cavity) until growth stage 89 (fully ripe, seeds are black and hard),” says Dale Ziprick, product manager with UAP, which markets Pod-Stik, manufactured by Loveland Products Inc., one of only two pod sealants currently available in western Canada. “But earlier is better because if you are going in with a ground rig you run the risk of some seed shatter on the more mature pods.”

Research done to date in both North Dakota and Saskatchewan has not been able to prove any significant benefits from the use of pod sealants in straight-combined canola crops. There are some obvious advantages, one being that the cost of the product, plus application is similar to the cost of swathing and can be done more quickly than swathing.

But in terms of saving yield by preventing pod shatter, results from recent trials in Saskatchewan haven’t been all that promising.

Saskatchewan studies

Studies were initiated in 2009 and 2010 at four locations; Melfort, Indian Head, Scott and Swift Current. The field trials included five canola cultivars and four harvest treatments: swathed, straight-cut with no pod sealant, straight-cut with Pod Ceal DC (a product formerly distributed by Brett-Young) and straight-cut with Pod-Stik.

The study showed that total seed losses due to pod shattering and whole pods dropping, just prior to harvest, ranged from less than one per cent of the total yield to over 22 per cent at one site at Melfort in 2010 when extreme conditions (snowfall prior to harvest) were encountered. The pod sealants did not have a measurable effect on shattering losses, even under moderate to high shattering conditions. On average, losses for all cultivars were six per cent of the total yield at the time of harvest.

Straight-combining resulted in a small but consistent and significant increase in seed size (six per cent on average), but pod sealants did not appear to have any effect on seed quality.

The study did detect a positive impact on canola yield, but only at one site. “We saw a positive yield response to pod sealants at one of eight sites and the increase was on the order or 15 per cent,” says Chris Holzapfel, research manager at Indian Head Agricultural Research Foundation, who was involved in the study. This benefit was observed at a site where moderate but not excessive shattering losses occurred. “However, because we did not see a response almost 90 per cent of the time and I see no real way of being able to predict the likelihood of seeing that type of response [with any regularity], it is difficult for us to recommend using pod sealants based on this data.”

UAP held its own side-by-side trials in 2008 with 26 farmers across Western Canada. UAP’s results showed an average yield increase of two bushels per acre in canola across all the sites, with a positive yield response in 14 of the 26 sites and no response in 11 sites. Only one site showed a negative yield response.

Pod shatter in canola

It’s important to remember, says John Mayko, a senior agri-coach with Agri-Trend, that pod shatter in canola has a lot to do with the whole crop condition. “Generally speaking, what we recommend is the crop has to be a good candidate for straight cutting,” he says. “It’s got to be a crop that’s healthy, disease free and is well knitted together, not a light, spindly crop. If you are already behind the eight ball with a crop that is more at risk of shattering, I don’t see that spending money on a pod sealant is a good investment.”

Pod shatter can sometimes be mistaken for other problems, especially if there are disease problems in the crop, adverse weather conditions or other conditions that can cause pod loss.

“Another risk that people generally don’t talk much about is pod drop,” says Mayko. “That’s where the pod breaks off at the stem that attaches it to the main stem of the plant. People look at seed loss and assume that most of it is due to pod shatter, but there is also pod drop and pod sealants aren’t going to help with that.”

Holzapfel’s data suggests that pod drop losses can frequently contribute to up to 50 per cent of the total environmental seed losses that occur under field conditions, which may partly explain why they didn’t see a yield benefit very often.

Ziprick feels that there has definitely been some confusion in the marketplace about what pod sealants are designed to do. “The biggest thing that we have to remember with this product is it’s not a be-all, end-all solution that stops shattering in its tracks,” he says. “Pod-Stik is a latex based product, that when applied to the plant, will provide a netting over the pod preventing it from splitting, while allowing moisture to move freely for normal maturity development. What it doesn’t do is eliminate the risk of the pods physically dropping off the plants. When these products were brought to the market I think they weren’t completely understood in that context. Pod-Stik will remain effective for up to eight weeks post application, but the best advice I can give is to harvest the crop as soon as it is ready to do so.”

Applying pod sealant

It’s important to know how to properly apply pod sealants, adds Mayko. In his experience some farmers have had disappointing results, which he attributes to not getting enough coverage from the product. “It’s generally recommended that these products have to be applied with 15 to 20 gallons of water,” says Mayko. “It’s a contact product, so the more water you can apply the better coverage you will get. If you are going to be cheap on the water then the suggestion is you don’t bother applying these products because you are going to be disappointed with the results.”

UAP’s side-by-side trials incorporated different application methods at different water volumes. Based on that data, Ziprick recommends that farmers do not go lower than 10 to 15 gallons per acre with a ground sprayer and no lower than five gallons by air. Applying a higher water volume is essential as the density of the crop canopy increases to ensure good penetration and coverage to the pods situated on the lower part of the plant. “To maximize coverage you also need to use a nozzle that will give a medium quality spray,” says Ziprick.

Choosing the right variety is probably a more important factor of resistance to shattering than the use of pod sealants. In Holzapfel’s study there were significant differences in shatter resistance between varieties. He suggests that choosing high yielding cultivars that are relatively resistant to pod shattering will offer canola growers considering straight-combining a greater advantage than using pod sealants.

Ziprick agrees that pod sealants are not a silver bullet, but they do offer another risk management tool for farmers to consider, especially when Mother Nature doesn’t co-operate.

While the focus with pod sealants has been largely been as a tool for straight cutting canola, Ziprick sees an opportunity for farmers who still choose to swath all or some of their canola to use Pod-Stik just prior to swathing. “The fact that more farms are growing larger acres of canola, trying to manage the timing and the variability that exists within fields and between varieties, we see this as an excellent risk management tool if used correctly,’ says Ziprick. “At the end of the day it adds that layer of insurance to the whole approach of managing harvest losses.” †

The growth stages Dale Ziprick refers to in this article are described on the Canola Council of Canada’s website. These numbers are part of the BBCH decimal system — a standard approach developed by BASF, Bayer, Ciba-Geigy and Hoechst.

The system divides plant growth into the following categories.

  •  0: Germination
  •  1: Leaf development
  •  2: Development of side shoots
  •  3: Stem elongation
  •  4: Not key to canola development
  •  5: Inflorescence emergence
  •  6: Flowering
  •  7: Seed development
  •  8: Ripening
  •  9: Senescence

No. 8, ripening, is further divided into several distinct stages:

  •  80: ripening begins — seed green, filling pod cavity
  •  81: 10 per cent of pods ripe, seeds black and hard
  •  82: 20 per cent of pods ripe, seeds black and hard
  •  89: fully ripe, nearly all pods ripe, seeds black and hard

Find full descriptions of all of these growth stages on the Canola Council of Canada’s website (www.canolacouncil.org.)

This information is in Chapter 3 of the Growers’ Manual. †

About the author

Contributor

Angela Lovell

Angela Lovell is a freelance writer based in Manitou, Manitoba. Visit her website at http://alovell.ca or follow her on Twitter @angelalovell10.

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