Variable oilseed rape crops highlight need for pod sealants

The contrasting maturity of many oilseed rape crops raises the prospect of increased losses from pod shatter this harvest, but advisers suggest this can be greatly reduced with the inclusion of a suitable pod sealant.

According to Pro Cam agronomist Steve Wolff a suitable pod sealant such as Mesh or Pod-Stik is a ‘no-brainer’ this harvest it is has been shown to protect crops from the effects of pod shatter caused by unfavourable weather in the weeks building up to harvest and from header losses at the point of combining.

“In recent years it has been acceptable to apply Pod-Stik with the desiccant, but because of the variability of crops this year we are advising growers to make separate applications. When asked if it is a necessary application I reply in a most affirmative manner: ‘It’s a complete no-brainer’,” he says.

“Once crops reach maturity the pod becomes brittle and vulnerable to weather events such as wind, heavy rain or hail and fluctuating temperatures. These factors can result in extensive losses, or in the worst case scenario, crop decimation. Header losses caused by vibration can have the same effect,” he says.

With crops at varying stages of maturity following an extended flowering period as a result of the difficult season, he worries that growers will unknowingly expose themselves to the risk of excessive losses which could be easily and cheaply avoided.

There is no right or wrong strategy however and he is suggests tailoring the approach to crop growth stage.

“It is important to recognise that both Mesh and Pod-Stik are effective for up to 12 weeks so there is a large window of protection for growers to fall back on. Where crop variability extends beyond a week our advice is to treat the area that is further ahead first and return to the backward plants later. But where variability can be described as less than a week wait until the majority of the crop is growth stage 80-82 and apply across the whole area.”
 
Pod sealants are of equal benefit to swathed or desiccated crops, but Steve Wolff is advising against former this year as most crops are short and unlikely to provide much stem for the laid plant to rest on. This means swathed crops are likely to take longer to dry out before being fit enough to harvest.

For those who prefer to desiccate he suggests choice of product should be determined by the weed burden within crops.

“Unless there is a large volume of broadleaf weeds in need of control then diquat is likely to be a better choice this season. Glyphosate is a highly effective product, but its translocated activity means the plant needs to be alive and growing when it is applied to ensure it gives the desired effect. The variable nature of most crops means it is quite possible that some plants will be past the point at which glyphosate will be most effective. In these situations diquat will give a more consistent effect,” he says.

Where glyphosate is the preferred herbicide however, it is worth selecting a product with a recognised faster mode of action to give greater consistency.

“Roundup Max tends to be several days faster acting than glyphosate 360 and it may be all that is needed to ensure it can be harvested in good time,” he says.

De Sangosse commercial manager Simon McMunn says that Pod-Stik gives a return on investment well beyond that of most products.

“Pod sealers typically give a benefit where used, but not all pod sealers deliver the same performance. In independent trials performed in 2010 the best performing pod sealer gave a yield benefit of 0.5t/ha over glyphosate only (control) and 0.2t/ha over the next best performing pod sealer,” says Mr McMunn.

“This was repeated in 2011 where Excalibur crops treated with the best performing pod sealer yielded 4.5t/ha compared with the 4t/ha for the control and 4.2t/ha for the next best performing product.”

Weather events after crops have been desiccated have the greatest influence in determining the value of a pod sealer in protecting yield, but with oilseed rape prices for November 2013 trading at about £340/t the economic benefit of a pod sealer is clear.

“A grower enjoying a similar result to that seen in trials would see an extra £170/ha in output. Pod-Stik is available on farm for about £10/ha, giving a return on investment of 17:1 at current market prices,” he says.