Variable OSR crops require tailored protection – Expert ProCam
Mike Thornton, agricultural production manager for agronomy company ProCam, told The Scottish Farmer that expected high prices of around £600/tonne would justify investing in monitoring rapeseed crops this spring and this summer.
However, variable growth will mean that management will need to be tailored to individual estates. “Much of the winter rapeseed (WOSR) appears to have escaped significant cabbage stem flea beetle damage this season,” Thornton said.
“But pigeon damage in some fields has been terrible, and crop heights range from barely above the ground to almost knee-high. Where pigeon-damaged crops have decent root structures , they have a chance to recover.
“It will be important to ensure that recovery is not hampered by lack of nutrients. Severely affected crops may need supplemental nitrogen (N), especially in the worst parts of the field and it will be important to avoid micronutrient deficiencies, especially boron and molybdenum. ”
In all WOSR crops, Mr Thornton added that it will be vital to keep pigeons away to prevent them from browsing on flower buds. Any crop that has suffered delayed flowering due to pigeon damage could be severely infested by pollen beetles later on, while crops that flower unevenly make it difficult to precisely time sprays of sclerotinia fungicide, a he pointed out.
“In advanced WOSR crops, canopy size may need to be regulated as temperatures increase and days lengthen, not only to reduce the risk of lodging, but also to open up the canopy to allow in the light to enter.
“If you also need to target mild leaf spot or phoma infections, canopy management can be achieved at the same time using a combination treatment of an appropriate fungicide with a plant growth regulator. It will also help to even out the harvest,” he said. noted.
“So far, although outbreaks of mild leaf spot appear to be sporadic, they have been reported in Oxfordshire and traditionally higher pressure further north in Scotland means that even the most resistant varieties can be severely affected. It is important to be vigilant because the moment the leaf spot becomes visible, control becomes more difficult.
“Unusually this season, phoma, which is traditionally more of a southern disease, is being reported in Scotland, so it may also need to be considered in fungicide choice.”
To preserve yield potential during flowering, he called for similar vigilance against sclerotinia, botrytis and alternaria infections. Although these are highly dependent on weather conditions, he says most fungicides work preventatively, so again, timely application is essential.
“After the mild winter, another disease reported this year is clubroot. There is not much that can be done about this at this stage, although applying a calcium carbonate top dressing to raise the soil pH is an option, and it is important to take good care of the crop nutritionally, as nutrient uptake via the deformed roots of infected plants will be limited. Mr. Thornton added.
“For the future, however, what you can do is note which fields are affected. Doing so helps with longer term management – including rotation planning, liming of infected fields, choice of more tolerant varieties and delaying WOSR sowing.”
Once the OSR is in flower, Mr Thornton urged to be wary of pollen beetles. Although normally less of a problem for winter rapeseed than spring rapeseed, he told WOSR that later blooms will be more susceptible.
“If you’re treating beetles, do it only according to pest thresholds – we need to use insecticides sparingly to protect against resistance,” he said.