We know that growing oilseed rape can be challenging so we have gathered together everything you need to know about oilseed rape here. From establishment to harvest we can provide insight about crop management and protection to help maximise yields.
Posted 2 years ago
March
Increasing day lengths and warmer temperatures in March means that oilseed rape crops will begin a period of rapid growth and stem extension.
The snow and frost over winter has caused defoliation, and some crops are coming out of winter looking weathered. In some places this is no bad thing, since crops were looking quite forward coming out of autumn and many will grow away strongly with the improving weather. Some crops which struggled to get established, or have suffered significant winter damage, may benefit from an application of nitrogen as a priority, to help them grow away.
Stem extension is a key timing for light leaf spot infection, so growers will need to closely monitor crops for the tell-tale tiny sugar-like spores on the leaf surface. It’s important to intervene quickly if disease is present, to prevent spores moving up the stem to the pods via rain-splash.
If you’re unsure of disease symptoms, use Bayer’s SpotCheck service to help identify whether disease is present, and justify any subsequent fungicide decisions. This initiative is helping to identify high levels of light leaf spot across the county, with 92% of the 195 samples assessed in February, showing signs of disease.
Choose a robust fungicide, that targets light leaf spot, such as Proline. This is particularly suitable for any backward crops, since Proline doesn’t have any plant growth regulation effect and therefore won’t provide any check to crops struggling to catch up. For those crops requiring some PGR activity, tebuconazole can be added to Proline where necessary.
With crops entering a rapid growth phase it’s important to use sufficient water volume to penetrate the canopy and provide adequate coverage for disease control.
There have been reports of Cabbage Stem Flea Beetle larvae in stems and damage from Rape Winter Stem Weevil larvae. The two species differ by Cabbage Stem Flea Beetle larvae having legs. Any stunted plants with side shoots may be affected. At this stage there is nothing to be done to control the larvae, but fields should be monitored, and noted for future cropping.
February
The main focus during February for oilseed rape growers is monitoring for disease. Not much spraying was achievable in January, but light leaf spot in particular may continue to infect crops if the weather remains wet.
Phoma re-infection is less likely in February, so attention should turn to monitoring crops for signs of light leaf spot. If temperatures rise going into late winter and rainfall continues, this will provide the ideal conditions for light leaf spot infection and spread.
At the early stage of infection it is very difficult to find visible signs of light leaf spot on leaves. Small, sugar-type spores can occur on the top or underside of leaves, but may be sporadic through the crop and are easily missed.
Growers can make use of Bayer’s SpotCheck service to aid their crop monitoring, and is particularly useful in more susceptible varieties. Samples of leaves are incubated to speed up the visible expression of disease, which helps to justify fungicide decisions.
There is no threshold for light leaf spot until stem extension and fungicides only work as protectants. Any autumn-applied fungicides will have run out of steam by now, so growers should aim to spray as soon as infection is identified and ground and weather conditions allow.
Proline will protect against light leaf spot, and any remaining Phoma.
Priorities now:
January
January can provide an opportunity to catch-up on tasks that weren’t completed in November or December, before crops start growing-away again.
Black-grass control is one of these priorities. If planned herbicides such as propyzamide or carbetamide haven’t been applied yet, growers have until the end of January for propyzamide and the end of February for carbetamide to do so, ground conditions permitting. Whenever these products are applied, it is important that growers remember to ensure no heavy rain is forecast in the following 48 hours after application and they follow best practice guidelines for these products to minimise the risk of pesticides reaching water.
Growers should also be monitoring for disease. Relatively high incidence of light leaf spot was observed in December, with 78% of samples received by Bayer’s SpotCheck service in December testing positive for the presence of the disease. This is higher than levels of incidence observed in 2019, and the results are spread across the UK, from Scotland to the south coast of England.
Fungicides with activity against light leaf spot act as protectants, and there is no threshold for spraying before stem extension. Growers should monitor crops closely and spray as soon as possible after infection is identified. SpotCheck can help to identify early, latent-stage infection in the crop, which can support spray timing decisions.
Growers should also watch for Phoma re-infection.
If a Phoma-specific fungicide was applied in the autumn, switching to Proline with activity against both Phoma and light leaf spot can be an advantage from January onwards.
If Proline was applied early in the autumn against Phoma and/or early light leaf spot infection, a top-up is now likely to be required, when symptoms are spotted.
Priorities now:
November/December
The majority of crops are now well established, with October’s wet weather boosting soil moisture to help struggling crops grow away from Cabbage Stem Flea Beetle damage. Some early-drilled crops are looking quite well-forward and there may be concerns around keeping the crop standing over winter. However, some winter kill and pigeon feeding can reduce crop biomass over the next few months.
Disease control is now the main focus and although Phoma is present in crops, several varieties have good resistance scores which has helped to prevent early infection in these crops. As a result, there has been little spraying in October. However, the risk of light leaf spot infection increases from November and growers should regularly monitor crops for early signs of this disease.
Leaf samples tested by Bayer’s SpotCheck service in late October has identified light leaf spot across several counties in the East and North, which is not surprising given the wet weather we have had over the past two months.
Pay particular attention to risk-factors in your crop, levels of light leaf spot inoculum from previous crops and the resistance rating of the variety you have used. Any variety with a resistance rating below seven has a higher risk of infection this autumn.
Where growers adopt a one-spray strategy for autumn disease control, using a fungicide such as Proline, with activity against both Phoma and light leaf spot can be an advantage. Keeping the foliage clean for as long as possible will be of benefit come spring, when spore splash in the upper canopy can quickly affect pods.
The early signs of light leaf spot are difficult to identify, so growers can make use of Bayer’s SpotCheck service to test leaves for infection. Results are available within a few days, which can help time protectant fungicide sprays.
It will soon be time for applications of propyzamide for weed control where required, so growers could consider adding a fungicide to the tank mix. Not only can this save additional passes on already wet ground, the risk of light leaf spot infection is greater from November onwards.
The wet weather in October has dampened aphid activity and suction traps have not picked up huge numbers of peach potato aphid. This is good news for oilseed rape crops given the lack of chemical control options now to prevent Turnip Yellows virus.
