Oilseed Rape

OSR crop report – February 2023

Oilseed rape are generally looking good at the end of January. Some are more forward than desirable for this time of year, although recent hard frosts have knocked them back a bit.

Freezing temperatures have also held back Cabbage Stem Flea Beetle (CSFB) larvae feeding so far, but crops will need to be monitored into the spring. Areas that have not experienced the freezing conditions are finding CSFB larvae more prevalent in plant petioles.

Around 60% of crops received an autumn fungicide before the end of 2022, but Light leaf spot is being seen on the older leaves of nearly all crops, and is especially prevalent in varieties with a resistance scores of six or below.

As we move towards spring, warmer, wetter weather will increase the threat of light leaf spot infection and spread, so all crops should be monitored regularly. The early stages of light leaf spot look like small grains of sugar on either side of the leaf. They can be sporadic across a field and are difficult to identify. The disease can also be present in the leaves without showing physical symptoms.

Bayer’s SpotCheck service can help to identify latent disease in the leaves, and where signs on the leaves are unclear.

Crops which did not receive an autumn fungicide application should be checked regularly, and a fungicide applied at the first signs of disease. AviatorXpro provides robust control of light leaf spot, with two actives, alongside other physiological benefits.

Where an autumn fungicide was applied, the approach will be driven by the active used. If a prothioconazole such as Proline was used alone or in conjunction with tebuconazole in the autumn, growers can choose to apply Proline again, or switch to AviatorXpro for more robust protection in the spring. However, if AviatorXpro or another SDHI was used in the autumn, Proline should be used in the spring.

Priorities now:

• Assess crop condition coming out of winter

• Monitor crops regular for signs of light leaf spot and use SpotCheck to confirm

• Apply a robust spring fungicide if disease is identified

OSR crop report – March 2023

In general, oilseed rape crops are looking good coming out of winter, and decisions can be made on whether any backwards crops will be taken to harvest, or not. Across the UK, crops in the north are generally looking better than those in the south, and east, where dry conditions hampered establishment or were hit hard by cabbage stem flea beetle.

Disease levels remain quite low, with only a few positive SpotCheck tests for light leaf spot. Infections on the lower leaves are less of a concern as these will drop off as the crop goes away.

However, as temperatures increase, disease levels are expected to rise, so regular field walking and monitoring for light leaf spot will be increasingly important. At this time of year disease can move rapidly up the plant through rain splash and coincides with rapid growth and stem extension in the crop.

Any autumn-applied fungicides will have run out of steam by now, so spring fungicide applications will likely be required in March. Pay particular attention to crops that did not receive an autumn fungicide, and varieties with resistance scores of six or below.

Fungicides only provide protectant activity, so apply in advance of seeing light leaf spot infection in the crop, or at the first sign of disease. Where disease has not yet been identified, Proline plus tebuconazole will provide good protection.

Where disease is present in the crop, and providing a SDHI fungicide was not used in the autumn, an application of AviatorXpro will provide robust protection as well as offer some beneficial physiological effects to the crop.

Choose a robust fungicide that specifically targets light leaf spot. If an SDHI fungicide was used in the autumn, a straight prothioconazole such as Proline provides good protection. Tebuconazole can also be a useful fungicide at this time of year, especially if some growth regulation of the crop is required, and can be applied alongside Proline in tank mix.

If a SDHI has not already been used in the crop, AviatorXpro provides a robust alternative with two actives for enhanced control of light leaf spot, along with other physiological benefits.

Whichever fungicide is chosen, spray operators should ensure they use sufficient water volume to achieve good coverage and penetrate a fast-growing canopy.

Growth regulators may be required on early-drilled and more-forward crops, especially those drilled in August last year. These crops are also likely to need trace elements in March, particularly Boron and Molybdenum.

Priorities now:

• Monitor crops for signs of light leaf spot and use SpotCheck to confirm disease presence

• Apply a robust spring fungicide if disease is identified

• Apply trace elements and growth regulators if required

OSR crop report – April 2023

Crops in the north were looking in good shape at the end of March, but some southern crops have been impacted by Winter stem weevil feeding as well as Cabbage stem flea beetle. Affected crops may recover, depending on the level of damage, but will be thinner and this will reduce yield.

Phoma and Light leaf spot diseases are increasingly present in crops, with Light leaf spot lesions moving up the canopy as stems extend. Crops will start to come into flower during April, but the colder weather in March means the flowering period may be extended this year, with a corresponding extended risk period for Sclerotinia. Crops damaged by Cabbage stem flea beetle or Winter stem weevil may also experience delayed flowering.

The priority in April will be to apply a fungicide to protect against Sclerotinia.

If opting for a two-spray strategy this spring, AviatorXpro is a robust dual-active fungicide which will protect against Sclerotinia infection alongside Light leaf spot and should be applied as soon as crops start to come into flower and sprayers can travel.

A second application of straight prothioconazole such as Proline can then be made towards the end of April or into May if required, depending on the length of the flowering period, and to provide maximum yield protection.

A crop can only receive a maximum of two SDHI fungicide sprays, so product choice may also depend on what autumn applications were made.

April is also the final opportunity to remove any remaining broad-leaved weeds in the crop, but any herbicides must be applied before flower buds are visible to avoid damage.

Priorities now:

• Monitor crops for signs of flowering

• Complete broad-leaf weed control before flower buds appear

• At flowering, apply a robust fungicide to protect against Sclerotinia and Light leaf spot

OSR crop report – May 2023

By the end of April most crops were in flower and looking well, including filling any gaps created over the winter. Those crops hit by stem weevil larva and took a hit earlier in the year, are now growing away.

After a mixed-bag of weather in April that delayed some spray applications, growers can now get back on track and ensure fungicides are applied to protect against Sclerotinia at flowering.

Early flowering crops that have already received a fungicide application may require a top-up during May, especially if showery weather continues. AviatorXpro provides excellent protection against Sclerotinia as well as offering the crop some physiological benefits. However, if the crop has already received two SDHI fungicides, an application of Proline (prothioconazole) is a good alternative.

Later-flowering crops will likely receive just one fungicide application, and a robust fungicide should be chosen, such as AviatorXpro.

This is a good time of year to assess variety choice, reviewing the performance of crops in the ground and those harvested last year. Consider disease and virus resistance and discuss the options available from Dekalb with your local Bayer Commercial Technical Manager.

Priorities now:

• Complete fungicide applications against Sclerotinia

• Monitor crops for disease spread and consider whether second applications are required

• Review variety performance and options for next season

What’s happening in oilseed rape in June

At the end of May crops are looking good and those in the south are coming to the end of flowering with good potential, however many crops are around 10 days behind previous years. Most crops only received one fungicide spray during flowering as the cooler, mainly dry weather during May supressed the risk of Sclerotinia.

June activity will mainly be focused on seed maturity and deciding when to desiccate. They key to maintaining yield at desiccation is to be guided by the crop, and not spray to a pre-determined calendar date. Spraying too early will result in loss of yield, but leaving it too late can increase the risk of pod shatter.

Dekalb varieties, and some other hybrids with in-built pod shatter resistance, provide a degree of flexibility in the timing of desiccation sprays and help to prevent some seed shedding in wind and hail.

To test seed maturity, walk into fields and take pods from across the crop, don’t just sample from the edges. Ideally, sample 20 pods from areas of the crop that hold most of the yield. Look for a change in seed colour from green to brown. When around 30% of seeds have matured, desiccation can be carried out providing crop moisture is below 30%.

Apply a good quality glyphosate formulation, such as products in the Roundup range which also have low-drift qualities, paying attention to spray quality for optimum coverage and canopy penetration. In thicker crops, water volumes of 200 – 250L/ha will help aid effective desiccation.

When considering optimal spray windows, remember that the harvest interval is 14 days. Any crops grown for seed cannot be sprayed with glyphosate.

Looking forward, it’s a good time to review variety performance and make decisions for next season. Have a chat with your local Commercial Technical Manager about Dekalb’s range of hybrids at Bayer’s upcoming Field Days taking place across the UK in June, including oilseed rape demo plots at Callow on 29^th June.

Priorities now:

• Walk fields and take pod samples to check seed maturity

• Apply glyphosate to desiccate crops

• Review variety performance and options for next season