Suffolk-based Ella Crawford offers advice on keeping the number one oilseed rape disease at bay and maintaining good grass-weed control in wheat crops this month
This month’s update includes information on:
In Suffolk, milder and wetter weather in January has put spring crop preparations on hold and the recent drop in temperature has also slowed any winter crop growth.
There was some forward oilseed rape crops pre-Christmas, which the cold and frosty weather has helped knock back. It’s also checked aphid and cabbage stem flea beetle larvae activity and may have slowed disease progression.
Cabbage stem flea beetle larvae
Results from SpotCheck samples sent in to ADAS have uncovered latent light leaf spot infection in susceptible varieties, driven by wet weather in January. We would expect to see some of that latent infection develop into visible lesions in the coming weeks and growers should continue to monitor for signs of the disease – particularly early drilled crops.
There is no threshold for treatment pre-stem extension, so as soon as its seen, a light leaf spot-active fungicide such as Proline (prothioconazole) at 0.32l/ha should be applied at the earliest opportunity.
While it is tempting to hold off and combine light leaf spot control and PGR activity in one spray, this can allow light leaf spot to become established and harder to control. Where disease does become established, the Proline rate can be increased to 0.46l/ha. Any Proline application will also top up phoma control and reduce stem canker development later in the season.
Growth stages in wheat range from those just emerging behind roots to the most advanced at GS26. The most advanced winter barley crops also have up to six tillers.
Despite the colder conditions, septoria and mildew are evident on older leaves of wheat crops, however recent frosts have knocked back rusts in places. Fungicide application isn’t usually required before the T0 timing in March, but disease progression is something to keep an eye on. It is a good time to make a note of current disease levels and plan for the T0 timing based on risk factors such as variety and drill date.
Barley is slightly different in that there is more emphasis on disease control earlier in crop development, with tiller survival crucial for final yield. It is a good idea to monitor for mildew, rusts and net blotch and treat with a T0 fungicide where pressure is high to maintain tillers numbers.
In Suffolk, growers didn’t shy away from heavy stacks of autumn residual herbicides in wheat and the longer half-life of actives such as flufenacet and DFF has meant overall, grass-weed control has been good. Any remaining black-grass and rye-grass is still small.
Growers should monitor the black-grass left behind and if a post-emergence herbicide wasn’t applied pre-Christmas, an application will be required as soon as the temperatures pick up and there is active weed growth.
Black-grass
There are a range of options, including Atlantis (iodosulfuron + mesosulfuron), Pacifica (iodosulfuron + mesosulfuron) and Monolith (mesosulfuron + propoxycarbazone). Choice will depend on your target weed. For black-grass and other grassweeds, Monolith will be the best choice, as it will give on average 10% extra control of black-grass over Atlantis WG. For situations where broad-leaved weeds are a problem, Atlantis or Pacifica are preferred options, as they have more tank-mix flexibility when adding in other broad-leaved weed herbicide partners.
The sugar beet crop is about three-quarters lifted and yields have continued at record-breaking levels throughout the campaign, with 100t/ha not uncommon. Sugar content has also been good, averaging 17.8%. Those that used a third fungicide to control the late rust and cercospora epidemic have certainly seen a benefit this year.