East: Grassweed herbicides a priority in brighter weather

The last month or so has been a frustrating non-starter, with the only real field work being nitrogen applications. However, it finally feels as though spring has sprung and with a good forecast for this week we can finally catch up on some field work.

The early nitrogen applications are now starting to show in the crops as they green up and put on new growth. Any outstanding fertiliser requirements should be a priority to apply.

The next main focus is grassweed herbicides that will have been going on this week with the warmer, drier weather. Ideally they will be applied alone, but where rust is an issue or workload dictates, Rubric (epoxiconazole) may be included in some cases.

Due to the mild winter, grassweeds have continued to grow and we need to be realistic about the blackgrass population and level of control possible. In some cases we have taken the view to sacrifice areas of fields. With commodity prices where they are this is perhaps the year to do something different and try and get on top of the problem.

Oilseed rape crops range from being well into stem extension through to stalks at ground level, but most are now growing away from pigeons. Cabbage stem flea beetle larvae can be found easily in leaf petioles and some are now in the stem – perhaps to a greater extent in the earlier drilled, better looking crops that did not require the same level of autumn insecticide. On the plus side, these crops are bigger and stronger and hopefully able to withstand the damage. The most forward crops have received a high rate of tebuconazole for light leaf spot and to give some degree of growth regulation and this will be followed up at green/yellow bud.

Winter barley has now started to pick up the first nitrogen dose. There is plenty of mildew and rhynchosporium present in crops and most will receive a low cost T0 to reduce disease pressure and help maintain healthy tillers, also applying a plant growth regulator and trace elements. The second dose of nitrogen will follow around GS30 to maintain crop development, tiller numbers and maximise grains per ear.

Some of the early cereal crops are slowly approaching growth stage 30 and it is now crucial to monitor growth stage and ensure fungicides are applied at the correct time, as crops that look the most forward aren’t always the most advanced. T0 should be timed around GS30, when the distance from the base of the plant to the ear on the main stem is 1cm or more, but the internode is less than 1cm. If we go too early then an additional fungicide will be required to ensure intervals are not stretched beyond 3-4 weeks, although disease pressure is likely to dictate timing to some extent.

With the level of septoria in fields, a multisite in Bravo (chlorothalonil) at T0 will be essential to protect new growth and create a fire break to disease moving up the plant. Yellow and perhaps more concerning brown rust can also be found in fields and depending on variety and field situation, a strobilurin or triazole will also be included.

When considering fungicide inputs then location, variety and weather conditions will ultimately dictate the level of input required. The first two important areas we know are location and variety and by reviewing previous treated and untreated data, we can see where the focus needs to be. Solstice in 2014 gave a 5.42t/ha yield response to a full fungicide programme compared to Skyfall at 2.55t/ha. In 2015, Solstice gave a 3.42t/ha yield response and Skyfall a 1.69t/ha. This highlights the genetic difference in the varieties and although we can’t be complacent with the more resistant varieties it certainly helps us to tailor inputs accordingly by variety, depending on weather conditions.

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