South: Phoma continues to spread

Having heard recent reports of high levels of phoma in oilseed rape in the eastern counties, I wondered how long it would take before it reached us – and reach us it has.

Some situations have levels higher than I have ever seen, with 50-60% of plants infected and up to 10 lesions on some leaves. The speed with which it developed in some crops has been alarming.

Prompt action with robust rates of either flusilazole or prothioconazole has been called for, depending on what’s available quickest and whether the fungicide is going on as a tank-mix or not. I tend to find flusilazole a slightly more benevolent mixing partner. Some of these fields, especially those with the smaller plants, will doubtless need re-treating in four to six weeks time.

The winter cereal drilling has generally gone well, with the ground recovering unexpectedly quickly from the 100mm of rainfall two weeks ago. Efficacy of pre- or early post-emergence herbicides has been varied, depending on how emerged the weeds were, the level of moisture at the time of application and the condition of the seed-bed. If blackgrass has survived or recovered I’m coming back in with Atlantis (iodosulfuron + mesosulfuron) now rather than wait for the spring.

Over the years, I’ve found that if you get good control in the autumn there is rarely a major problem in the spring. If brome turns out to be a problem in the fields that have had Atlantis in the autumn, then it could be a lesson in realising that the plough (how dare I mention the word) is not such a heinous devil’s invention after all.

Winter beans are going in as I write and will have a pre-emergence residual accordingly. In the past, I’ve used pendimethalin/clomazone based mixes, but this year I’m trying a bit of prosulfocarb with the pendimethalin (off-label). I’ll let you know how well it’s done next July.

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