South: Timing right for follow-up blackgrass sprays

Oilseed rape crops are romping through the growth stages with some very large canopies present. The warm conditions are suiting the crop rather too well. Even so, I was rather surprised to find DK Cabernet, drilled at the end of the second week in September, already over 30cm tall.

The dry conditions have slowed the spread of phoma significantly. South of Oxford, the disease has now come into the crop and I have applied a fungicide/aphicide mix. But further north, phoma is still absent and I am holding off for the time being. 

Unfortunately, the dry conditions have conspired against decent pre-emergence weed control in cereals. All sorts of problems are evident, some crops have a carpet of blackgrass in them and swathes of volunteer rape, which indicates just how little activity the herbicides have given.

The focus now needs to be on carefully timed follow-up sprays of Atlantis/Horus. In the earliest drilled crops the largest blackgrass is starting to tiller and needs attacking soon. We now have, in this area at least, enough soil moisture for these to work effectively providing the blackgrass is not resistant.

Crops drilled at the end of September and into the first week of October largely went into very dry conditions and although some blackgrass had emerged it is not that large. Now we have moisture more will come through and care will be required with spray timings to avoid missing these later emerging weeds.

Let’s hope the autumn remains open and we don’t get pushed into spring applications yet again. Given the warm conditions and the high numbers of aphids that have been trapped don’t compromise the barley yellow dwarf virus (BYDV) spray timing to coincide with herbicide timings.

Finally, winter bean drilling is in full swing with much of the crop now drilled or ploughed in. Herbicide recommendations have been made and applied. My biggest concern is that in blackgrass and difficult broadleaved weed situations, there is no easy solution and the cost of some of these mixes is horrendous.

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