IN THE FIELD Richard Overthrow


Newly drilled crops require care this autumn


A catchy harvest led to a catchy drilling season but at least that suggests some consistency, writes Richard Overthrow


H


opefully, most of the autumn crops are in now with only winter beans and late sown


wheat, due to grass weed pres- sure or late harvested root crops, left to go in. Remember to adjust seed rates for these late cereal sowings, particularly if delaying due to grass weeds. This approach only works if the crop is competitive from the off so needs to establish and cov- er the ground fairly promptly. Oc- tober sowing increases the likeli- hood of rainfall and hence moist seedbeds to get the best out of re- sidual herbicides, another advan- tage in delayed sowing. Growers without grass weed problems should still aim for au- tumn treatment of broadleaved weeds because treating when tar- get plants are small will make herbicides more effective and al- low growers to reduce doses. Slug monitoring should con-


tinue, as many cereal crops start to emerge. Remember to follow stewardship guidelines, particu- larly if using metaldehyde. Ferric phosphate products are as effec- tive as metaldehyde and should be considered particularly where there is a risk of run-off or other means of water contamination should metaldehyde be used.


14 MIDLAND FARMER • OCTOBER 2017


Aphid activity BYDV control programmes will be ongoing, protection is needed until the end of aphid activity, typ- ically in early November. Make sure insecticide protection cov- ers the crop until that point. De- ter seed treatments can protect the crop for up to six weeks after drilling but if this doesn’t cover the whole risk period then follow- up sprays will be needed. However, recent mild autumns showed us that protection may be needed well after the end of the flight period, even if aphids have stopped flying-in. If such condi- tions return this autumn then a more robust approach to insec- ticide protection will be needed. In oilseed rape, cabbage stem flea beetle numbers were varia- ble this year but quite serious in some areas: next comes the lar- va problem, which doesn’t seem to relate to adult numbers any- way. There are no control options against the larvae unfortunate- ly and the only option is to leave alone and hope the crop comes through any infestation. Rape crops should also be monitored regularly for the ar- rival of the first phoma lesions. First sprays should be applied


when the threshold is reached (one plant infected in ten, or one in five for resistant varieties). If sprays need to be applied at the start of this month then a follow-up is likely to be needed if new lesions arrive later in au- tumn. If the first spray isn’t ap- plied until the end of this month then it will likely protect the crop for the infection risk period, and should cover as an autumn treat- ment for light leaf spot.


Cereal volunteers


Early cereal volunteer sprays will have been applied to young rape crops but second gramini- cide sprays for grass weeds may be applied this month. Remem- ber if two ACC-ase graminicides are applied to a crop, they must be different active ingredients targeting different weed species. Carbetamide and propyz- amide are popular post-emer- gence residual herbicides. Both need soil temperatures to fall to certain levels before they are ap- plied, though recent trials have shown that a sequence of the two can be effective against difficult black-grass populations. Applying carbetamide in the early part of this month with pro-


TIMELY TIPS


• Treat broadleaved weeds while small


• Monitor rape for first phoma lesions


• Apply second graminicides to grass weeds


• Sow winter bean from middle of month


pyzamide at its more tradition- al later timing would be particu- larly useful where there is known to be significant resistance to fo- liar graminicides (ACC-ase in- hibitors). Winter bean crops can be sown from the middle of this month. Early sowing should be restrict- ed to the shorter varieties as the crop responds quite markedly to sowing date in terms of final crop height and therefore lodging risk.


› Richard Overthrow is a region- al agronomist with NIAB TAG, the UK’s largest independent agrono- my organisation with several re- search centres. For more details call 01223 342495.


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Slug monitoring should continue as cereal crops start to emerge


Light leaf spot and phoma on oilseed rape


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