South: Don’t be complacent with aphid control in cereals

Crops on the South Downs have now established well, with wheat and barley crops growing nicely and generally escaping the slugs. However, wheats after oilseed rape with cloddy seed-beds on clay caps have received ferric phosphate-based slug pellets, to ensure establishment is not impeded by high slug pressure.

Aphid numbers are increasing, but are still below “normal” levels for this time of year.  If weather conditions remain favourable then with no margin for complacency, a lambda-cyhalothrin-based aphicide will be used to stop a secondary spread of aphids and reduce the risk of barley yellow dwarf virus (BYDV), particularly where untreated seed has been drilled. Well timed pre-emergence herbicides based around flufenacet, flurtamone, diflufenican plus prosulfocarb have worked well and are now being followed up with additional flufenacet, picolinafen and pendimethalin where fields have confirmed RRR rated resistance to the likes of Atlantis (iodosulfuron + mesosulfuron).

In oilseed rape, phoma is now becoming more noticeable and many crops are reaching the 10-20% of plants infected threshold for a fungicide treatment. Aphid numbers are also increasing a little, but still at relatively low in rape crops. Slick (difenoconazole) has been used where the primary focus is on phoma and if it proves necessary to come back with a specific light leaf spot treatment later Refinzar (penthiopyrad + picoxystrobin) will be used, which offers a combined phoma/light leaf spot control, with the added benefit of stimulating root development.

Winter beans are generally all drilled now and have received a residual pre-emergence herbicide. Where tank mixes of propyzamide – with the addition of clomazone or pendimethalin, have been applied to warm soils – they will have a relatively short effective period and so carbetamide will be used as a ‘top-up’ post-emergence herbicide where required.

This autumn, cover crops have not produced the levels of biomass seen in previous years and while there are many reasons for this, it does raise questions. Perhaps just having something permanently growing in the soil and complete soil cover is all we really need? Is it necessary to chase big yields of biomass? As the nights rapidly draw in, this is something for me to ponder and research further.

Longer term and well developed no-till systems have this year shown that, under favourable conditions, there has been little variation in crop establishment attributable to the type of no-till drill employed and most have produced excellent results. I suspect that this is in no small part due to a gradual improvement in soil biology and organic matter levels.

See more