South: Countering serious weed concerns

With the exception of crops after maize and those on the worst blackgrass ground, most of our first wheats are safely sown and establishing evenly from good quality seed-beds in a nice open autumn. Our winter barleys are just starting to emerge. And second wheat drilling is well underway.

Some early-drilled wheats without pre-planting glyphosate in the area have actually had to be sprayed-off to deal with rampant blackgrass. So we’re glad we held firm and didn’t start  drilling on farms with particular blackgrass problems until late September.

This enabled us to achieve reasonable stale seed-bed control where it was most needed. Too little soil moisture ahead of many drillings, however, seriously restricted weed emergence. Until the past 10 days, that is, when our first decent spell of rain for a month encouraged low dormancy populations to develop thick and fast.

Although good quality seed-beds with an even depth of drilling have been ideal for the robust pre-emergence herbicide activity that is our second key line of weed defence, dry soils have limited mobilisation. To such an extent that seed-beds filling with weeds were beginning to cause concern.

Thankfully, the weeds are now looking decidedly sick as the extra moisture allows the pre-ems to do the business. This is just as well given the reliance we’re placing on them – not least with our post-emergence options limited by chlortoluron intolerance in the most popular varieties.

Delayed weed emergence, of course, also means generally small blackgrass plants to tackle with the first post-emergence applications we’ll be putting on in the coming week. We’re starting with the low weed risk ground that needed little in the way of a pre-em, and putting special emphasis on tackling high levels of rape volunteers in most crops.

Weed and volunteer control is a key priority for our oilseed rape too. Late cereal harvesting and early dryness meant very limited pre-planting control. And with soil temperatures at 13-14C and little prospect of any rapid cooling, it’s going to be a while before we can effectively apply propyzamide. By which time those blackgrass plants are going to be pretty chunky.

For this reason we haven’t hung around with our first graminicide spray and many crops will need a second spray given the protracted germination of volunteers. It’s certainly good to have clethodim this season. I’ve been impressed by how well it’s working so far.

The dryness has meant slugs have been far less of a problem everywhere. But they’re still there and beginning to be far more active after the recent rain. Knowing how much havoc they can easily wreak, we won’t be breathing a final sigh of relief until the cold weather actually arrives or crops start to tiller.

We’re also keeping our defenses well and truly up on the barley yellow dwarf virus (BYDV) front. With winged aphids easy to find on volunteers and early drillings, we’ll be spraying any non-Deter (clothianidin) treated wheats in the coming week. Even those receiving a Deter dressing are likely to need a spray by early November. And some crops may well need two.

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