South: Countering serious weed concerns - Agrii - Connecting Agri-science with farming

Company News

October 21, 2013

South: Countering serious weed concerns

With the exception of crops after maize and those on the worst black-grass ground, most of our first wheats are safely sown and establishing evenly from good quality seedbeds 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 seedbed 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 seedbeds with an even depth of drilling have been ideal for the robust pre-em activity that is our second key line of weed defence, dry soils have limited mobilisation. To such an extent that seedbeds 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-em options limited by CTU intolerance in the most popular varieties.

Delayed weed emergence, of course, also means generally small black-grass plants to tackle with the first post-ems 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 13-14oC and little prospect of any rapid cooling it’s going to be a while before we can effectively apply propyzamide. By which time those black-grass 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 defences well and truly up on the BYDV front. With winged aphids easy to find on volunteers and early drillings, we’ll be spraying any non-Deter 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.