Article taken from Farmers Guide, September 2017.
Oilseed rape growers have a new early post-emergence weapon this season to control a range of problem broad-leaved weeds.
Parish contains 320g/litre of phenmedipham, an active ingredient that until now has been restricted to sugar beet and related crops in the arable sector.
It can be applied on its own at 1. 1-litres/ha, or with the adjuvant Nelson, which improves efficacy, at half rate, reducing costs.
Under the right conditions Parish will control chickweed, poppy, groundsel, field speedwell, cranesbill, red dead-nettle and shepherd's purse.
It must be applied when weeds are between cotyledon stage and two leaves unfolded and in bright sunny conditions when weeds are growing well. A water volume of 200-250-litres/ha applied through a medium spray is recinnebded to ensure good coverage.
Parish will be a useful addition where growers are reluctant to use pre-emergence protection, for example where flea beetle is a major problem, preferring to ensure adequate establishment before spending their money.
It also looks a good option where seed has been broadcast and pre-ems cannot be used, or to top up poor pre-em control.
It is also a useful pre-cursor to Clearfield herbicides where cranesbill is a problem.
PGR thoughts
We Will soon need to think about plant growth regulation in forward oilseed rape crops. As a rule of thumb, crops that exceed 25cm in height by mid to end of September should be treated, to reduce top growth and encourage root growth. This improves the crop's overwintering capacity and helps promote strong early growth in the spring.
I'll be recommending Caryx at 0.5-litres/ha in leafier crops - it contains the specific growth regulator mepiquat as well as metconazole. Sunorg Pro, which contains metconazole only, but more of it, is a good option in less growy crops, applied at 1 00ml/ha per leaf stage, which also offers some early preventative disease control.
Black-grass is now rife in this area and Avadex (tri-allate) is routine on many farms to complement the pre-emergence stack.
Most growers have access to an Avadex applicator, so will use the granular form. It is worth getting the applicator tested to ensure it is spreading correctly. Forward speed should not exceed 8kph to maintain accuracy of application.
The launch of a new liquid formulation of Avadex is good news for growers who don't have access to an applicator. This is often where black-grass is less troublesome, although any black-grass present is likely to be herbicide resistant, having been introduced from problem areas.
I would recommend including Avadex as part of a zero-tolerance policy. Although the liquid formulation puts down slightly less active ingredient than the granules, to meet operator safety requirements, it will still be a very useful addition to the armoury.
In all cases my pre-emergence stack will consist of Trooper (flufenacet + pendimethalin), plus Herold, which also contains flufenacet and adds diflufenican.
I'll also add Remix as routine. This is a long-chain paraffinic oil that reduces spray drift, improves spray deposition and increases adsorption to soil particles.
That improves weed control and crop safety.
In trials over the past few years, Remix has consistently added an extra few percentage points of control that can make the difference between reducing the seed return, or allowing it to increase.
Esme Shephard is an agronomist with Agrovista, based in Wiltshire (esme.shepard@agrovista.co.uk)