Pre-emergence herbicide strategy


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Insights to help growers develop a cost-effective weed control strategy

KNOWING your field, including soil type, layout and topography, as well as previous cropping and current weed burden, is the keystone to staying ahead of the game by devising a made-to-measure herbicide strategy, according to Andrew Goodinson, who has been working for Hutchinsons for 16 years and looks after nearly 8000 ha of farmland, ranging from Cirencester, to the Welsh borders, south Shropshire and Worcester.  

One of the challenges many growers face is that they are growing on rented land, so the knowledge of the previous history of the field can be limited, so he likes to walk the field, inspect stubbles and map out and identify patches of weeds, identifying control priorities.
Andrew said: “There are a wide range of soil types and weed spectrums, and as you cultivate you can bring up buried weed seeds, some of which can be more of a threat than others.

 “Weeds such as bindweed and cleavers can grow though the crop and smother the canopy, while others, such as fat hen, oilseed rape, and thistles also compete with the crop for nutrients, light and water.

“Those of a similar family to the crop, such as cleavers and black nightshade (Solanum nigrum), not only compete, but they can also host pests such as Rhizoctonia which can hit quality and yields.” 

Black nightshade, which is prevalent where Andrew is based in the west, is one of his ‘priority weeds’. According to the AHDB, seeds can remain viable in the soil for over five years, and may also eaten by cattle when grazing, so seeds are then passed out and applied back onto the field. 

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“Fortunately, we have still some useful tools, such as Defy (prosulfocarb), Artist (flufenacet) and Inigo (metobromuron), which help keep on top of black nightshade control, although it is an area of weakness for aclonifen.

Fat hen is another priority weed, as it has a high number of seeds and grows rapidly and can cause shading of young crop plants. “One of the problems of this weed, which likes high nitrogen loams and sandy soils, is not only does it compete for nutrients but it can also grow higher than the spray boom, and can affect blight spray efficacy. It can also create a micro-climate where blight spores can proliferate.” 

In areas where fat hen is prevalent, Andrew recommends aiming for pre-emergence control, and then if the weed is present at the time of spraying, using protoporphyrinogen oxidase (PPO) inhibiting herbicides as part of a tank mix to remove any which have emerged. 

Other weeds high on Andrew’s priority list include black bindweed, cleavers, fumitory and thistle.

To read our fuller feature, see the March issue of Potato Review. You can subscribe here.

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