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The cost of potato haulm desiccation without diquat

According to AHDB in the UK, Spotlight and/or Gozai straights or combinations, along with flailing, can give virtually as quick desiccation as diquat. This was shown in trials and demonstrations across AHDB’s Strategic Potato (SPot) Farm network to evaluate potential replacements have shown.

But at what cost?

Dr Mark Stalham, Head of NIAB CUF who led the trials, reveals the results, and Mark Topliff from AHDB’s Farm Economics team crunches the numbers.

The withdrawal of diquat and the absence of like-for-like herbicide replacements available on the UK market poses a real challenge to growers because of its use as a desiccant as well as a herbicide. Potato haulm destruction, which is usually carried out by chemical desiccation, plays a crucial pre-harvest role as it stops the tubers bulking and allows their skins to set. It also reduces the risk of bacteria, fungus and viruses getting in to the crop.

Led by Dr Mark Stalham, new head of NIAB CUF, demonstration plots and experiments designed to help potato growers re-think their desiccation strategies have been taking place in different areas around the country. These include North Lincolnshire-based SPot Farm North, (RJ and AE Godfrey)Elveden Farms (Suffolk), the James Hutton Institute (Dundee, Scotland), SPot West (Heal Farms, Shropshire) and SPot South (Dillington, Somerset).  

Using different varieties, and targeting vigorous, complete canopies at close to commercial defoliation timings, the work evaluated speed of leaf and stem desiccation, skinset, and effects on yields and internal defects on both ware and seed crops.

Two applications at weekly intervals of different combinations of Gozai (pyraflufen-ethyl), Spotlight Plus (carfentrazone-ethyl), Finalsan (pelargonic acid) and Saltex (concentrated brine solution) were made, while one combination of Spotlight/Gozai was applied three times. Actives were also combined with flailing. A hand-simulated haulm puller was applied to the seed experiments.

Assessments were then made at weekly intervals from the first application or defoliation.

The initial results have been assessed from work on the popular ware variety Maris Piper, and the slightly later-maturing Jelly grown for seed.  The maincrop processing variety Royal was assessed at Elveden Farms, the packing variety Georgina at Dillington and the crisper Titan at Heal Farms.

Grow-on after application

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