Potato Review

24 POTATO REVIEW MAY/JUNE 2020 MOLLUSCICIDES H ISTORICALLY, growers have been slow to take up the use of ferric phosphate as a slug control solution in the UK, and with the ban of metaldehyde now overturned, those already using products containing this compound could well be tempted to stick with what they’re used to. Slugs respond di erently to ingesting ferric phosphate and the results are less ‘visible’ owing to the fact that there are fewer dead bodies above ground. So what are the advantages o ered by ferric phosphate products and how does it stand up against metaldehyde? De Sangosse, a French company that has spent more than 40 years developing and manufacturing slug baits and biocontrol products for the UK market, recently opened the doors to one of its research and development labs, in Agen, France, to give Potato Review an insight into some of the work it carries out and why it believes ferric phosphate is a show of strength in the ght against one of the most widespread and damaging pests in potato crops – the grey eld slug Deoceras sp. is pest’s activity, survival and reproduction are dependent on moisture and they are more abundant in heavy soils with high clay or silt content. Crop residues and weeds can provide the slugs with a source of food and shelter. Slug damage is considered as a major/ critical defect by the main UK supermarkets No more grey areas Stephanie Cornwall gets a behind-the-scenes look at a French company’s studies into stamping out grey eld slug issues – and a secret anti-leeching recipe. and food processors and can lead to product rejections. Typically, fresh potato packers and processors will reject grower deliveries into their factories with a slug damage threshold of 2 - 5%, according to Jon Williams, De Sangosse Technical Manager. Slug feeding damage can be deep into the tuber and therefore wouldn’t get past the three peel limit, for complete damage removal, on a standard potato peeler test at customer QC intake testing. Where higher slug damage levels are seen, the price could easily be reduced by 50%, potentially a £6K Ha loss to the grower. In 2014, research showed that the grey eld slugs caused direct losses of £53m in potatoes in the UK. Jon said: “At the end of the day, you can’t hide slug damage. e worst consequence to a potato grower is that if the slug damage is over the acceptable damage level, the factory which holds the contract to take his produce, may reject the whole lorry load outright and say ‘take it away’ and will also be within their rights, to also reject anything else from that same eld . However, in most situations, both parties come to an agreement and the load is accepted but with a reduced payment.” Slugs are most damaging at the early stages of tuber bulking. ey enter through small holes in the skin, causing irregular-shaped holes on the tuber surface, extending into large cavities inside the tuber. ➜ Slug damage Wireworm damage