Potato Review

44 POTATO REVIEW SEPTEMBER/OCTOBER 2019 M uch progress has been made in the area of potato seed health over recent decades, with seed producers now more knowledgeable and professional than ever before. However, more can be done, and the experts are urging growers to sharpen up production practices – particularly store hygiene – to reduce levels of fungal pathogens on seed and its subsequent progeny. In this feature, we review some of the pitfalls and best practice. Constant threat Despite issues such as silver scurf, dry rot, gangrene and skin spot, which can develop and cause problems in store, often being season speci c, SAC Consulting seed production expert Innes Jessiman says risk from all four is always lurking in the background. As a result, growers should remain vigilant year on year, be aware of the conditions that favour each pathogen and address any potential sources of infection for fresh tubers heading into store. An integrated strategy to minimise the spread of inoculum and development of disease symptoms can then be planned for the season ahead. e main area where Mr Jessiman believes the seed industry can up its game is store hygiene, which makes a considerable di erence to the nal disease levels of a seed crop when loaded out of store. e window between old crop going out and a new crop coming in should be utilised to thoroughly clean stores and grading areas, removing any soil and dust with a vacuum cleaner. One of the main sources of infection in stores is dust carrying fungal spores, which is kicked up by forklifts and other machinery, eventually settling on clean tubers coming in from the eld or grading shed. Mr Jessiman adds that where possible, buildings should also be power washed, preferably with a disinfectant such as peroxyacetic acid ( for example, Jet 5) to kill any remaining spores. Fogging stores with peroxyacetic acid, typically carried out by a contractor, is also an option and although more expensive, is highly cost e ective, having been shown to kill up to 90% of fungal spores after treatment. Nick Green, Director of Lincolnshire-based Stored Crop Conservation and Chairman of the National Association of Agricultural Contractors (NAAC) CIPC application group, whose members also specialise in store hygiene, says fogging costs about 40p/tonne and has become popular amongst top seed and ware producers. For maximum e cacy, pre-cleaning of stores must be thorough, with all dirt and dust vacuumed and washed from oors and building fabric, enabling fog to hit every surface. With the vast majority of seed producers harvesting straight into boxes, these can also provide a source of inoculum for the new crop and can be stacked in store during fogging for a “free” disinfection. If not fogged, the dirtiest boxes should also be power washed, while cleaner boxes can be left outside for UV light to kill any resting fungal spores. Mr Green stresses that peroxyacetic acid is contact-acting and has residual activity, so fogging should be carried out as close to store loading as possible. “Hygiene and cleanliness around stores and in adjacent buildings such as grading sheds is also important, as forklifts or wind can pick up dust and recontaminate clean buildings,” he said. An integrated strategy to minimise the spread of inoculum and development of disease symptoms should be planned for the season ahead. Seed health Growers given a timely call to raise their hygiene game to ensure healthier seed. SEED HEALTH