![]() ![]() In the UK, outbreaks may occur from June onwards, usually earliest in the South West. Whilst it’s possible that tomato or potato material left in an individual garden could act as a source of the disease for the following year, the great majority of infections in gardens arise from wind-blown sporangia originating from other gardens and allotments, and from commercial potato crops. The pathogen overwinters in affected potato tubers left in the ground (and also left by the sides of fields in the case of some commercial crops affected the previous year). Spores produced on the leaves and stems can also be washed down into the soil by heavy rain, and may infect tubers that they come into contact with. Under humid conditions, stalks bearing sporangia grow from freshly killed tissues and the disease can spread rapidly through the crop. ![]() The pathogen then spreads rapidly through the plant tissues, killing the cells. In order for infection to occur prolonged surface wetness (several hours) is required this is why the disease is so serious in wet summers. The late blight pathogen is a microscopic, fungus-like organism whose spores (sporangia) easily break away from infected foliage and may be wind-blown for long distances. There are currently no fungicides available for use by gardeners for use against blight. The latest situation with regard to the dominant strains of blight can be found on the Euroblight website. Visit the British Potato Variety Database for more information. Some old favourites are very susceptible, eg ‘Arran Pilot’, ‘King Edward’, ‘Majestic’, ‘Sharpe’s Express’. These cultivars are not completely immune, so may still develop blight if prolonged favourable conditions for the disease occur, but not to the same extent as susceptible cultivars. There are, however, still cultivars currently thought to show good resistance to the disease, including Athlete, Alouette, Carolus and the Sarpo cultivars (e.g. In the past some potato cultivars had shown limited resistance, these included ‘Cara’, ‘Kondor’, ‘Orla’, ‘Markies’ and ‘Valor’, but this is not currently effective. The genetic population of the blight pathogen is ever-changing and recent research has shown that new strains seem to have overcome the resistance previously exhibited by some cultivars. Operate a rotation to reduce the risk of potential infection from soil-borne resting spores (see ‘Biology’ section, below), ideally of at least four years (also avoid growing tomatoes in the soil during this period)ĭestroy all potatoes left in the soil, and any waste from storage, before the following spring Check any stored tubers regularly for decay Use the tubers from blighted crops as soon as possible, and avoid storing them if at all possible. To prevent slug damage avoid leaving tubers in the soil after this time When the skin on tubers has hardened, after about two weeks, the tubers can be dug up. When infection levels reach about 25 percent of leaves affected or lesions appear on stems cut off the foliage (haulm), severing the stalks near soil level and raking up debris. Picking off leaves or leaflets when just a few are affected may slow down the progress of the disease very slightly, but will not eradicate the problem Gardeners are able to access forecasts of when blight will be active in their region, check if there have been previous instances of favourable weather for the disease, or see if there have been confirmed cases - visit the BlightSpy website, developed for professional growers but providing useful information for gardeners However, early cultivars are still genetically susceptible to the disease, so if weather conditions mean that the disease gets going early in the summer they could still be affected first-early cultivars) are more likely to escape infection, as levels of the disease tend to increase as summer progresses. Infected material should be deeply buried (below the depth of cultivation), consigned to the local council green waste collection or burned, rather than composted (see 'Biology' section, below)Įarthing up potatoes well provides some protection to the tubers from blight spores washed down into the soil from lesions on the leaves or stemsĮarly-harvested potatoes (e.g. Malvern Autumn Show - 22–24 September 2023.RHS Garden Wisley Flower Show - 5–10 September 2023.RHS Garden Rosemoor Flower Show - 18–20 August 2023.RHS Garden Hyde Hall Flower Show - 2–6 August 2023.RHS Flower Show Tatton Park - 19–23 July 2023.RHS Hampton Court Palace Garden Festival - 4–9 July 2023. ![]()
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