However, when I grew tomatoes commercially we never had a problem with tomato blight in our greenhouses. But unfortunately we can’t change the weather, so this is not a simple task. So the way to avoid the disease is to avoid the conditions that allow the spores to germinate. Tomato blight spores are wind borne and, as far as I know, there’s no location in the UK where they are unlikely to exist. Especially when fruit or tubers are infested. And this is evident by the watery look of the disease in certain conditions. But technically (here’s the science bit) it is an oomycete or water mould. Thats close enough for us to understand it. It certainly describes the disease well in my view. The name was first suggested in 1876 by the German mycologist Heinrich Anton de Bary. The name Phytophora is indicative of the disease on that in Greek phyto means plant and the remainder of the word “phthora” is Greek for decay, ruin, or perish. In some cases a fine white hyphae like structure can be seen around the lesions, especially on the underside of leaves. What Does Potato Blight Look Like?īlight starts by causing chlorosis of the plant and this is very quickly by brown lesions on leaves and stems. And it is the same blight that caused the Irish Potato Famine. It is now here and has been for many centuries. Where it actually came from years ago is now an academic argument. Flier, indicates that a more likely origin is Mexico. Some report tomato blight as originating in the Andes which is where potatoes originated. Blight surrounds us a lot of the time but only devastates crops when conditions suit it. However, even when spread on the breeze, it will not be problematic unless the Hutton conditions trigger germination. In this way it can be spread miles on a gentle breeze. It should be noted that the main way in which blight is spread is an airborne spore. Spread is more likely as the temperatures warm above 10C and in my experience worse when between 18-25C.

The specific conditions needed to trigger a Hutton Period warning for Blight are temperatures above 10C and relative humidity above 90% for at least 6 hours on two consecutive days. In summer, when the weather has been as it was in 2021, wet and cool, blight is noticeably much worse. Rain often brings cooler weather and hence we get cool moist “Blight” conditions. And this makes it a problem in the UK where the prevailing Atlantic winds are moist and rain a common feature. Tomato Blight Conditionsįor blight to become a problem there needs to be cool moist conditions. Hutton Periods are notified to farmers and growers via the Syngenta website. The conditions is needs to grow and spread have been extensively researched by the James Hutton Insitute (funded by AHDB) and are known as Hutton Criteria. It is not a problem when the temperature is under 10C. Late Blight occurs on both tomatoes and potatoes when certain weather conditions allow it to sporulate, spread and geminate on new plants. It is common in the UK in late summer and should not be confused with early blight which is common in the USA but extremely rare in the UK Early blight is caused by a different organism, and is a form of Altenaria. Tomato blight is caused by a fungi-like organism, Phytophora infestans, and can destroy crops in a few days.