YOUR QUESTIONS ANSWERED
Beating blight, failing rhubarb and cockatoo plants
QMy neighbours on either side have lost all of their outdoors tomatoes to blight. They both removed most of the leaves from the plants. Another neighbour two doors along, has, so far, not had any blight. Our greenhouse tomatoes have shown signs of blight or something similar. Why is this?
Andy McIlvenna and neighbours
AIt is very bad luck for your neighbours to have lost their tomatoes so quickly to blight.
Let me tell you a little about the disease and see if that helps you all to know what to do in the future.
The fungus that causes blight is encouraged by warm wet weather and its spores are spread by air currents and water splash.
A film of moisture covering the leaves is necessary for the spores to take hold and infect the plant, so anything that can be done to prevent moisture sitting on the foliage will help, such as watering the ground directly and keeping air moving around the plants.
For greenhouse plants keep doors and vents open as much as possible to encourage air movement to reduce condensation.
If you grow tomatoes in the greenhouse every year it is worth disinfecting the structure and glass during the winter to be sure of dealing with any spores. Jeyes Fluid is very effective.
Use fresh growbags or compost each year, or sterilise the soil if planted in beds. Greenhouse tomatoes are less vulnerable to blight being in an enclosed environment, but they are not entirely safe from infection. Unfortunately there is little you can do to prevent the fungal spores being released (they can travel quite some distance on air currents) so it is worthwhile considering doing some preventative spraying.
This should be done as soon as the first tomatoes have set, and then repeated according to the manufacturer’s instructions. A copper-based fungicide is ideal. There is little you can do once the disease has appeared, but it might be possible to slow the spread by removing infected leaves as soon as they are spotted. However, it is a fine balance and if too many leaves are removed the plant has no means of photosynthesising or drawing water up and therefore no means of providing nutrients or water to stems or developing fruits.
This will effectively mean the death of the plant anyway.