![]() The genetic population of the blight pathogen is ever-changing, so it is possible that new genetic strains could arise at any time that may overcome the resistance previously exhibited by some cultivars. Greenhouse-grown tomato crops are less likely to be affected, simply because the wind-blown blight spores are less likely to reach the plants, but if spores do blow in through the door or vents then the disease can be just as damaging. For example, the cultivars 'Crimson Crush' and 'Mountain Magic' performed very well at Wisley in 2021, when blight was extremely widespread and susceptible cultivars were severely affected. However, they may still give a good yield when susceptible cultivars would succumb completely to the disease, and are particularly useful if the cultivar is one that is suitable for outdoor crops. Many tomato cultivars are very susceptible, but cultivars are now available for most types of tomato that claim resistance to the disease (see seed catalogues or packets for details). Even these cultivars are not usually completely immune, and will probably succumb to the disease to at least some extent if prolonged favourable weather occurs. Operate a rotation to reduce the risk of potential infection from resting spores in outdoor soil-grown tomato crops, ideally of at least four years (also avoid growing potatoes in the soil during this period).The soil or compost could be distributed over an area of the garden not used for growing tomatoes or potatoes. Re-using soil or compost will also increase the risk from a range of other diseases that can attack the root system or the vascular system of the plants. Due to the potential risk of long-lived resting spores being produced by the blight pathogen (see the ‘Biology’ section, below) it is best not to use the soil or compost from a blight-affected greenhouse crop to grow tomatoes in the following year.Attempting to harvest and ripen green fruit from affected plants indoors may therefore result in a large percentage of the fruit subsequently rotting, so using the unripe fruit immediately (for example to make chutney or sauces) may be a better option ![]() Once a plant has developed high levels of the disease on the leaves and stems it is likely that many of the fruit will also have been infected, even if they don’t yet show symptoms. Use the fruit from affected crops as soon as possible.Ensure that the foliage of greenhouse-grown tomatoes is kept as dry as possible. ![]() Picking off leaves when just a few are affected may slow down the progress of the disease very slightly, but will not eradicate the problem.This has been developed for professional growers of potato crops, but can also provide useful information for gardeners growing tomatoes as well as potatoes ![]()
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