There are now, however, tomatoes with genetic resistance to late blight. Resistant Varieties The wild tomato Solanum pimpinellifolium was one of those used in developing new resistant tomatoes. Worse, just when the fruit is almost ripe, soft brown or black depressions form on it and it begins to rot. The disease rises successively upwards, affecting leaf after leaf. White cottony growths may appear under the affected leaves … if the air is humid. At first, brown marks appear on the lower leaves and grow quickly in size. Notably, it shows up in late summer (it’s not called “late blight” for nothing!). You can recognize late blight by its symptoms. In fact, in climates with fairly humid summers, where late blight is most prevalent, late blight of the tomato is now that plant’s most devastating disease. But the new strains that appeared, notably US-22 and US-23, are much more virulent than the older ones and particularly harmful to tomatoes. This is an old disease, the one that caused the Irish potato famine in the late 1840s (the same disease also attacks potatoes), and gardeners thought that the disease was pretty much under control, since most commonly grown potato and tomato varieties of the time had some resistance to the original strains. New strains of tomato late blight ( Phytophthora infestans) appeared out of Mexico, homeland of the tomato, in the late 1990s and, by 2010, had spread all over the world, taking both seed suppliers and gardeners by surprise. Tomatoes showing tell-tale symptoms of late blight.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |