The A2 strain causes late blight faster and likes warmer temperatures than the old A1 strain. It also cannot be controlled with the standard fungicide used for almost 15 years. Most troubling for home gardeners, it seems to attack tomatoes almost as often as Irish potatoes. Dry periods during recent springs have kept late blight from being a problem in South Carolina. However, late blight occurs in Florida on winter potatoes and during most summers in all of the major potato-growing areas of the country.
Late blight is found throughout the Midwest on commercial tomatoes.
Fresh market tomatoes in the mountains of North Carolina and in California can also have late blight. To combat late blight, breeders are working with wild relatives of Irish potato and tomato to make new vegetables blight resistant. Chemical companies have designed new fungicides that stop the A2 strain.