If you gardened last year, you know we had a devastating late blight outbreak. I don't know of anyone who had tomatoes make it through the entire growing season.
Luckily, the strain of late blight we had in 2009 needs living tissue to overwinter. It will not be in your seeds or in your soil. The only way late blight can and may have overwintered in our area is on potatoes, since the tuber is still living plant material. There are some steps we can take to help reduce the risk of another late blight epidemic.
Let's start with tomatoes. Try to select disease-resistant varieties for at least some of your crop. "Mountain Magic," "Plum Regal," and "Legend" are three varieties with resistance or tolerance to late blight. Because they are new to the market and of last year's epidemic, it is impossible to find seed for these resistant varieties. Growing your own transplants or purchasing from a reputable grower will ensure a healthy start to the season. Inspect all transplants you buy for cankers or leaf blight before planting. If the plant does not look healthy, don't buy it.
As for potatoes, do not save tubers as seed to be planted next spring. Purchase certified disease-free potato seed from a reputable source, and ask your supplier if the field was inspected for late blight. In the spring (April - June), inspect last year's potato plot and any compost or cull piles for volunteer potato plants that might come up. If you find potato plants, pull them out and put them in the trash or destroy them. If tubers were infected and survive, then the late blight could grow upward from the tuber, infecting the stem and producing spores when weather conditions are favorable. These spores could then create another epidemic.
For both crops, provide good soil fertility, water drainage, air circulation, and use cultural practices to provide what the crop needs for healthy growth. And finally, during the growing season, pay attention to weather conditions and pest alerts to learn about whether late blight has been observed in New York, and what actions you need to take to protect your crop.
Anne Lenox Barlow is the horticulture educator with Cornell Cooperative Extension in Clinton County. CCE offices may be reached in Clinton County at 561-7450; Essex County, 962-4810; and Franklin County, 483-7403. E-mail your questions to askMG@cornell.edu.