I can still hear the old farmer grunt, “In a dry season you’ll lose yer crop, in a wet season you’ll lose yer farm”. Actually that was my vegetable crops professor at the University of Massachusetts. He was just trying to get the point across that water can turn from ally to enemy very quickly — this is more evident with tomatoes than any other crop you might try in the garden. More rain means more disease on tomatoes. As a rule in the northeastern US, tomatoes will develop diseases such as Early Blight, Anthracnose, and Septoria when conditions are excessively wet. In your gardens at home there are some simple steps that you can take to help prevent or at least delay the onset of tomato diseases. Even If you don’t have a greenhouse or high-tunnel, the following three steps will help to fend off these annoying diseases and extend your tomato harvest well into September.
Avoid overhead watering. Rain is hard enough to deal with when growing tomatoes. Don’t compound the problem with overhead sprinklers. You’ll use less water, and water more effectively, with a soaker hose or drip irrigation kit (easily found on Amazon.com or at your local garden retailer). Water before noon whenever possible to avoid going into the night with wet conditions in the garden.
Grow up or upside down. Keeping your plants off of the ground will promote air movement through the foliage, reducing the amount of surface moisture from rain and humidity. Drier foliage means less disease. You can grow vertically with wood stakes, tomato cages, or a trellis. On decks and patios, consider growing upside down, as mentioned in my previous posting The Weed-free, Organic Dinner Garden. Also you should prune the suckers from your tomato plants to help the air move through.
Use organic, preventative sprays. In a rainy season, you cannot wait for symptoms to appear and then go in guns blazing. It won’t work. There are organic sprays available to home gardeners that work biologically rather than chemically, with no toxicity to mammals or pollinators. The two most effective of these products are Serenade and Actinovate. Serenade triggers the plant’s natural defenses so that it’s ready for the fight when the bad guys show up. Actinovate inoculates the plant foliage with a microbe that makes the plant inhospitable to disease.
The key is to take action before you see problems. Remember, the tomato diseases are definitely coming; it’s up to you to decide how soon.