In 2009, most tomatoes grown in the eastern half of the country succumbed to late blight (Phytophthora) due to a cool, soggy June.
I live in the upper Midwest, along the Illinois–Wisconsin border, and my 'Black Krim,' 'Brandywine,' and 'Green Zebra' tomatoes were infected, too. Late blight had never been a problem previously, but we also had a chilly, rainy growing season.
Below photos show late blight lesions on tomato fruit and leaflet. Credit: Cornell University
When I lived and gardened in Texas, early blight (Alternaria solani) was a huge issue. I practiced pristine garden hygiene and mulched plants thickly to prevent the fungal spores of early blight from splashing up from the soil on to plant foliage when it rained or I watered. Late blight fungal spores, however, are airborne and invade everything that is susceptible, such as tomatoes, petunias, and potatoes. There is little defense other than chemical sprays once the fungal disease is spotted. That’s why commercial growers and home gardeners alike lost most of their tomatoes.
New Tomatoes to the Rescue
Plant breeders are offering us two methods to avoid blight damage in tomatoes this season: 1) grafted plants and 2) a hybrid bred to resist Phytophthora and Alternaria.
Any tomato variety can be grafted onto rootstock that is resistant to blight and other diseases. Asian, European, and Israeli horticulturists have been doing so for years. (Almost 95 percent of Japanese vegetables are produced from grafted plants.) Territorial Seed Company is exclusively offering several heirloom, paste, cherry, and beefsteak tomatoes grafted to 'Emperador' rootstock, which is highly disease-resistant. More companies will be bringing grafted plants to market soon.
There are a number of hybrid tomatoes bred to resist blight and other diseases. Johnny’s Selected Seeds teamed up with North Carolina State University to breed Defiant PHR, a midsize determinate tomato that is highly resistant to all strains of early and late blights. Other blight-resistant open-pollinated tomatoes are 'Santa' and 'Juliet' and 16-ounce tomato 'Legend'. 'Hefty Legend' was bred by tomato guru Dr. James Baggett at Oregon State University.
Given this year's extraordinary winter weather pattern and the climate extremes we’ve experienced in the recent past, I’ll be planting some of these blight-resistant tomatoes along with my usual heirlooms to make sure that I have a tomatoes for those first long-anticipated BLTs and salads.
If you have comments, questions about tomatoes, or tips for a better tomato garden, please share! Just post your comment below.