Avoiding Late Blight In Your Tomato Garden

In 2009, Pennsylvania and many eastern and mid-Atlantic states had a terrible problem with Late Blight on tomatoes. So much so that many gardeners and farmers lost their crops to this disease. Some blamed blighted tomato plants bought at big box stores, but most likely it was simply due to a very rainy and cool growing season.

Now that it’s about time to plant this year’s tomato plants, how can you avoid tomato blight this season?

The fungus that causes blight can overwinter on foliage, so it’s essential that you destroy any previously infected plants. By destroyed, I mean burned or bagged with your garbage, not composted. If any diseased plant debris is still laying in your garden, destroy them now and til that bed deeply. Then cover the bed with lots of compost and work that into the soil as well.

Wait at least two seasons before planting tomatoes in a previously diseased garden bed – this is one of the first principles of crop rotation. If that disease was blight, you’ll have to be especially vigilant – plant this year’s tomatoes as far as possible away from the diseased bed, because the blight fungus can be airborne. One blighted garden tomato plant can spread the fungus spores for miles and ultimately infect entire communities.

If you destroyed your blight infected plants at the end of last year, you should be safe. Additional steps you can take this year are:

Plant heirloom varieties. Heirloom plants have survived for generations, sometimes hundreds of years, so they may have natural resistance to many diseases, including Late Blight.

Plant varieties that are well adapted to your area. This is recommended by most scientists, but I planted Brandywines last year (adapted to this area of Pennsylvania) and they were among the first to develop blight. So take this advice with a grain of salt.

Change the way you water your plants. This is the most important step. Most blight fungus starts on the leaves and stem of the tomato plant. Keep these parts of the plant dry – water the root areas only and only when necessary. You’re always better off giving your plants a good soaking once per week instead of watering them lightly a number of times during the week. You might want to consider switching to drip irrigation or soaker hoses for your watering. These methods also conserve water.

Be aware of early signs of late blight and other diseases and take the appropriate steps to alleviate the symptoms if they appear. You can find more specific info at these sources:

• University of Minnesota: Late Blight of Tomato and potato
• Cornell University: Septoria Leaf Spot Of Tomato
• Cornell University: Potato Early Blight
• Track reports of blight at USABlight.org