Monday, July 30, 2012

Late Blight

Blight is one of those words that make all organic vegetable gardeners cringe. We are not strangers to early blight here. It is a disease common in our area, and once you get it in your soil you never really get rid of it. Early blight is somewhat manageable. You have to continuous prune off the affected leaves, and you can spray with compost tea, milk wash or an organic fungicide like Greencure. Early blight can be quite destructive during humid wet conditions, but most years i am still able to harvest a good amount of tomatoes before the plants die back.

Early blight is easy to identify. It usually begins on the lower leaves, and starts as irregular brown spots surrounded by yellow halos. As the disease progresses, you'll start to see brown spots on the stems as well.

This year i got hit with Late Blight. Late blight is one of the most devastating diseases of potato and tomato worldwide. It was responsible for the devastating Irish potato famine of the 1840's and can result in complete destruction of potato or tomato crops.

When i first noticed the brown spots on the leaves, i didn't really think much of it. We get early blight every year, and although the spots were lacking the yellow halo i still assumed it was just early blight.

i have been extremely excited about my tomatoes this year. i planted 40+ tomato plants all heirlooms , many started from seed. All summer i have been dreaming of canning pasta sauce and salsa, of eating fresh tomato sandwiches with big fat slices of Cherokee purples.

i have been watching my tomatoes obsessively. Picking off the early blight, adding fresh compost around the bases, spraying with Epson salts when they showed early signs of magnesium deficiency. i brewed Comfry tea and manure tea to give them extra nutrients to create strong healthy plants. They were looking incredible. My plants were huge, dark green and loaded with huge fat green tomatoes. i was already envisioning my best tomato year ever.

Then the rain started.

It rained, and rained and rained. The evening temps became strangely cool for July, brown water soaked spots began to appear on a few of my tomatoes, and then three of my beautiful heirloom plants, shriveled and died almost overnight.

i really had no idea what could have happened, but i pulled and burned the plants and continued to monitor the others. Then i received an email that made my heart sink. The email subject was Late blight Alert in Floyd County. i immediately began to research late blight.

Late blight typically appears during periods of wet cool weather. It first appears as water soaked brown spots, with fuzzy white on the backsides.
i knew immediately that is what had killed my plants so quickly. Late blight can kill an entire tomato crops within a week if the conditions are right. It spreads quickly, and is resistant to most organic pesticides and treatment. The most effective organic protectant is copper. This should be applied to your plants before you notice signs of late blight.

Once you see the spots, there is very little that can be done. i purchased bionide copper fungicide and immedatly began spraying all of my tomatoes (i have three separate gardens with tomatoes planted). The first plants died around July 21. By July 24 i had found late blight just beginning in a second garden. By July 26th, all of my tomatoes had the spots.

Less than a week ago this was a beautiful, healthy, lush plant and in just a few days almost all of the foliage is gone. The plant will be dead by the end of the week.

Besides the damage to the actual plants, the tomatoes themselves are affected by late blight. The green tomatoes often develop brown lesions which can affect the entire tomato. If allowed to ripen on the vine, the tomatoes will just rot. From what i have read, if picked green and allowed to ripen the tomatoes may turn red, but will not sweeten and the flavor will not be great.

Also tomatoes affected by late blight are not suitable for canning.

This is by far the most devastating disease i have ever experienced. i have 100+ lbs of beautiful green tomatoes that will never ripen. :( i really can't even begin to express how heart sick i am over the loss of all these tomatoes. Because i can not bring myself to throw them out, i've started compiling a pinboard of recipes that use green tomatoes.

Although this years tomato crop will not fill my cupboards with jars of sauce and salsa for the winter, it is not completely wasted.

In trying to stay optimistic about the situation, the one positive thing is that Late blight does not over winter in the soil. The pathogens should be killed off during the winter, and it really requires specific weather conditions to appear and spread. So the likely hood of getting it again next year is not a guarentee. Also, because i now know what to look for, it is were to appear again i can remove the plants immediately and begin treating the others before it becomes a total loss. i've been gardening for 12 years, and this is a first. It is devastating, but also a learning experience.

Despite the gardener's best intentions, Nature will improvise. ~Michael P. Garafalo


  1. Ugh, I'm so sorry.

    I noticed one of my tomatoes had a brown blemished area with white fuzzy stuff in the middle yesterday. But the plants don't have any spots. Wonder if it could be starting here?

    1. i would watch your plants. Tomatoes occasionally get spots because of a variety of factors. Growing conditions (too much rain/not enough rain can cause spots that look similar to plant diseases. If you get late blight you'll know within a matter of days. It spreads incredibly rapidly. It typically starts on the plant.