Dealing with Tomato Blight
By Michael Nolan
Early Blight
Looks like: Darkened spots on the older leaves, with rings. The area around the spot will often turn yellow.
Treatment: The fungus that causes Early Blight can survive through the coldest of winter months in the soil. The only way to avoid Early Blight is to completely remove any affected plants and clean all of the garden debris in the area. Some experts say that copper or sulfur spray will stop the fungus from spreading.
Late Blight
Looks like: Late Blight is what caused the infamous Irish Potato famine. It presents as a gray spot on the leaves that looks almost like a grease spatter, and will often be surrounded by white mold – especially in wet weather.
Treatment: This fungus is like Early Blight in that it can survive mild winters. It can also transmit to potato plants and has been known to survive even cold winters, so the same treatment is called for.
Southern Blight
Looks like: White mold appears near the base of the plant, leading to darkened circular spots on the stem that stops water and nutrients from getting to the fruit.
Treatment: Rotating crops every year can keep Southern Blight to a minimum. Some studies have also shown that fertilizers with added calcium or ammonium can help.
Next week we’ll look at a few more diseases and fungi that can affect your tomato crops. If you have any unusual symptoms rearing their ugly heads in your tomatoes, drop me a line and I’ll do my best to help you get through it!
June 14th, 2008 at 8:09 am
Oh, that picture makes me want to cry!
June 14th, 2008 at 12:19 pm
I think my tomatoes had blight last spring after a long period of rain. They were growing in containers on my deck. I still got a few tomatoes, but not the bountiful harvest I had been dreaming of.
June 14th, 2008 at 4:06 pm
Gack! As if hornworms and blossom-end rot weren’t bad enough. And then there are all those fusarium and verticillium wilts. Poor tomatoes! Suddenly, growing them in containers is starting to look like a *really* smart idea…
July 23rd, 2009 at 11:42 am
try mulching with cedar chips. we have good toms with no blight or rot !
August 8th, 2009 at 8:30 pm
I disagree about the cedar chips; we did that & the roly polys LOVED it. They ate ALL of my zucchini’s, cukes, etc. Rhubarb still hasn’t recovered. This year we replaced all of the dirt in our beds & now we have Japanese beetles and tomato blight. BTW, I bought my plants at a reputable local nursery.
August 28th, 2009 at 12:37 am
[...] enough, and no other markings have shown up on the rest of the fruit. In addition, if it was blight the tomatoes would tend to rot from the head down, not from the bottom up, like my guy. It [...]