Early Blight is a fungal disease caused by the fungus Alternaria solani which lives in the soil. When rain or water splashes the soil up on the lower leaves, the fungal pathogen gets on the plant. It starts as some yellow mottling on the lower leaves which left unattended, then proceeds to work its way up the plant branch by branch on the leaves as shown on the photo above. It is contagious to the other tomato plants next to it so you should get on this pronto if you see any sign of it. Some tomato plants are more susceptible to it as well.
With all this cool rainy weather (we got 1″ on Tuesday night!) I have noticed more plants starting to get it especially as the season goes on. The older plants (just like people) get more susceptible to diseases as they get older. Here is a closeup of what it looks like on the leaves.
If you see any of this going on, you should immediately trim off all the branches that show signs of it. Be sure to disinfect your cutting trimmers between plants so as not to spread it. Your plant may not have many leaves left like this one.
I use a small container, pour some water in it to cover your trimmers and put some bleach in the water – 10% is good. But I don’t measure. I just pour some in-much less than if you were to put it in your laundry. The key is to dip the trimmers and your hand or hand in glove into the bleach solution and dry them off before I go to the next plant so not to pass the disease on to a healthy plant.
After you’ve trimmed off all the bad stuff, you need to spray with a good organic fungicide like Serenade to help slow it down. Also Copper Fungicide works but be careful using it. They are both organic fungicides. It’s best if you start the season spraying your tomato plants early BEFORE you ever have signs of Early Blight because then it’s a preventative but you may be able to control it if it hasn’t gotten out of hand, maybe not depending how bad it is.
Some of my plants (about 5 have it bad and don’t have many leaves left on because I trimmed them all off but they are loaded with tomatoes and the disease won’t hurt the fruit so I’m letting them stay in till I harvest and then I will pull the plant. It is interesting to note I only have one double row of tomatoes where it started with one plant and has now spread to 7 plants. (I already pulled out 2 others that showed it real early) Now I’m up to 7 plants out of 12 in the bed that have it. The rest of the beds look pretty good. I wish I followed my own advice but was crazy busy in the garden this year and wasn’t paying attention.
How to deal with Early Blight
1. After you plant the tomato transplants and make a well and add your drip system (if you have one), put straw all around the base to keep water from splashing the soil up on the plants. This applies for either hand watering or even if you have them on a drip system because of the rain. And just because you put straw around your plants doesn’t mean it won’t get the disease, but it helps most plants.
2. Start spraying ALL YOUR TOMATO PLANTS with Serenade as a preventative right away. It has a bacteria that won’t let the Early Blight bacteria colonize on the leaves thereby thwarting the disease. Plus it doesn’t wash off as the good bacteria attach themselves to the leaves. Do spray about every 2 weeks even if it doesn’t rain as a preventative.
3. Once it starts raining, spray weekly. Be sure to add more straw if soil starts to show.
4. When you first notice the lower leaves yellowing, cut away any branches with the disease present.
5. Disinfect with bleach water between cutting limbs off different plants so not to spread it. You can use bleach water as mentioned above or alcohol on the blades. I use bleach as I have a lot of plants and it’s cheaper.
6. Spray immediately after trimming but I would wait to trim if rain is in the forecast for that day. I like to let the spray dry and let those good bacteria attach to the leaves so I don’t trim on rainy days.
7. If your plant continues to go downhill, keep trimming and spraying and of course you should be spraying ALL of your plants not just the infected ones. You can move to Copper Fungicide if you have to but I always take the least toxic organic methods first. And just because it’s organic doesn’t mean it can’t be toxic. Copper is organic and yet is toxic in great amounts but doesn’t last long on the plant so just wash your tomatoes before you eat them. You can also pull the plant early if it only has tiny fruit on it or wait if it’s loaded with bigger fruit but be aware it might pass it on to other plants nearby, especially those that it touches.
This might not help as much this year but keep this info for next year.
PS—Early Blight is not like Late Blight found on the East Coast. Early Blight if caught early can be controlled. Late Blight is always terminal for a tomato plant if it gets it. Luckily we don’t get Late Blight out here in the Southwest. It is currently confined to the North East part of the US.