Tomato Disease-more info on Early Blight

Early BlightSomeone replied to my last post on Early Blight, “Will this contaminate the soil (for next year)?” Great question. Here is more info on this subject.

If you have a garden, it’s pretty much in the soil. One key is to provide a barrier between the soil and your plant, hence I add straw as a mulch around them to act as a barrier and use fungicides to catch it early or before it starts.

Some years are better as they are drier but when you have a wet summer, it can be a problem. I’m not sure if you took out the soil if that would help because who can remove all the soil? Unless you put them in pots-maybe that would work.

You should consider crop rotation, not growing in the same spot for 2 years and then coming back to it 3 years later. Crop rotation is used to control diseases that can become established in the soil over time. Changing your tomato crops to a new bed or area tends to decrease the population level of the pathogens.  That is why I have 3 sections in my garden so I can rotate the tomatoes to a new section each year. If you have raised beds, you could rotate the tomatoes to a new bed each year coming back to the original bed 3 years later to get the same effect.

I don’t look at Early Blight as a major killer of tomato plants if we do close monitoring and take action. By using fungicides early on and crop rotation every year, we can usually control it.

Also good clean-up in the fall after the garden is done is important. Do not compost the dead plants but bag them and put in the garbage.

You can read the first post about Early Blight here.


Tomato Disease-Early Blight

early blight_plant

This is a tomato with severe Early Blight. Notice it has worked it’s way up through the plant. I should have removed the diseased leaves while it was till on the bottom leaves and then sprayed with Serenade. I may not be able to save it.


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.

Early Blight

Closeup of Early Blight on lower leaf

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.

tomato plant trimmed

Tomato plant trimmed off of all diseased leaves-notice there are hardly any 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.

bleach water

Use a 10 % bleach solution in water to disinfect trimmers

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.

tomato fungicides

I Start with Serenade and then move to Copper Fungicide if it gets worse. Be sure to wash your tomatoes really well if you use the copper fungicide. Both are organic but the copper fungicide is stronger.

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.

Master Gardener Tomato Disease Sheet

Hey Master Gardener Interns! I want to let you know you all were awesome with some great questions and suggestions. I really enjoyed the classes. I thought I’d put it in my post below so others can read it as well as the pdf here TOMATO DISEASES in case some of you didn’t get one.  (It’s easier to print off the pdf than the post). This is not a complete list of tomato diseases in New Mexico but some of the most common. Also the HERB SHEET is two posts back for you to get.


Most tomatoes are susceptible to Early Blight which usually develops in early summer, after heavy rains or when it is humid and warm.
SYMPTOMS: Leaves at the base of the plant near the ground develop dry looking, irregularly shaped brown patches surrounded by concentric
rings. The best prevention is prune off the affected leaves as soon as you see them. I prune off all branches and leaves within 18 inches of the ground to try to prevent this as it is a soilborne disease. Early Blight overwinters in the soil. Remove affected plants and clean up fall garden debris as it overwinters in plant residue. Wet weather increase likelihood of getting this disease.
CONTROL: Protectant fungicides-Copper or sulpher can prevent further development of it, Green Cure (potassium bicarbonate), and Serenade (QST 713 strain of Bacillus subtilis), a biofungicide helps more to prevent
disease and is not a cure. Also spacing plants farther apart for good air circulation may help. Good sanitation and disposal of plants at end of season are important.


Septoria leaf spot can occur and any stage of a tomato plant development especially after heavy rains or when it is wet and warm. Spores are spread by windburn rain, insects, splashing rain
SYMPTOMS: It’s usually observed first on the lower leaves. Leaves that are heavily infected have small circular brown spots, turn yellow, dry up and drop off. The fungus is not soil inhabitant but can persist from one season to the next if the debris from the diseased plant is not removed and ends up in the soil.
CONTROL: Copper fungicides, Green Cure (potassium bicarbonate), Serenade (QST 713 strain of Bacillus subtilis), a biofungicide, helps more to prevent disease.

Bacterial Wilt

Soil borne and waterborne pathogens that causes leaves to wilt in day only to recover at night and then complete sudden wilting of plant.
TEST: Cut a four inch long section from low down on the stem and suspend this cutting in a jar of water. If a cloudy, milky ooze comes out, this in an indication of bacterial wilt. Dried leaves may remain green.
CONTROL: Dispose of plants. Plant in different location. 3-4 year rotation
of crops

Transmitted by the beet leafhopper which build up high numbers on tumbleweeds and survive the winters on mustard plants.
SYMPTOMS: upward curling leaves that become thick, stiff and twisted. May stay green or become yellow with purple veins, plants become stunted. Plant next to them may be virus free.
CONTROL: Provide partial shade is beneficial as leafhoppers prefer to eat in the sun. Possibly use row cover/shade cloth to cover plants.

Tomato Spotted Wilt in tomato

Tomato Spotted Wilt


This virus is caused by thrips that transmit the virus from infected tomato plants to other healthy tomato plants.

SYMPTOMS: Two symptoms are dominant- young leaves turn bronze and develop small brown spots. Second, the leaves wilt and tips die-back. Infected plants produce poor quality fruit and less yield. Pull plants and dispose of them.
CONTROL: Elimination difficult. Using reflective mulches may help reduce
infection, physical barriers like covering plant with row cover when it is young.

Hard brown or black leathery patches on the blossom ends of ripening tomatoes indicate blossom-end rot. It is more common in large fruited varieties. This is generally caused by a calcium deficiency at fruit set or uneven watering and is prevented by planting tomatoes in compost enriched soil and mulched with straw to keep moisture levels more constant. I put a tablespoon or two of dry milk in the bottom of each hole when first planting tomatoes. In the fall dig in some gypsum which is a good source of calcium without raising the ph of the soil here in Santa Fe.