Hi, my name is: Early Blight of Tomatoes, nice to meet you

Describe yourself: I’m a saucy little fungal disease with a real thing for the leaves of tomato plants! People say I’m common, but I reckon I’m an angel, a brown spot with a gorgeous yellow halo.

Hobbies: I adore the older leaves of tomato plants, but don’t mind a stem, or entering the fruit through growth cracks or the fruit stalk. I’m movin’ on up baby… I start on your older leaves and work my way to the top of the plant, causing defoliation as I go. If I have to have a young plant, I would definitely go for the base of the stem… I’m partial to a bit of collar rot!

Likes: Oh, I love to get busy when the weather is over 15⁰C and there is lots of moisture around… it really gets my spores flying and my lesions growing! Love humidity, when you over fertilise your tomatoes (oh yeah baby, I love that), shade and water lying around on leaves. I love really crowded gardens where there is no air movement.

Dislikes: Sun, well mulched garden beds, when you clean up fallen leaves, hate well prepared soil with heaps of organic matter, home made spray remedies (like milk sprays and bi-carb mixes), store bought good sprays. I really don’t like gardeners who monitor their plants all year round!

You’ll know you’ve met me when: Your tomatoes lack serious vigour, older leaves are seriously ugly with spots, and some fruit shows damage (at the stalk end). Check young plants for collar rot.

Breaking up ain’t hard to do… if you

  • Mix fat-free milk with water in a 1:1 ratio and apply it using a spray bottle. Spray the solution directly onto the clean leaves of your tomatoes. Milk-and-water solution coats the leaves and leads to the growth of an invisible fungus that frightens off black spot!
  • To four litres of water, add 3 level teaspoons of bicarbonate of soda and a couple of good splashes of fish emulsion. Give it a good mix and spray it on weekly. Don’t apply when it’s hot. The Fish emulsion is very useful because it helps to make it stick. It also contains beneficial bacteria that have antifungal properties. And that’s not all – the oils in fish emulsion will help to suffocate pests like mites/aphids/scale. You must use it weekly for it to be most effective.
  • Seaweed sprayed onto the leaves changes the pH of the leaf surface making it less attractive to the fungal spores. It also strengthens the cell walls making it more difficult for the invading fungi.
  • Low Environmental Impact fungicides are available, but success is limited and control can be difficult.
  • Destroy all infected plants and dropped leaves by bagging and disposing in rubbish, or burning. Do not compost.
  • Rotate your crops!!! Don’t plant the same crops, or susceptible crops in the same area each season.


Banner Image:  Dwight Sipler from Stow, MA, USA – Early blight on tomato leavesUploaded by Jacopo Werther, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=25221133

Pic 1: www.avrdc.org Des: Fruit symptoms of Early Blight of Tomato
Pic 2: www.plantpath.iastate.edu Des: Foliage symptoms of Early Blight of Tomato
Pic 3: www.apsnet.org Des: Stem lesion caused by Early Blight of Tomato