Try This Technique: Preventive Pruning for Tomato Early Blight


| 7/3/2008 1:08:26 PM


Tags: tomato diseases, growing tomatoes, early blight prevention, organic disease control, pruning,

Several seasons back, Jeff McCormack, Ph.D., founder of Garden Medicinals and Culinaries and Southern Exposure Seed Exchange, shared a tomato pruning method with me that delays the onset of early blight, and reduces the number of leaves lost in the course of the season.

Extension publications often suggest pruning tomatoes to prevent disease by improving air and light penetration. Jeff's method concentrates pruning at the base of the plant by removing leaves that eventually will be lost to early blight anyway. When the lowest leaves are removed just as the first leaf spots appear, you also remove millions of spores. And, because the bases of pruned plants dry quickly, the spread of the disease is slowed because early blight fungi need damp leaves in order to germinate and grow.

What's Early Blight?

The most common leaf-spot disease of tomato, early blight (Alternaria solani) fungi cause leaf spots to form on tomato leaves. Inside irregularly-shaped dry patches (which often have yellow margins), look for small dark rings. These are the fruiting colonies.  The grayish powder inside the dark rings are the spores, which splash or blow onto new leaves to form new spots. When spots become numerous, entire leaves wither to brown.

Commercially-grown tomatoes are often sprayed weekly with fungicides to suppress early blight. Organic growers sometimes use copper fungicides, which are often effective, but frequent use may harm earthworms. A few resistant varieties have been developed, but some failed to perform well in field trials, and others fall short in terms of flavor and texture.

Preventive Pruning

With big indeterminate varieties, prune or nip out all leaves that hang within 1 foot of the ground. If you see numerous lesions on the pruned leaves, you can go higher, to 18 inches. See the before and after photos below.



With stocky indeterminate varieties, trim out most of the leaves that touch the ground, but don't get carried away. If the plants have already set a heavy load of fruit, I also trim off some of the newest blossom clusters to keep the fruit:leaf ratio high. See the before and after photos below.

Sherri
5/13/2016 12:02:25 AM

how much Epsom salts and dry powdered milk do you put in the hole before the tomato plant?


bashmacs
7/2/2013 10:48:23 AM

do I really have to wait until plants are dry – in the midst of a very rainy week here in NC, and just noticing early blight – would like to go ahead and start pruning. on plants with blight, fruit is not showing yet, but flowering is in process. thanks!


bashmacs
7/2/2013 10:48:14 AM

do I really have to wait until plants are dry – in the midst of a very rainy week here in NC, and just noticing early blight – would like to go ahead and start pruning. on plants with blight, fruit is not showing yet, but flowering is in process. thanks!







mother earth news fair 2018 schedule

MOTHER EARTH NEWS FAIR

Next: August 4-5, 2018
Albany, OR

Whether you want to learn how to grow and raise your own food, build your own root cellar, or create a green dream home, come out and learn everything you need to know — and then some!

LEARN MORE