What’s Wrong With My Tomato Leaves?

At this time of year those who grow tomatoes often see signs that the plant isn’t thriving as they’d like. Holes in the leaves, yellowing of the tomato foliage, or brown, dying stems are common. Like damage on other plants, however, we should never assume that what we see is all related. When it comes to tomato plants some leaf problems are serious and need action, and others are cosmetic only and don’t affect fruit production.

Here is a tomato plant in our community garden plot that has an assortment of symptoms on the leaves.

Here are the three problems seen on this plant (a cherry tomato that has tiny-sized fruit) and information about what should be done to help this plant.

Many of the leaves have small holes in them. People often assume that such holes are caused by insects, but often it’s a fungal problem. These holes are a leaf-spot fungus that kills small bits of the tissue which then falls out. It’s doing minor damage to the plant. Leaf spot is often made worse by frequent irrigation and splashing of foliage with water. Avoid watering too frequently (soak the garden deeply less often) and avoid watering in the evening. Watering in the evening or at night keeps the foliage wet all night which promotes fungus.

There are a few browned stems on this plant as well. Sometimes brown, dead stems are a sign that blight is progressing, and sometimes these are just stems that got broken or cracked earlier in the summer. The stems that are dead on this plant look like they might have been damaged when the main part of the plant was tied up, by a bird landing on them, or by heavy winds when the plant was young. Brown lower stems may also be a sign that the plant dried up earlier in the season in between waterings.

This plant also shows some leaves that are yellowing with dark spots in those areas. In this area this is commonly caused by Early Blight. This is also a fungal disease and it normally progresses from the bottom of the plant up. Unlike the random leaf spots that make small holes, this fungus will kill the tomato plant if left untreated.

So what’s to be done if you see such symptoms on your tomato plant?

1. Clip off the brown, dead stems so that it’s easier to monitor if the damage is continuing.

2. Ignore the tiny holes but remove all leaves showing signs of Early Blight. Spray the plant weekly with an organic fungicide to slow the progression of the blight. Next year begin spraying with Serenade weekly, starting as soon as the plants are placed in the ground. If the Early Blight gets worse (and it often does) switch to a copper fungicide for the remainder of the season.

3. Water deeply every 4 to 7 days depending on the weather. When the nights are cool and days below 85 you can water less often, but when you do water, be sure that the entire area around the plants get soaked down at least 12″. Usually hand-watering isn’t enough because people get bored before the plants are watered well, and they tend to direct water only at the base of the stem not out beyond the dripline. Whenever possible – with the exception of containers – water with soaker hoses or a sprinkler not by holding the hose in your hand or using buckets. Water in the morning whenever possible so that the foliage dries quickly.