Are Your Tomato Plant Leaves Showing These Symptoms?

Photo by jayneandd.
We all want great tomatoes from our tomato plants, but often the plants are hit by diseases or pests and although some fruit develops wouldn’t it be nice to maximize the yield from each plant to get a killer crop, by curing the diseases or getting rid of the pests?

The first thing to do when you notice a not so healthy looking plant is to find out exactly what is going on, so that you can begin you search for the cure. Below is a list of symptoms together with possible causes to get you going on your quest to grow the best possible tomatoes. Try doing a Google image search once you get an idea of what your tomato plants are trying to tell you, and see if it looks like what you’re seeing on your own tomato plant leaves.

Discolored leaves

Yellow

As you can see below, a yellow coloring of your tomato plant leaves can be caused by many different things. The color yellow either covers the entire leaf, is limited to patches or limited to just spots, depending on the cause:

A lack of nitrogen affects the lower leaves. It spreads to the upper leaves.
A lack of calcium affects the upper leaves
A lack of manganese is rare, but will result in dead patches on the leaves, ringed in yellow
Wilt diseases can cause a shortage of nutrients, which will then result in a discoloring of leaves
Fusarium Wilt affects older leaves
Verticillium (Verticillium dahliae)
Leaf spots (Early Blight or Target Spot)
Root rot
Mosaic virus results in mottling
Aphids
Spider-mites can cause a white-yellow speckling

Light green

Too much nitrogen
A lack of manganese

White

A lack of iron
Powdery Mildew results in powdery patches

Black

Fusarium Crown Rot

Curling leaves

A lack of potassium affects older leaves
A lack of iron
A lack of copper is rare, but results in blue-green flappy leaves
Curly Top virus affects upper leaves and results in a purple-like color

Spots on leaves

Brown

Early Blight or Target Spot (Alternaria solani)
Late Blight (Phytophthora infestans)

Dark

Bacterial Speck (Pseudomonas syringae)
Bacterial Spot (Xanthomonas campestris pv vesicatoria)

Purple

Late Blight (Phytophthora infestans)
Tomato Spotted Wilt/Impatiens Necrotic Spot Tospoviruses

Wilting leaves

Fusarium (Fusarium oxysporum f.sp. lycopersici)
Fusarium Wilt
Fusarium Crown Rot
Verticillium (Verticillium dahliae) can result in wilting at midday but recovery at night
Bacterial wilt (Ralstonia solanacearum)
Root rot
Tomato Spotted Wilt/Impatiens Necrotic Spot Tospoviruses (TSWV or INSV)
Nematodes causes the plant to wilt prematurely
Walnut toxicity if the plants grow near a walnut tree

Drooping leaves

Fusarium (Fusarium oxysporum f.sp. lycopersici)
Fusarium Wilt
Fusarium Crown Rot

Flies on leaves

Whitefly (1 mm), more often seen in a greenhouse than out in the open
Thrips (1 mm), onion thrips (Thrips tabaci) and flower thrips (Thrips obscuratus)
Fruit fly

Removing some of the leaves

If the problem is that you have too many tomato plant leaves then here are some tips on removing some of the leaves to provide the plants with more sunlight and oxygen:

Single vine variety: All ‘suckers’ can be removed and staking should first be done after the first flowers appear to create a strong plant.
Multi-stemmed variety: All stems should have the same size. Any side stems below the first flower cluster can be removed to create a strong main stem.
Determinate variety: ‘Suckers’ below the first flower cluster can be removed.
Sterilize knife or scissors between plants, or use your fingers to pinch of unwanted leaves and branches
Remove branches during dry days to avoid bacteria getting into the ‘wound’ because of rain
Remove sick leaves and branches to reduce spreading of diseases
You can reuse any clippings – they will grow into new plants if you stick them into the soil!

Cucumber leaves

I haven’t been able to find any evidence saying that tomato plants can’t rub leaves with cucumbers. I think it’s a myth and more a question about space. Cucumbers grow big leaves, and they could overshadow a tomato plant if the plants were standing close.

While it should be safe to grow cucumbers near tomatoes, there are some plants that are even recommended companion plants for tomatoes, like French marigolds (Tagetes patula), because they deter nematodes. Other plants that act as pest control are: