These diseases produce yellow leaves on tomatoes
Fungi and bacteria of the most varied of origins are urgently suspected of having yellow leaves on tomatoes. The following infectious diseases are possible and should be treated immediately:
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Leaf spot disease (Septoria lycopersici)
Watery spots with a black border develop on the yellowed leaves. As the process progresses, the leaves wilt and fall off. The fruits themselves are spared. Since they are no longer adequately supplied, the harvest is very small.
- remove and burn all infected leaves
- Spray the plant with skimmed milk
- Use certified seeds from specialist shops.
Bacterial wilt (Corynebacterium michiganense)
The foliage turns yellow from below. Cut stems show brown-yellow vessels. After flowering, most of the leaves fall off. Unsavory spots develop on the fruits.
- Rigorously remove and destroy diseased plant parts
- Pay attention to meticulous cleanliness when removing and pruning
- Loosen and sand compacted soil
- do not fertilize too nitrogen-stressed
These pests suck life out of the leaves
Among the usual suspects as the cause of yellow leaves on tomatoes, the following two pests stand out in particular:
Whitefly - (Trialeurodes vaporariorum)
The tiny, white flies and their brood mercilessly suck the sap from the leaves. The leaves turn yellow, are covered with sticky honeydew, wither and fall off.
- Spread a close-meshed insect net in the field
- Apply beneficial insects in the greenhouse, such as lacewings or two-point ladybirds
Thrips - (Thysanoptera)
The black fringed winged birds produce yellow leaves in two ways. The adult insects suckle on the sap, while the larvae nibble on the roots.
- Spray tomato plants with the classic soft soap solution
- alternatively powder with primary rock powder
- blue glue boards catch the thrips
- Use beneficial organisms such as predatory mites and hoverflies
The solution to the riddle for yellow leaves: nutrient deficiency
If diseases and pests can be ruled out as the cause of yellow leaves, the experienced hobby gardener is far from at the end of his or her mind. An inadequate supply of nutrients is targeted. If the following minerals are missing, the starving tomato plant reacts by yellowing its foliage:
- Eliminate nitrogen deficiency through targeted fertilization with nettle manure
- older leaves turn yellow; magnesium, potassium or phosphorus are missing
- if young leaves turn yellow, there is a lack of iron, zinc or copper
Tips & Tricks
A professional soil analysis provides a well-founded knowledge of the exact composition of the soil in the tomato patch. Qualified laboratories have specialized in this and offer this service at a reasonable price. With the help of instructions, soil samples are taken and sent by post. The laboratory not only provides an informative result, but also gives practical suggestions for fertilization.