Gray Leaf Spot on tomato

Stemphylium botryosum f. sp. lycopersici


Gray spot disease of tomato is caused by the fungus Stemphylium botryosum f. sp. lycopersici . The disease can be recognized by gray-brown spots on the leaves of the tomato and leaf loss due to desiccation. Under humid conditions and higher temperatures, severe infestation may occur.

Damage symptoms

Gray spot disease is usually limited to an infestation of the leaves. In exceptional cases, the petioles and stems of the plants can also be affected.

After infection has occurred, small, barely visible brownish spots initially appear on the lower leaves. The spots are roundish to elongated and distributed over the entire leaf blade. Usually, the spots remain small, about 2 mm in diameter. However, they can grow up to 1.5 cm in size and, when confluent, can cover larger leaf areas.

The spots have a lighter, necrotic center and are surrounded by a dark brown to brown-reddish margin. Under high humidity, a blackish-brown spore turf can be seen on these patches. On older leaves, larger leaf areas are affected and eventually die. When the centers of the spots dry out, they break out of the leaves. The leaves wilt, dry out very quickly, and fall off. Sometimes penetration of the fungus into the fruit also occurs from the stem ends of the fruit.

Host plants

The host plants of the fungus include plants from the Solanaceae family such as tomatoes or peppers, but also beans, asparagus, spinach, onion, kiwi, gladioli or blue lupins.


Gray spot disease is widespread throughout the world.

Propagation and transmission

The fungal spores are spread over long distances by wind. They germinate very quickly in the presence of water, especially in the form of dew, and warm temperatures (24 °C - 27 °C). Gray spot disease can already infect young plants and be carried along when transplanted to greenhouses.

The fungus survives on infested plant remains. It grows very quickly in the host tissue, so that the first symptoms are already visible two to three days after successful infection.

Prevention and control

Last updated: 23.11.2021

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