One of the most common diseases in tomatoes is the late blight Phytophthora infestans. It lowers the fruit yield, especially in conditions of high air humidity on cold days.Infected tomatoes are also attacked by other pathogens and are not suitable for further processing.The first symptoms appear at the end of May, and later in less favorable weather conditions.
At first, watery, yellowish-brown spots can be observed at the edges of the leaves, and then brown, misshapen, gradually enlarging spots. The fruit has brown, slightly convex spots, clearly harder than the he althy part of the fruit.The borders of the spots are not sharp. The browning extends deep into the flesh and may cover the entire fruit in the next few days.
Favorable weather for the development of late blight means frequent and abundant rainfall, high air humidity, temperature around 15-18 ° C and long-lasting wetting of the leaves.In conditions of high air humidity on the underside of the leaves, on the border of he althy and infected tissue, a delicate white coating can be seen.In protecting tomatoes against blight, careful harvesting and destruction of infected plants is recommended.
Does the so-called potato blight on tomatoes result from sudden temperature changes?
No. The late blight of potato, characteristic of nightshade plants and causing serious losses in the yield of potatoes and tomatoes, is a disease from the group of phytophthora, diseases caused by fungal-like species of oomycetes.The pathogen Phytophthora infestans is responsible for the plague, whose spores are successfully spread by wind and water. Infections of potato tubers and tomato fruit are more severe during harvest, when direct contact with spore-bearing parts of the plant may occur. Temperature (but not its rapid changes) plays a role in spreading the pathogen. Phytophthora infestans is favored by temperatures above 10 ° C (preferably 15-18 ° C) as well as frequent rainfall and high air humidity.
- says Dr. Eng. Tomasz Mróz
The plants must not be fertilized with nitrogen, because it promotes infection. Chemical treatments are the primary method of protecting tomatoes against late blight.The first spraying is performed just before the occurrence of favorable conditions for infection or at the latest when the first disease symptoms appear on the plants. The best way to combat it is to use one of the systemic fungicides first.
