Sclerotinia stem rot disease 

Cucumber diseases                                                             

Disease name: Sclerotinia stem rot disease 

 The scientific nameSclerotinia Stem Root 

  Disease family: Vegetable crops such as zucchini, cucumber, cauliflower, potatoes, tomatoes, lettuce and okra. It is one of the most devastating diseases of plants grown in cold temperate regions and attacks plants in the field or during transportation and marketing.

 Symptoms of the disease: One of the most important distinctive symptoms of this disease is the appearance of cottony growths, which are fungal threads that form on the stem, leaves, or fruits. The affected area becomes soft and watery, and its color may change to brown, resulting in the leaves wilting and falling, as the infection prevents nutrients from reaching that part, and it forms... Later - on the white cotton growths there are black stone objects ranging in diameter from 0.5 to 2 cm. In the event that the seedlings are infected near the area where the plant contacts the soil, this results in the death of the seedlings. However, the secondary infection may lead to partial death of the plant, that is, in the place where the germs that cause the disease arrive.

 The causes of disease: The disease is caused by the fungus Sclerotinia sclerotiorum (Libert) deBary, which is a fungus.

 Conditions suitable for the spread of the disease: High humidity and cold weather suit the development of the disease. The optimum temperature for the development of the disease is 18°C. Stone plants germinate in the cold, humid atmosphere when the temperature ranges from 12 to 20°C. Also, the availability of a thin layer of water on the surface of the plant is necessary for the germination of germs. Therefore, abundant irrigation water - especially the method of irrigation. Using sprayers - increases the chance of the disease spreading and infection developing

 Disease development cycle: During the absence of the host, it lives in the form of stone bodies in the soil, and when these bodies germinate, they form mycelium threads, or ascidian spores, from which the initial infection begins, and the disease spores spread through rain-laden winds and through irrigation water. The fungus secretes pectic enzymes that in turn break down the cells, killing the cells before the fungus reaches them. Mushrooms can be raised in an artificial environment in the laboratory, and the bodies form in the white, cottony growth medium on the nutrient medium. 

 Losses from the spread of disease: This disease is one of the most important diseases of warehouses and causes loss in the plant as a result of the death of the part located after the point of infection, and may cause the death of the plant completely if the stem is infected. 

 Control strategy: Initial monitoring of the field, eliminating weeds on an ongoing basis, and not planting on land previously infected with weeds. 

 Preventive measures to prevent the occurrence of the disease: Avoid plowing the land because not plowing reduces the chance of the disease developing and creating an agricultural cycle. 

Organic and chemical control recommendations:

1.  Use clean seeds that are free of stone objects and can be excluded by mechanical or manual sifting.
2. Moderate irrigation and improve soil drainage.
3. Treating small spaces using gas evaporators and solar energy for large spaces.
4. Follow an agricultural cycle by planting plants that are not infected for a period of no less than five years.
5. Ensure that the fruits or crop are free of infection before storing, inspect the crop immediately after harvesting, and preserve the fruits at the lowest possible level so that this does not affect the taste and flavour.
6. Spray plants in the field with fungicides as soon as symptoms appear. Repeat spraying once every two weeks until the disease stops using Rovral-Ronilan-Sumisclex. 

the reviewer : 

Garden and home pests - University of Jordan