Sunflower Ash Rot

2024 Author: Gavin MacAdam | [email protected]. Last modified: 2023-12-16 13:38

Ash, or coal rot, in addition to sunflower, can also affect corn, beans, peanuts, potatoes and sugar beets. This attack is especially harmful in seasons accompanied by temperatures over thirty degrees and a lack of moisture. Sunflower harvest due to ash rot is often reduced by 25%, and in years with hot and dry summers, losses can even reach 90%. And you can face this trouble in all areas of sunflower cultivation

A few words about the disease

Ash rot usually manifests itself as a general wilting of growing crops in the second half of the growing season. The stalks attacked by it are painted in ash-gray tones, and inside them numerous microsclerotia are formed. The root system of infected crops is very poorly developed, and after some time, the roots begin to die off. And on the root collars of plants, brownish-brownish spots are formed, gradually covering the entire stems. Then the spots that have reached the stems brighten, acquiring an ashy shade. Infected stems noticeably soften, and their centers shrink and are often completely destroyed. In the middle of the stems, as well as under the epidermis, the formation of an impressive amount of black fungal microsclerotia begins. Slightly less often, pycnidia immersed in plant tissues can form on diseased stems. But the seeds and baskets are not affected by ash rot.

The causative agent of the ill-fated misfortune is the harmful fungus Macrophomina phaseolina (Sclerotium bataticola), which is characterized by a high degree of parasitism and a fairly wide distribution area. It is capable of infecting over three hundred varieties of wild and cultivated plants. Fungal mycelium, spreading in the parenchyma and epidermis of the stems, quickly destroys their structure. And it is localized mainly in the conducting system of the main roots, as well as in the lower parts of the stems and in the root collars. Gradually, the pathogen makes its way up the stems, provoking the wilting of the leaves and their subsequent drying. After a while, the infected plants die completely.

The incubation period at a temperature of twenty-five to thirty degrees is quite short and ranges from six to ten days, and tiny sclerotia can easily persist in the soil for five to six years. This usually happens when the weather conditions are not conducive to their active life.

It is noteworthy that the seed material obtained from infected crops is not a source of secondary infection, but at the same time it is characterized by reduced sowing qualities. The main source of infection is considered to be the remains of plants.

Despite the fact that ash rot affects sunflower in all areas of its cultivation (especially in semi-arid and arid), it is most often found in the south of Ukraine - there, regardless of weather conditions, the pathogen is observed annually.

The harmfulness of ash rot is quite high - there is practically no seed harvest from infected plants. This disease develops especially strongly in thickened sunflower crops.

How to fight

Among the main protective measures against sunflower ash rot, the use of tolerant hybrids and varieties, observance of crop rotation (the sunflower is returned to its former plots no earlier than eight years later) and pre-sowing treatment of seeds with fungicides should be highlighted. It is equally important to deal with weeds that contribute to the spread of infection.

If foci of ash rot are found, all infected plants must be removed from the site and burned. And the activation of soil antagonists of the pathogen and the mineralization of post-harvest residues will be facilitated by autumn plowing and timely stubble cultivation.