How to prevent and control gummosis in greenhouse apricots? A detailed practical guide
Apricot gummosis is a typical physiological disease caused by many factors, such as hail injury, insect injury, frost injury, sunscald, mechanical wounds, etc. It is often easily triggered during top grafting for variety change or large branch renewal, and heavy summer pruning, improper fertilization, heavy clay soil, excessive acidity, improper pesticide use and the resulting phytotoxicity can all induce gummosis. Only by understanding the disease's occurrence pattern can effective prevention and control be achieved. The symptoms, occurrence pattern and control techniques are described below:
Symptoms
Gummosis mainly occurs on branches, trunks and fruit. When the trunk and branches are affected, transparent gum exudes in spring; after contact with air, the gum gradually turns brown, becoming glistening soft gum masses, and finally turns tea-brown hard gum masses. The gumming sites are often swollen, and the cortex and xylem of the diseased parts gradually turn brown and rot, then become infected by saprophytic fungi, severely weakening the tree vigor. Fruit gummosis mostly occurs at wound sites; the gum sticks to the fruit surface, stunting fruit growth and reducing quality.
Pathogen
The pathogen of apricot gummosis consists of several species of Verticillium, belonging to the Deuteromycetes, Moniliales, Moniliaceae. It has been preliminarily determined that this pathogen is a saprophytic fungus that invades after gummosis is caused by physiological disorders, and after invading, it further aggravates the gumming phenomenon.
Occurrence pattern
The conidia of the pathogen spread through wind and rain, invading wounds or gumming sites. The fungus can lurk in the cortex tissue and xylem of affected branches, producing conidia in the dead cortex, which become the source of infection.
Control methods
(1) Avoid causing mechanical damage to the tree. If damage does occur, promptly apply lead paint preservative to the wound for protection.
(2) Promptly eliminate trunk-boring pests and control the amount of nitrogen fertilizer applied.
(3) During the tree's dormant period, apply a colloidal fungicide (prepared in the ratio of 1 kg latex + 100 g 50% thiram) to the diseased spots to kill the pathogen.