Why Do Apricot Fruits Develop Black Spots
The apricot tree is a deciduous tree. The fruit borne on the apricot tree is not only delicious, but its branches, seeds and leaves all have different uses. Although it is an important economic fruit tree, various problems are encountered during cultivation. Why do apricot fruits develop black spots?
1. Why do apricot fruits develop black spots
Black spots on apricot fruits may be caused by infection with scab, a fungal disease. When the fruit is infected, small dark green round spots initially appear mostly on the skin of the fruit. As the fruit swells and ripens, the spots enlarge and their color deepens. In severe cases the spots merge into continuous patches, and the fruit skin becomes cracked.
2. What is apricot scab
This disease is widely distributed and common in the northern regions of our country, mainly harming the fruit, but also harming the branch tips and leaves. When the fruit is infected, small dark green round spots initially appear mostly on the skin at the shoulder of the fruit. As the fruit swells, the spots enlarge and their color deepens, later gradually turning brown and purplish red. When the fruit surface turns yellow and the fruit is nearly ripe, purplish black or reddish black mold-like spots appear on the lesions. In severe cases the spots merge into continuous patches, the fruit surface becomes rough and cracking forms.
On ripe fruit, the lesions are patch-like and grayish brown, and the fruit skin cracks irregularly, often with gum exudation.
When the branch tips are infected, oval light brown small spots first appear on the diseased part, with purplish brown edges, later turning blackish brown and slightly raised, with dense small black granules on the surface. After several lesions merge into patches, the upper branch tips of the plant may die. When the leaves are affected, irregular or polygonal grayish green spots appear mostly between the veins on the underside of the leaves, gradually enlarging and turning brown or purplish red. The diseased part dries up and forms holes, and in severe cases causes early leaf drop.
The pathogen is called Cladosporium carpophilum, a fungus of the Deuteromycotina. The pathogen overwinters as mycelium on the lesions of the current year's apricot branches, and in April to May of the following year produces conidia, which spread by wind and rain to cause re-infection. The incubation period of this disease is long, and the primary infection is the most harmful to the apricot tree. The germ tube produced by germinating conidia can directly penetrate the cuticle of the host epidermis and invade. The initial onset of the disease is generally in May, and the peak period is from June to August. A spring and early summer with more rain, low-lying and damp orchards, and a dense canopy with poor ventilation and light penetration all favor a more severe occurrence of this disease.
3. Control measures for apricot scab
1. In combination with winter pruning, promptly remove diseased branches, diseased branch tips, mummified fruit and other diseased plant residues from the tree and the orchard, carry them outside the orchard and burn them in a centralized way to reduce the primary infection source.
2. Apply more fully fermented and decomposed organic fertilizer or organic-inorganic biological compound fertilizer containing humic acid, and fertilize according to the fertilizer requirement pattern of apricot growth, to enhance the disease resistance of the plant.
3. Before the flower buds break in spring, spray 5 degrees Baume lime sulfur mixture or 21% peracetic acid aqueous solution at 300 times dilution.
4. After the flowers fall, spray chemicals once every half month for control:
(1) 21% peracetic acid aqueous solution at 375 times dilution + 80% Dingjia (fully complexed mancozeb) wettable powder at 900 times dilution.
(2) 25% azoxystrobin suspension concentrate at 1500 times dilution + 25% difenoconazole emulsifiable concentrate at 3000 times dilution.
(3) 40% flusilazole emulsifiable concentrate at 7500 times dilution + 75% chlorothalonil wettable powder at 450 times dilution.
(4) 43% tebuconazole suspension concentrate at 4500 times dilution + 50% chloroisobromine cyanuric acid wettable powder at 750 times dilution.
When growing fruit trees, some pests and diseases are unavoidable, and control measures need to be carried out well according to the actual situation.