Prevention and Control of Leaf spot Disease of growing Apple

Apple spot leaf disease is an important disease of apple, which can cause early defoliation and tree weakness, which will not only affect the yield of the current year, but also affect the formation of flower buds and reduce the yield of the coming year.

1. Symptom

It mainly harms the young leaves, especially those within 20 days. In the early stage of the disease, there were small brown spots on the leaves and purplish-red halos around them. When the conditions are suitable, the disease spots are connected into pieces, and finally the leaves scorch and fall off. When the weather is wet, a black mildew layer grows on the reverse side of the disease spot. After the young leaves were invaded, the injured parts stopped growing, causing the leaves to shrink and deform, and some disease spots were ruptured and perforated. After the petiole and twig are damaged, oval brown sunken disease spots are produced, the leaves are easy to fall off, and the diseased branches are easy to break and wither. The damage to the fruit is mostly in the near ripening stage, the fruit surface produces brown spots with a diameter of 1-4mm, and the core is damaged, resulting in a brown to dark brown mildew layer, and in severe cases, it expands to the pulp.

two。 Prevention and cure method

The diseased leaves of ① in late autumn and early winter were burned and the diseased branches were cut off.

When ② entered the middle of June, the disease of apple shoots and leaves intensified, which was the main source of infection in the later stage. Cutting off these useless long branches in time and improving the ventilation and light transmission conditions of the orchard can reduce the disease.

③ apple spot leaf drop disease is generally only harmful to young leaves within 20 days, while apple trees have two new shoot growth times a year, in which spring shoot leaves play a decisive role in tree nutrition, fruit quality, yield and flower bud formation, so we should focus on protecting spring shoots and suppressing bacterial sources in the later stage. When the rate of diseased leaves reaches 5%-10% after spring shoot emergence, start spraying 10% Polaroid wettable powder or 50% prohydantoin wettable powder 1000-1500 times diluent, 80% Dasheng or spray gram wettable powder 1000 times diluent, 60% mancozeb wettable powder 1-2 times, autumn shoots can be sprayed once to control the disease.