Cherry blossom seedlings are susceptible to a variety of diseases and pests. The common diseases and pests and their control methods are described below:
I. Perforated brown spot disease
occurs from May to June. Small purplish-brown spots appear on the leaves, which gradually expand into circles. After the spots dry and shrink, they become small holes. The pathogens overwinter on diseased branches and leaves. The optimal temperature for development is 25℃ to 28℃. It spreads by wind and is more likely to infect during the rainy season. When the tree is weak, drainage is poor, and ventilation and light are poor, the disease will be more severe.
Control methods:
(1) Strengthen cultivation management, prune branches reasonably, and pay attention to cutting off diseased shoots. Clean up and burn diseased leaves in time to create clean growing conditions for the plants.
(2) Before the new shoots sprout, spray with lime sulfur solution at 3 to 5 Baume degrees. During the disease period, spray with Bordeaux mixture at 160 times or 50% benomyl wettable powder at 1000 to 2000 times, or 15% zineb at 600 to 800 times.
II. Leaf blight:
Yellow-green circular spots appear on the leaves in summer, which later turn brown and are scattered with small black dots. The diseased leaves wither but do not fall off.
Control methods:
(1) Remove and burn the diseased leaves, and spray Bordeaux mixture before budding.
(2) Spray 65% ​​zineb wettable powder at 500 times dilution in May and June, once every 7 to 10 days, for 2 to 3 times.
III. Crown gall:
Mainly occurs at the base of the trunk, and sometimes on the root collar or lateral roots. Tumors are produced in the diseased area. Initially, they are milky white or flesh-colored, and gradually turn brown or dark brown. They are spherical, with a rough, uneven surface and cracks. After infection, the root system is poorly developed, with very few fine roots. The above-ground parts grow slowly, the tree vigor is weak, and in severe cases, the leaves turn yellow and fall off early, or even the whole plant dies.
Control methods:
(1) Seedlings infected with crown gall must be destroyed in a concentrated manner. Before planting, it is best to soak the seedlings in 1% copper sulfate for 5 to 10 minutes, then wash them with water, and then plant them.
(2) Once a diseased plant is found, the tumor and surrounding tissue can be thoroughly removed with a knife or saw.
(3) Sulfur powder can also be sprinkled into the soil around the diseased plant at a rate of 50 to 100 grams per square meter for disinfection. At the same time, attention should be paid to soil improvement. (From First Nursery Station http://www./)