What to do about leaf curl disease in plum blossoms? Causes and control methods

Causes and control methods of leaf curl disease in plum blossoms. So-called leaf curl disease refers to plum blossoms under water-deficient conditions, where both sides of the leaf fold inward toward the center of the upper surface and curl, showing a listless, wilted state; it is a physiological disease. Leaf curl disease not only affects the beauty of the plum tree, but in severe cases can cause leaf drop.

Causes of leaf curl disease: In the Yangtze River basin, summers are hot with little rain, the soil is dry, air humidity is low, and light is intense, while the plum tree itself has a relatively poor ability to transport water. Its leaves are numerous and thin in texture, and water evaporates relatively quickly, so leaf curling is extremely likely to occur when water is deficient. Leaf curling begins from May to June and can continue until August to September. After rain, the leaf curling eases somewhat, and the leaves flatten out slightly.

With timely irrigation and an adequate water supply, mass leaf drop will not occur, nor will it affect flower bud differentiation. Control methods: Plum leaf curl disease results from the combined action of the plum tree's own special anatomical structure and physiological characteristics, as well as adverse climatic factors. Therefore, in the vast plum cultivation areas, it is impossible to keep plum leaves in a normal flat state throughout the entire growing season. By strengthening management so that the root system grows and develops well, with well-developed fine feeding roots and a sturdy tree body, the plant's water absorption and transport capacity is enhanced, thereby avoiding or reducing the occurrence of leaf curling. During hot, dry seasons, watering and foliar spraying should be carried out promptly to ensure that curled leaves do not drop due to being overly severe.

How to control leaf curl disease in plum blossoms

Leaf curl disease is a physiological disease. In ground-planted or potted plum blossoms, under water stress, both sides of the leaf fold inward toward the center, and the entire plum tree appears listless, tired and wilted; in severe cases it causes extensive leaf drop.

Causes

On the one hand, it is due to high summer temperatures and little rain, dry soil, dry air, and excessively strong light; on the other hand, the plum tree itself has fine fibrous roots with a relatively poor ability to absorb and transport water, and plum leaves are rather thin, while at this time the plum tree evaporates water relatively quickly. Because overall water is in a deficient state, its leaves curl, with the “Green Calyx Plum” variety being the most severely affected. Leaf curling begins around June; after rain it eases somewhat and the leaves can flatten slightly. When the weather is favorable and water supply is adequate, leaf curling appears later, there will be no mass leaf drop, and flower bud differentiation will not be affected.

Control methods

Leaf curling is caused by the combined effect of the plum tree's own special structure and physiological characteristics, as well as adverse climatic factors. For this reason, strengthen management so that its root system develops well and the tree grows robustly, thereby improving its water absorption and transport capacity; after entering the hot, dry season, strengthen root watering, foliar spraying and environmental sprinkling, creating a relatively cool environment for it by increasing humidity and lowering temperature; for potted plum blossoms, especially shallow-pot plum stumps, and particularly for the “Green Calyx Plum” variety, a shed can be built for shade, with the shading level controlled between 30-40%, just enough to protect the curled leaves from dropping due to excessive dehydration.

Control of plum leaf blister disease

1. Damage symptoms

It mainly occurs in spring. The first to be damaged are newly sprouted tender buds and new leaves; the internodes of tender shoots become thicker and shorter, leaves grow densely, the leaf surface wrinkles and thickens, becoming fleshy, with a rough surface, curling toward the leaf underside. Diseased leaves are initially yellow, red or purplish red, then gradually turn grayish white, with a powdery substance appearing. In severe cases, diseased shoots die, tree vigor weakens, and flower quantity decreases.

2. Disease occurrence pattern

It overwinters as ascospores and blastospores on diseased shoots inside and outside the host buds' scales. The mycelium is annual or perennial; blastospores have two types, thin-walled and thick-walled. The former can continue budding, while the latter has the function of dormancy and resistance to adverse environments; after surviving adverse conditions, it germinates again to form blastospores that infect the host. The next year, the pathogen begins infecting in early April, the disease occurs more severely in early May, and stops occurring in June. The pathogen infects once a year, and re-infection occasionally occurs. However, due to high temperatures and unsuitable conditions, the damage is not significant. A cool, moist climate is most suitable for spore germination and infection. Around 20°C nba betting is most suitable for pathogen growth; at 28°C pathogen growth is inhibited and the disease cannot occur. Continuous overcast rain or foggy weather in early spring is unfavorable for disease occurrence.

3. Control techniques

1. If pruning is needed in winter, be sure to pick up fallen plum leaves and plum branches cleanly and sweep the plum garden clean. In conjunction with winter pruning, during topdressing management, apply more fully decomposed high-quality organic fertilizer and phosphorus-potassium fertilizer, and apply less or preferably no nitrogen fertilizer, to promote robust growth of plum branches and leaves and improve the plant's resistance to plum leaf blister disease.

2. If pruning is needed in spring, take the cut diseased branches and diseased leaves out of the garden and burn them centrally to reduce the source of pathogens for the next year. When cutting off diseased branches and leaves, the scissors can be soaked in Bordeaux mixture at 1:1:100 for 3 to 5 minutes before cutting.