Common diseases of plum blossom and their prevention and treatment

Leaf Roll

Leaf roll is a physiological disease. When ground-planted or potted plum blossoms are under water stress, the leaves on both sides fold inward toward the center, and the entire plum plant appears tired and wilted. In severe cases, a large number of leaves fall off.

The reasons are: on the one hand, it is due to the high temperature and little rain in summer, dry soil, dry air, and excessive light; on the other hand, the plum tree itself has fine fibrous roots and has poor ability to absorb and transport water. In addition, the plum leaves are thin, and the plum plant evaporates water quickly at this time. Overall, the water is deficient, which causes the leaves to curl, especially the "green calyx plum" variety.

The leaf curling phenomenon begins around June , and eases after the rain, with the leaves slightly flattening out. When the weather is good and the water supply is sufficient, the leaf curling appears later, and there will not be a large amount of leaf fall, nor will it affect the differentiation of flower buds.

Prevention and treatment methods

The curling of leaves is due to the special structure and physiological characteristics of the plum blossom itself, as well as the combined effects of adverse climatic factors. To this end, management should be strengthened to ensure that the root system develops well and the tree grows strong, thereby improving its ability to absorb and transport water;

After entering the hot and dry season, strengthen root watering, leaf spraying and environmental sprinkling to create a relatively cool environment for it by humidifying and cooling;

For potted plum blossoms, especially those in shallow pots, and especially for the "green-calyx plum" variety, you can build a shed to provide shade, with the shading degree controlled between 30% and 40% to protect the leaves from curling and falling due to excessive dehydration.

Yellowing disease

Chlorosis is a physiological disease caused by iron deficiency that occurs under alkaline soil conditions. The plum blossoms planted in the ground or in pots in the areas north of the Huaihe River have alkaline soil or culture medium, or long-term use of alkaline water, which causes the roots of the plum plants to be in an alkaline environment for a long time, resulting in necrosis of the nutritional fibrous roots and causing the leaves to turn green and yellow.

Alkali yellowing mainly occurs on the leaves of new branches. The leaves are relatively small, and the veins between the leaves fade to yellow-white and are not very regular, but the veins are still green. The old leaves in the middle and lower parts generally do not turn yellow.

Prevention and treatment methods

The pH value of potting soil or garden soil should be adjusted to below 6.5 . When watering flowers with tap water, let it sit for 3-5 days and add a small amount of ferrous sulfate particles.

Applying alum fertilizer once a month during the growing season can prevent the occurrence of chlorosis. When the leaves show severe yellowing, apply 0.3% ferrous sulfate solution to the roots and spray the leaves with 0.2% solution once every half a month. This two-pronged approach can cause the young leaves to turn yellow and green. For a small number of potted plants, you may also consider using 1% vinegar solution or 0.5% citric acid solution to water the roots.

anthrax

The affected leaves initially develop small brown spots, which later expand into round or oval spots less than 1 cm in size. Those occurring on the leaf margins are mostly semicircular or irregular in shape, gray-brown to gray-white in color, with reddish-brown and dark purple edges, and small black spots on them, arranged in concentric circles. The "Cinnabar-type" plum blossoms are most susceptible to infection, while the "Green-calyx-type" are the most resistant.

Prevention and treatment methods

Remove dead branches and leaves and burn them; starting from mid-April, use 500 times diluted 50% mancozeb wettable powder , or 500 times diluted 50% thiophanate-methyl and carbendazim wettable powder , or 800-1000 times diluted 70% anthrax, thiophanate-methyl wettable powder , spray alternately for 3-4 times.

Gummosis

Gummosis is the main disease of branches and trunks. Diseased branches and trunks turn brown and rot, accompanied by gum flow. The tree gradually weakens, resulting in fewer and thinner branches, poor differentiation of flower buds, and in severe cases, the branches dry up and even the whole plant dies.

Dead branch gummosis usually occurs on perennial branches. It is centered on the lenticels and exudes a fat-like gum liquid that is initially light yellow, translucent, and soft. It then gradually oxidizes and solidifies into brown crystals. In severe cases, the branches above the diseased part will die.

Dry rot type gummosis usually occurs on the main trunk, which appears as water stains at first; then it turns brown and rots. The rotten part gradually turns brown and concave, the bark cracks and curls, and gummosis occurs. In severe cases, the tree becomes weak and the whole plant may even die. It can occur from March to November and is most severe from June to September .

Prevention and treatment methods:

Strengthen water and fertilizer management, and drain stagnant water in time; prevent the invasion of stem-boring pests, and avoid sunburn and frost damage; scrape off the gelatinous matter on the diseased part, apply 3-5 degrees Baume lime sulfur mixture or 0.1% mercuric chloride water for disinfection; or apply 50 times diluted 70% thiophanate-methyl and 50% carbendazim wettable powder to the wound.

Plaster disease

The plaster disease forms large round or oval gray-brown spots on the bark of branches and trunks, which look like flat plasters. Cracks appear in the later stage. The plaster-shaped spots on the twigs are light gray and circle around the twigs. They are later separated from the twigs and sheathed around the twigs. This disease affects the normal growth of the plant, weakens the tree's vigor, and in severe cases the tree gradually becomes weak and dies. It can occur throughout the year, with the highest concentration in summer. Weak trees in humid areas with dense crowns are prone to the disease, and scale insects are the main transmission vector.

Prevention and treatment methods

Provide ventilation and light, dig ditches for drainage; eliminate scale insects and reduce the spread of media; scrape off the diseased parts and burn them after the leaves fall in late autumn and before the leaves sprout in spring, and apply 3-5 degrees of Baume lime sulfur mixture; for a small number of potted plants, scrape off the lesions when they have leaves. Apply Daconil cream ointment.

Soil pollution

Sooty mold is caused by the piercing and sucking damage of aphids, scale insects, etc., and their secretions ——“Honeydew” can easily induce sooty mold disease under relatively humid conditions.

It manifests as a layer of black soot on the leaves, trunks and branches, which seriously affects the normal photosynthesis of the plum leaves, resulting in poor plant growth and inability to bud and bloom normally.

Prevention and treatment methods

If aphids appear in the spring, spray them with 2000 times diluted 10% imidacloprid wettable powder in time ; if scale insects appear, spray them with 2000 times diluted 25% cypermethrin wettable powder ; spray the plants with 800 times diluted 70% thiophanate-methyl wettable powder or polysulfide suspension once every 15 days .

Root cancer

Root cancer is caused by soil root cancer bacteria invading through seedling wounds, and often occurs at the root neck and grafting site, and sometimes also on the trunk and branches. Spherical or oblate tumors grow in the affected area. They are milky white or flesh-colored at first and relatively soft. Later, they become hard, lignified and brown in color. The surface is rough, uneven and cracked. After the plum plant is infected, the root system develops poorly, the above-ground part grows slowly, the tree becomes weak, and flower bud differentiation is affected. In severe cases, the leaves turn yellow and fall off, and even the whole plant dies.

Prevention and treatment methods:

Purchase asymptomatic plum seedlings from epidemic areas and disinfect them before planting. You can soak them in 2000 times 72% agricultural streptomycin sulfate for 30 minutes; or use "anti-root cancer agent" No. Ⅰ or No. Ⅲ, add 1-2 times water and mix well, and dip the roots for 20 minutes before planting , which has a better preventive effect;

If you cannot bear to discard a large plant, you can use a sharp knife to cut out the cancerous part, then apply lime milk or iodine solution ( 50 parts methanol, 25 parts glacial acetic acid, 5 parts iodine tablets ) to the wound, and then maintain it separately.