Spruce is transplanted well in spring. Why do leaves turn yellow and dry in autumn?

This phenomenon has also been found in the process of planting and transplanting Picea koraiensis in Huanren Hexing Nursery Professional Cooperative in Liaoning Province over the years. There may be two situations in your question, one is that the tree is fake, and the other is that the tree is sick. The first case may be that the roots of trees are not well sealed when transplanted in spring, or there are holes under the roots, which leads to the slow death of trees. In the second case, I think the white and yellow side branch you mentioned is probably the leaf rust of Picea koraiensis. See if it meets the following symptoms: generally, in late June, pale yellow spots appear on the young leaves of Picea koraiensis, on which yellowish-brown to dark brown dots are arranged in rows, that is, the sex spore apparatus of pathogenic bacteria, and there are pale yellow beads at the top of the dots. A few days later, between or opposite the sexual spore apparatus, an oval or long rust spore apparatus with orange microprotrusion is produced. The diseased leaves gradually turn pale yellow and orange rust spores are densely distributed. The forest with serious diseases shows the yellow crown in the distance. When the rust spore apparatus is mature, the coating film breaks one after another, spreading yellow powdery rust spores, and the diseased leaves dry up and fall off in September-65438+1October.

Spruce leaf rust is mainly distributed in Heilongjiang, Jilin, Liaoning, Yunnan, Sichuan, Hebei, Shanxi, Shandong, Taiwan Province and Qinghai provinces. Picea crassifolia seedlings aged 1 ~ 4 years in natural young spruce forests, artificial young spruce forests and nurseries are prone to this disease. The seriously ill plants in the young forest delayed germination or did not germinate the next year, and the branch length was shortened year by year, and the growth declined.

If the symptoms I described above are met, the main pathogen is Chrysomyxa rhododendri De Bary, a rust fungus with a long cycle life history. Parasitic on the new leaves of Picea koraiensis in the stage of sexual spore apparatus and rust spore apparatus, and occasionally on Picea ichthyoides. Summer spore pile and winter spore pile are parasitic on the leaves of Rhododendron dahuricum.

The sex spore organ is born under the cortex of tender leaves, with yellow-brown hills, with a diameter of 0. 15 ~ 0.24 mm and a height of 0. 1 ~ 0. 13 mm. It contains fertilized filaments and sex spores, and its top secretes nectar. Sex spores are rectangular. Colorless, the size is 5.1~ 8.3 μ m× 3.1~ 4.6 μ m.

The rust spore organ is orange-yellow, rectangular and cylindrical, with a length of 0.5 ~ 1. 1 mm, a width of 0.3 ~ 0.5 mm and a height of 0.8 ~ 1.2 mm. The rust spore is oval and orange-yellow, with a size of 20.3 ~ 27.5 μ m×/kloc-. There are warts on the surface. Under the electron microscope, the surface can be divided into wart area and smooth area. The wart is tower-shaped and flat-topped, and the smooth area is U-shaped, accounting for about 1/4 ~ 1/3 of the spore surface area.

The summer spore pile is scattered or densely born under the epidermis of the leaf back, and then exposed, with a spire shape and a capsule. The base has a diameter of 0.3 ~ 1.5 mm and a height of 1.2 ~ 2.0 mm. Summer spores are ovoid, orange, beaded and warty, and the size is 21.2 ~ 28.7 μ m×17.0 ~ 21.5 μ m.

The winter spore pile is oblate, exposed under the leaf epidermis after birth, brownish red, with a diameter of 0.3 ~ 0.5 mm, and some of them are connected to form a large winter spore pile. The winter spores are unicellular, colorless and smooth, short cylindrical and beaded, with the size of10 ~ 20μ m×10 ~16μ m. The winter spore chains are 40 ~ 80μ m long and loosely connected into a pile.

The basidiospores are bright yellow, irregular and round, with short flat-topped warts on the surface, and the density is uneven, with the size of 22.0 ~ 24.7 μ m×16 ~ 21μ m.

Occurrence law

1. infection cycle: the pathogen overwinters on the leaves of rhododendron dahuricum, an evergreen shrub, and there are dark brown spots on the surface of the diseased leaves, which gradually develop in the following spring. From late May to early June, a slightly raised dark brown-red winter spore pile was formed. Winter spores mature in the middle and late June and germinate under suitable humidity conditions to produce basidiospores. Basidiospores spread with the wind and infected the young leaves of spruce. Spruce showed symptoms in late June or early July. From mid-July to late August, the rust spore apparatus gradually matured and ruptured, releasing rust spores. Rust spores spread with the wind and infected Rhododendron dahuricum. A pile of orange summer spores are produced on the back of the leaves, and when the summer spores mature, they fly away and infect rhododendrons repeatedly. At the end of autumn, the hyphae in the summer spore stage overwinter.

2. Epidemic situation: The pathogen was first discovered in China 1928 Fenghuang Mountain, Liaoning Province, and now it is distributed in China 10 provinces, but it has not caused the epidemic of spruce leaf rust. Due to the massive logging of broad-leaved Korean pine forest, the proportion of natural regeneration and artificial regeneration of the host Picea koraiensis has greatly increased, and the intermediate host Rhododendron Hinggan has proliferated and spread all over the mountain. Decades have passed, and a large number of pathogenic bacteria have accumulated, so it has the basic conditions for the epidemic of rust. Finally, under suitable meteorological conditions, spruce leaf rust further developed and spread.

3. Relationship between disease and light: Young and strong natural Picea koraiensis forests, especially those located in the plains and river valleys on both sides of the highway, which have been exposed to light for a long time, are seriously ill, which may be that the negative Picea koraiensis species are not adapted to long sunshine, resulting in weakened disease resistance.

4. Relationship between diseases and stand types: Pure spruce forest is heavier than mixed spruce forest. Generally, under the same site conditions, young forest is heavier than mature forest.

Picea crassifolia has stronger disease resistance than Picea koraiensis, and natural Picea rarely gets sick.

Prevention and cure method

1. Eliminate intermediate hosts and reduce sources of infection: uproot Rhododendron dahuricum in time after flowering, especially near the nursery.

2. Create a mixed forest of spruce and other tree species.

3. Using plastic film as an arch shed on the seedbed can directly block the infection of pathogenic bacteria, and removing the arch shed after the infection period can get good disease prevention effect.

4. During the infection period, the nursery and artificial young forest should be sprayed with chemicals in time, which can be sprayed once every 10 ~ 15 days and continuously for 2 ~ 3 times.

I hope my answer is helpful to you.