Diagnosis of root rot symptoms
Root rot, also known as root rot, mainly damages the roots and causes root cortex to rot. The main symptoms and characteristics are: between the cortex and xylem and inside the cortex are filled with white to light yellow-brown mycelium, and the front edge of the mycelium is fan-shaped Expanding outward, the fresh mycelium layer has a bluish fluorescence in the dark and has a strong mushroom smell. In the later stage of the disease, the cortex of the diseased part is rotten, and the xylem is rotten; in the rainy season or under humid conditions, clusters of honey-yellow mushroom-like objects can be produced at the diseased part or broken roots. For mildly diseased trees, the leaves are small, light in color, leaf margins are curled, and the growth of new shoots is small; for severely diseased trees, germination is late, leaves fall early, branches die, and even the whole plant dies.
Pathogens and occurrence characteristics
Root rot is a higher fungal disease caused by Armillariella tabescens. In addition to invading apple trees, the pathogen can infect more than 300 kinds of fruit trees and forests such as pear trees, peach trees, walnuts, poplars, willows, and pagoda trees. The pathogen mainly overwinters on the diseased plants and the diseased residues in the field with mycelium, and can survive with the diseased residues for many years, and the pathogens die after the diseased residues rot and decompose. The contact of diseased and healthy roots and the movement of diseased residues are the main ways for disease to spread, and the pathogens infect directly or from wounds. The disease mostly occurs in orchards rebuilt from old woodlands, old orchards, riverbanks or ancient tomb cemeteries, and the orchards that have not been planted before are rarely affected.
Prevention and control technology
Prevention of root rot must be given priority, and the key is to pay attention to the previous crops in the orchard; it is also very important to detect diseased trees early and treat them in time.
(1) Pay attention to the previous cropping and soil treatment of the orchard. When building a new orchard, do not choose old forest land, old orchards, river beaches with many trees, ancient tomb cemeteries and other places. If it is necessary to build a garden on such a plot, it is necessary to completely remove tree residues such as stumps, residual roots, and rotten bark, and promote the decay and decomposition of residual tree residues and the death of germs (covering film is closed at high temperature in summer, etc.).
(2) Timely treatment of diseased trees After the diseased tree is found, find the diseased site, completely scrape or remove the diseased tissue, and completely remove the diseased body, and burn it in a concentrated manner; then apply 77% copper calcium sulfate wettable powder 100 to 200 times liquid, or 2.12% copper humic acid aqueous solution, or 1% to 2% copper sulfate solution, or 3 to 5 Baume degrees lime sulfur mixture, or 45% lime sulfur crystal 30 to 50 times liquid, etc., to protect Wound. For mildly diseased trees or when it is difficult to find the diseased site, it can also be directly treated by punching and pouring formalin. Prick a hole with a diameter of 3 cm and a hole depth of 30 to 50 cm every 20 to 30 cm within the range of the canopy orthographic projection, pour 100 to 150 ml of formalin solution 200 times into each hole, and then seal the hole with soil. Can. Note that it is not suitable to irrigate the weak trees and the high temperature season in summer to avoid phytotoxicity.
(3) Other measures After the diseased tree is found, dig a blockade ditch to seal the diseased tree to prevent spreading. Generally, the depth of the ditch is 50-60 cm, and the width of the ditch is 30-40 cm. After the diseased tree is treated, increase the amount of fertilizer and water, control the amount of fruit, replace the root or graft the root in time, and promote the recovery of the tree vigor.
