Stem blight:
It is caused by botrytis cinerea in Japp.
Symptoms: The leaves, branches and trunks of cedar are all harmed by this disease.
1. In the early stage of dead leaf disease, on the spring shoots that germinated that year, new needles began to turn yellow from the tip, and soon the whole cluster of needles also turned yellow, and then the needles gathered and hung on the tender branches. Biennial needles can also be infected and die from the top to the base.
2. Dead buds are damaged and die. A tree can have more than one tip infected. The new buds droop like water stains first, and then turn into yellow-brown dead branches, which can expand downward. Disease spots can be formed at the branches of branches, which usually sink and flow out light gray or light blue turpentine, and the disease spots can be continuously expanded. When the lesion surrounds the trunk, the branches above the lesion die. In the later stage, black spots can be seen on the diseased spots, that is, conidia of the pathogen.
3. The needles of the stem rot tree gradually turn yellow, and then the whole tree dies. Careful examination revealed that the stem base was diseased, and the diseased part of the lesion could extend to the root. The cortex of the affected area turns black and decays, and the xylem changes color when the bark of the affected area peels off.
Extended data:
Causes and treatment of cedar dying;
1, moisture-drought and water accumulation
Cedar is a drought-tolerant tree species, but excessive soil drying is not good for the growth of Cedar, which will make its leaves yellow and lifeless. Many cedars are planted in cement-hardened platforms, flower beds, or tree pools, leaving less than half a square meter and lacking water.
Too much watering, or too much rain, or low planting terrain, leads to water accumulation, which makes the soil in a state of excessive humidity for a long time, resulting in rotten roots of Taxodium ascendens needles.
The suitable soil moisture should be between 15%-30% and lower than 10%. Cedar plants grow poorly and wither easily. More than 35%, cedar is easy to rot and die. Water those who are short of water due to limited space often, and dig deep into the drainage ditch to remove excess water for those who are prone to water accumulation.
2. Nutrients-Limited space and insufficient nutrition
Many delicate cedars have been planted in flower beds or hardened small spaces since childhood. After more than ten or twenty years of growth, there is a serious shortage of underground nutrition space, which limits the growth of cedar roots and the absorption of nutrients and water. This leads to thinning, yellowing and dead branches of cedar needles.
For this reason, if it is impossible to expand the growth space of cedar, we can apply organic fertilizer in spring and autumn, and dig a deep ditch with a depth of 30-40 cm on the side as close as possible to the edge of the crown. Organic fertilizer should be put in the ditch, mixed with soil and then watered. Usually, foliar fertilizers such as trace elements, amino acids and regulators are sprayed on the leaves.
3. Pathogens-Stem Blight and Gray Mold
These two diseases occur in spring and summer, which mainly harm needles, twigs and biennial branchlets. This phenomenon is higher when the rainy season is longer and cedar has a wound.
Control method: 40% carbendazim 1000 times solution and 70% zineb 800 times solution were sprayed on the leaves, branches and branches of Cedar in April-May, with mild symptoms 1-2 times and severe symptoms once every 15 days.
The problem of cedar is often not caused by one factor, but by the comprehensive influence of several reasons. To treat the problem differently, only by finding the main factors that lead to the problem can we solve the problem with a clear aim.