Leaf spot is a kind of true chrysanthemum disease, which usually occurs in the period of cold weather at the end of autumn, especially in the northern area where the temperature is not kept in time.
The initial symptom is that the leaves appear light yellow or red yellow spots, and the spots gradually expand, in a round or oval shape. If the environment is relatively wet, black particles will appear on the spots, which is the conidia organ of the pathogen.
In the later stage, the disease became worse, and the leaves gradually dried up until they fell off.
The best way to prevent and control leaf spot is to do a good job of cold prevention. When the wind cools down after autumn, we should take protective measures to the hanging lamp Fusang, place it in a place with high environmental temperature, and maintain a certain temperature.
On the basis of keeping warm, spraying 500-800 times of zinc or 1500 times of ammonium in time can also have a good control effect.
Stem rot is a kind of fungal disease with serious harm and wide range. It usually occurs in rainy season and in high temperature and rainy conditions.
The pathogen will infect from the root and stem junction of Hibiscus davidianus. The initial symptoms are not obvious. The cortex of the affected part is shrunk and slightly dark brown, but the subcutaneous tissue has begun to rot.
After that, the yellow brown withered spots gradually spread inward, the leaves dried up and fell off, and the plants would wither and die after the disease spots around the stem for a week.
The key to prevent stem rot is to prevent rainstorm from washing the boughs of Fusarium davidianum for a long time, and to smear the boughs of Fusarium davidianum with 200-500 times liquid tobuzin every 10 days before and after the rainy season.
The root knot nematode disease mainly occurs in the branches and leaves of Fusarium mori. At the beginning, the growth of the leaves is weak, and the edge of the leaves appears red brown spots. At the later stage, the disease spots gradually expand inward, and the leaves are dry and fall off.
If we observe the underground part of Hibiscus davidianus, we will find that there are large and small tumors between the roots of the plant, which are smooth at the initial stage, rough brown at the later stage, and pear shaped female nematodes with the size of needle tip inside.
The prevention and treatment of this disease is difficult. If the number of plants is small, change the soil. After a long time of exposure, the believers can discard the old soil.
If there are many plants, aldicarb granules can be applied, and 0.5g can be buried in a 5-inch basin.
