Cause of death of rhododendron and its control

Rhododendron, there are many common diseases and insect pests. The author has cultivated flowers for many years and can be summed up into eight reasons from practice.

I. Diseases

Black spot is the main disease of rhododendron. The disease is more serious from June to August, and it is the most serious when the temperature is 25 ℃ ~ 32 ℃. When the temperature is below 10 ℃, the disease can stop spreading. After the onset of the disease, the leaves formed black spots and gradually dried up and fell off. This is the main cause of death of cuckoos.

Prevention and treatment: 1. Burn the diseased leaves. 2. Drug prevention and treatment. ① sprayed leaves with 50% wettable carbendazim 600 × 800 times solution or carbendazim, the effective rate was more than 95%; ② was sprayed with 600 × aluminum ethyl phosphate solution. The three drugs were sprayed every 7 days for a total of 3 times and 5 times, with an effective rate of 100%.

II. Insect pests

The main pests of rhododendron are red spider, pink scale and short beard mite, which occur from May to October. After the injury, the leaves appeared brown-red spots, which destroyed the metabolic function, and the leaves fell off, resulting in death.

Prevention and control: 1, to ensure ventilation and cool temperature. 2. Drug prevention and treatment. ① uses 50% dimethoate emulsion 1200 to 1400 times, spray 3 times 4 times in a row, spray once every 7 days, and the effective rate is 100%. Spray with 50% dichlorvos emulsion 1800-2000 times in succession for 3 times, and the effect is up to 100%. ② is sprayed with 50% phosphorus trisulfide emulsion 3000-4000 times, the leaf surface and back should be sprayed. ③ was sprayed with 2000 times of dicofol, and the effective rate was 100%. Spray should seize the opportunity, targeted prevention and control, in order to achieve satisfactory results.

III. Soil damage

Apart from diseases and insect pests, cuckoo deaths are mainly caused by soil pests.

1. Basinization of basin soil. The alkalization of potted soil will lead to rotten roots, yellow leaves, shedding and death. Prevention and control methods: first, irrigate 0.1% ferrous sulfate solution, once a week, 4 times 5 times, can be cured; second, change soil, the pH value is between 6-6.5; third, pour 0.1% concentration of sugar water or retting fruit water; fourth, regularly determine the pH of basin soil, if alkaline, you should immediately change soil or pour ferrous sulfate liquid and so on.

2. Acidification of basin soil. Acidification of basin soil will lead to plant death within 7-10 days. Prevention and control methods: 1. Immediately change the basin soil, keep clean, do not casually put dirt and pulp in the basin; 2. It is necessary to loosen the soil regularly, keep the soil well ventilated, measure the pH value regularly, and adjust the basin soil in time. Do not drop salt water and cooking oil into the basin, and do not use washing water to wash fish and water to water flowers. if there is the above situation, it is better to replace the pot soil in time.

IV. Fertilizer damage

Cuckoos are afraid of thick fertilizer and raw fat. First, they are afraid of human feces and urine, rotten eggs, dead animals and so on. It is true that these fertilizers are good fertilizers, but after use, once fermented, they will burn roots, rot roots and cause death. Fertilizer must be fermented and ripened and mixed with water 10-20 times before it can be applied. It should be less and lighter each time. It is better to apply fertilizer from February to May; second, it is afraid of applying fertilizer at high temperature, and the root is easy to rot after application. Cuckoo fertilization is generally in spring and autumn, and it is best not to apply fertilizer in July and August in summer; third, in addition to organic fertilizer, it is sometimes possible to apply appropriate amount of inorganic fertilizer, but the proportion should be used in accordance with the instructions, and it should be light and not dense.

V. Water damage

Cuckoos can also be killed by water. After 4 or 6 days of stagnant water in the basin, its roots will suffocate and die of hypoxia, and the leaves and branches will wither. If the water holding capacity of basin soil is less than 18%, it is bound to die in about 20 days. Watering should be appropriate and keep 50% to 60% moisture in the basin soil. Water once or twice a day in summer and once every 4 or 5 days in winter to keep the basin soil moist. To often loosen the soil, so that the basin soil loose and breathable, then dry drainage, so that the root system grows well.

VI. Root damage

The roots of cuckoos can grow into a mass in a suitable growth environment, and if they do not turn the pot and change the soil for two years, the roots will not be able to absorb nutrients and water, resulting in death. Therefore, the roots should be cut every autumn and winter to facilitate the growth of new roots. Root pruning every year, in order to promote the growth of the plant, flowering more, flowering large. It can also be changed from a small basin to a large basin for maintenance.