Why do chrysanthemum leaves turn black?

1. Reasons

During the growth process of the plant, it is often attacked by diseases, which causes various problems. The blackening of chrysanthemum leaves is also a disaster caused by disease, which is caused by black spot disease.

Septoria chrysanthemi attacks the leaves of chrysanthemums and causes lesions, causing the leaves to turn black. In the early stage of the disease, green or purple-brown spots will appear on the leaves of chrysanthemum. These spots have different shapes, including round, oval and even irregular. Their diameter is five to ten millimeters and they are very tiny. The size and color of the spots are related to the variety of chrysanthemum.

Multiple small dots gather together to form large spots. At the late stage of the disease, the color of the spots will turn light gray, and many less obvious small dots will appear. The leaves will begin to wither from bottom to top, but will not fall off. When the disease is serious, there may be only two or three intact green leaves left on a chrysanthemum.

2. Prevention and treatment

1. First of all, if you find leaves that are starting to turn black, you should remove them immediately. If it is winter, the diseased leaves should be destroyed. Do not water or reduce watering when it is cloudy or raining. Be sure not to wet the flowers and do not let the flowerpots be too wet. New flower soil should be replaced every year.

2. Control the fertilizer well, and distribute nitrogen, phosphorus and potassium fertilizers appropriately. Do not let the flowers grow too wildly. If there is too much water in the pot, drain it out in time so that the flowers can thrive and enhance their immunity against diseases.

3. During this period, you can spray the solution. You can go to the market to buy 600 to 800 times diluted 75% thiophanate-methyl, 500 to 600 times diluted 65% mancozeb, or 1% Bordeaux mixture. Spray once every seven to ten days, and only need to spray three to four times to reduce the chance of germs remaining.

4. When buying chrysanthemums, it is best to choose varieties with strong disease resistance. The soil should be turned over and changed frequently. Sand and nutrient soil can be added to the soil. The flower pots, plants, and soil should be cleaned frequently. If you want to transplant the plant, choose branches with leaves that are not diseased and very green.