Common Diseases of Chrysanthemums and Their Prevention
This article brings you knowledge about chrysanthemums from the perspective of a floral clinic, including common diseases of chrysanthemums and their prevention. Next, our site editor will introduce them to you.
In deep autumn, various chrysanthemums bloom. Chrysanthemums are easy to cultivate, but like other plants, they also have many common diseases. The common diseases of chrysanthemums include powdery mildew, black spot disease, stem rot, and mosaic virus. So, how do we diagnose and prevent them?
Powdery Mildew
Symptoms: Lesion areas show white powdery substances, commonly found on leaves, petioles, etc., sometimes young stems, peduncles, and flower buds can also be affected. Initially, the powdery substance is mainly on the front of the leaves. When conditions are favorable, the entire leaf is covered with white powdery substance, and black spots appear later. In severe cases, leaves wither and curl, the plant becomes dwarfish, and petals are malformed or do not bloom.
Prevention:
(1) Timely remove diseased leaves and residues and incinerate them.
(2) Pay attention to ventilation and reduce humidity when watering, and fertilize reasonably.
(3) Before the onset of the disease, from mid-April to mid-August, alternately spray 80% mancozeb 800 times liquid and 50% thiophanate-methyl wettable powder 800-1000 times liquid, twice a month.
(4) During the outbreak, spray 20% diniconazole 600-800 times liquid or 50% carbendazim 500 times liquid, spray every 5-7 days, for 2-3 times.
Black Spot Disease
Symptoms: Initially, round or oval purplish-brown spots of varying sizes appear on the upper surface of the leaves, then the color gradually turns black to dark brown, with spot diameters of 2-10 millimeters; in the later stage, the edges of the spots are dark brown, the center turns grayish-brown to light gray, and small black spots appear. In severe cases, spots connect with each other, causing the entire leaf to turn black and dry, hanging on the stem.
Prevention:
(1) Diseased leaves should be removed immediately.
(2) Implement a two-year or more crop rotation for field chrysanthemums, and pot-grown chrysanthemums need to be changed to new soil every year.
(3) Choose healthy mother plants for propagation and soak them in 50% thiophanate-methyl 1000 times liquid or 80% mancozeb 600 times liquid for 1-2 minutes.
(4) In winter, cut and burn the remaining stems and leaves on the ground, and deeply turn the soil to bury them.
(5) In early April, spray 1% Bordeaux mixture or 80% mancozeb 600-800 times liquid to prevent disease.
(6) During the outbreak, spray 75% chlorothalonil 700 times liquid or 40% tebuconazole 800-1000 times liquid, spray every 7-10 days, for 3-4 times.
Stem Rot Disease
Symptoms: When seedlings are infected, the base of the diseased seedlings initially appears watery, then turns brown, causing seedling death. When mature plants are infected, leaves, buds, and flowers gradually wither, the main stem remains green for a long time, and the infected base shows long, wrinkled brown spots, causing stem withering and root rot, leading to the death of the entire plant.
Prevention:
(1) Soil and flowerpots should be disinfected with 2-4% formalin or 50% captan.
(2) Avoid strong sunlight during the seedling stage, control the amount of watering, and drain water promptly after rain.
(3) Control planting density, fertilize reasonably, and do not overuse nitrogen fertilizer.
(4) Avoid injuring seedlings during management.
(5) Diseased plants should be removed and incinerated in time.
(6) Applying 0.1% potassium sulfate or 100ppm boric acid externally can enhance the plant's resistance to diseases.
(7) During the outbreak, mix and spray 36% methyl thiophanate suspension 800 times liquid and 40% carbendazim 1000 times liquid.
(8) Use a mixture of 50% thiophanate-methyl and water at a ratio of 1:10 for root irrigation, which has good effects.
Mosaic Virus
Symptoms: Diseased leaves show unevenly distributed necrotic spots of varying sizes, serious cases show brown necrotic spots, causing the entire leaf to necrotize and fall off.
Prevention:
(1) Do not use virus-infected plants as propagation material to cut off the pathogen at the source.
(2) After selecting propagation material, it should be heat-treated.
(3) Disinfect the operating tools, avoid injuring the plants, and remove weeds and other hosts.
(4) Completely control aphids, thrips, leafhoppers, and other virus-carrying pests to prevent virus transmission.
(5) Diseased plants should be removed and incinerated in time.
(6) Avoid planting too densely to ensure good ventilation and light, cultivate strong seedlings, and enhance the plant's resistance to diseases.
(7) Using shoot tip culture to eliminate the virus is a currently good method.
The above () introduces the full content of common diseases of chrysanthemums and their prevention, hoping it is helpful to green plant enthusiasts!