The mystery of yellow spots on chrysanthemum leaves: analysis of causes and control methods.

Causes and Control Methods of Yellow Spots on Chrysanthemum LeavesDuring the cultivation of chrysanthemums, many flower enthusiasts encounter a problem: sudden appearance of yellow spots on chrysanthemum leaves. This not only affects the appearance of chrysanthemums but may also impact their growth. What exactly causes the yellow spots on chrysanthemum leaves? How should we prevent and treat them? This article will reveal them one by one.Causes of Yellow Spots on Chrysanthemum Leaves1. Disease InfectionThe yellow spots on chrysanthemum leaves are likely caused by disease infections, such as downy mildew, powdery mildew, and anthracnose. These diseases usually occur more easily in high temperature and humidity environments.2. Pest InfestationPest infestation is also one of the reasons for yellow spots on chrysanthemum leaves. Common pests include aphids, red spiders, and scale insects, which extract the sap from the leaves, causing spots to appear.3. MalnutritionYellow spots on chrysanthemum leaves may also be related to factors such as soil and fertilizer. Issues like compacted soil, insufficient water, lack of fertilizer, or improper fertilization can lead to malnutrition in the leaves, resulting in spots.4. Environmental FactorsChrysanthemums are adaptable to the environment, but under extreme conditions, such as very high or low temperatures, or severe air pollution, yellow spots may appear on the leaves.Control Methods of Yellow Spots on Chrysanthemum Leaves1. Preventive Measures(1) Maintain ventilation and light: During the growth of chrysanthemums, it is necessary to maintain good ventilation and lighting conditions to prevent disease breeding.(2) Reasonable fertilization: Apply nitrogen, phosphorus, potassium, and other fertilizers as needed based on the growth requirements of chrysanthemums to ensure balanced nutrition.(3) Control watering: Watering should be moderate to avoid waterlogging and prevent root rot.2. Treatment Measures(1) Disease control: Once diseases are detected, promptly remove the diseased leaves and use appropriate pesticides for prevention and treatment. For example, use a 75% chlorothalonil wettable powder 1000 times liquid spray for downy mildew, and a 25% triazole wettable powder 1000 times liquid spray for powdery mildew.(2) Pest control: Once pests are detected, use pesticides for control. For example, use a 10% imidacloprid wettable powder 1500 times liquid spray for aphids, and a 1.8% abamectin emulsifiable oil 2000 times liquid spray for red spiders.(3) Environmental improvement: Improve the growing environment of chrysanthemums, such as adjusting temperature, humidity, and lighting, to reduce the incidence of diseases.The yellow spots on chrysanthemum leaves may be caused by various reasons, including diseases, pests, malnutrition, or environmental factors. Understanding the causes of the spots enables us to take effective preventive and treatment measures to ensure the healthy growth of chrysanthemums. It is hoped that this article will be helpful to the majority of chrysanthemum enthusiasts.References:[1] Zhang Lihua, Liu Chunyan. Chrysanthemum Disease and Pest Control Techniques [J]. Farmers' Science and Technology, 2018(10): 36-37.[2] Zhao Chunli, Wang Lina, Liu Xiaohui. Chrysanthemum Cultivation Techniques and Disease and Pest Control [J]. Plant Protection, 2017, 43(2): 52-54.