International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.2, 63-73 http://ecoevopublisher.com/index.php/ijmec 64 2 Overview of Common Pests and Diseases in Hangbaiju 2.1 Major diseases Chrysanthemum morifoliumis threatened by a variety of fungal diseases during cultivation. Powdery mildew is a typical airborne disease, and its typical symptoms are the formation of white powdery spots on leaves and stems. The disease is particularly rampant under warm and dry conditions, seriously affecting the normal growth and development of plants by interfering with photosynthesis and inducing leaf deformities. Fusarium oxysporum is caused by the soil-borne pathogen Fusarium oxysporum, which invades the root system and destroys the vascular system, resulting in characteristic leaf yellowing and wilting symptoms. The pathogen can be spread through soil, irrigation water and diseased residues, causing dwarfing or even death of plants in the field. Studies have shown that biochar improvement can effectively reduce the number of Fusarium oxysporum in the soil (Chen et al., 2018). Leaf spot is another important disease with a complex pathogenic composition, including Epicoccum sorghinum and Nigrospora oryzae. The disease initially manifests as scattered necrotic spots, which merge into large brown-black patches as the disease progresses, eventually causing the leaves to curl and necrotize. High temperature and high humidity environments significantly increase the severity of the disease, posing a serious threat to yield (Chen et al., 2020; Sha et al., 2023). 2.2 Major pests During the cultivation of Chrysanthemum morifolium, two typical pests often attack it. Aphids, as a representative of piercing-sucking pests, continuously suck the plant sap, causing leaf curling and growth stagnation. At the same time, as a virus transmission medium, they aggravate the degree of damage (Ji-Shuang, 2007). Its population grows exponentially under 15~25 ℃ conditions, with explosive damage characteristics. Red spiders show a different damage pattern. This type of tiny mite pest destroys leaf mesophyll cells through its mouth needle, causing characteristic chlorotic spots, and in severe cases, causing leaves to scorch and fall off (Srikumar et al., 2015). It is worth noting that this pest has dual damage characteristics: in addition to damage to the aboveground part, its root infection can form typical root nodules, significantly inhibiting the absorption of water and nutrients by seedlings, causing plant development stunting. A dry environment above 28℃ is particularly conducive to the rapid proliferation of its population, and the damage is particularly prominent in facility cultivation. 2.3 Damage mechanisms of pests and diseases Various pests and diseases interfere with the normal physiological functions of Chrysanthemum morifolium through different pathways. After Fusarium oxysporum infects the plant, it selectively destroys the vascular system, blocks the transport of water and mineral nutrients, and eventually causes systemic wilting of the plant. Leaf spot disease directly damages the mesophyll tissue, significantly reducing the chlorophyll content and photosynthetic efficiency. Field observations showed that the affected plants showed typical apical wilting (Figure 1A) and leaf yellowing (Figure 1B), and the lesions showed characteristic brown necrosis (Figure 1C, Figure 1D), which directly reflected the severity of the disease. The harm of piercing-sucking pests should not be ignored. Aphids not only cause malnutrition of plants by continuously sucking phloem sap, but also act as virus carriers to cause complex infection. Red spiders aggravate the water imbalance and metabolic disorder of plants by destroying the mesophyll cell structure. These biological stress factors work together to inhibit the growth and development of Chrysanthemum morifoliumfrom multiple levels, ultimately leading to a significant decrease in yield and quality (Chen et al., 2020; Sha et al., 2023). Establishing a targeted prevention and control system is of great significance to ensuring the sustainable development of the Chrysanthemum morifoliumindustry. 3 Biological Control Technologies for Hangbaiju Pests and Diseases 3.1 Microbial control Microbial control, as an important means of green control of Chrysanthemum morifolium diseases, has shown unique advantages. Bacillus siamensis D65 showed significant inhibitory effects on Nigrospora oryzae, the
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