1. Symptoms

　　It primarily absorbs the plant's sap, causing grayish-white spots on the leaves. In severe cases, it leads to yellowing and leaf drop. New shoot growth is poor, and the tree's vigor weakens.

　　2. Disease pattern

　　High temperatures from June to August are particularly harmful during droughts, but heavy rains and rainy weather cause less damage.

　　3. Prevention and control methods

　　Remove dead branches and fallen leaves in winter to kill overwintering adults. When damage begins in March, spray with 10% Tianhuangxing EC at 1000 times dilution, 7051 insecticide (Michengling) at 3000 times dilution, or pyridazine (Xuzhitong) at 1000 times dilution.

　　Azaleas: How to grow azaleas well in the north? Here are three tips.

　　1. Symptoms

　　Gray mold occurs on the leaves and flowers of azaleas. Freezing damage is a common predisposing factor for leaf infection. In spring, the flowers of azaleas cultivated indoors and outdoors are frequently infected with gray mold. In the early stages, necrotic spots appear on the petals, rapidly expanding and merging to form large lesions. Under high humidity conditions, a large amount of gray conidia are produced on the diseased areas, hence the name gray mold.

　　2. Pathogen

　　Botrytis cinerea belongs to the Deuteromycetes. The fruiting bodies of the pathogen arise from mycelia or sclerotia. Conidiophores are clustered, gray, later turning brown, and conidia are oval. Its sexual generation, Botrytis fusiforme, belongs to the Ascomycetes.

　　3. Prevention and control measures

　　①Strengthen cultivation management to prevent frost damage and reduce the occurrence of diseases.

　　② When cultivating azaleas indoors, pay attention to ventilation and avoid excessive humidity.

　　③ In daily management, diseased leaves and flowers should be removed and burned in a timely manner.

　　④ If necessary, spray with 50% chlornitramine at a dilution of 1000 times or 50% carbendazim wettable powder at a dilution of 1000 times for prevention and control.

　　1. Symptoms

　　Both adult and nymphal insects congregate on the underside of leaves, sucking sap. Affected leaves develop a black, sticky substance on the underside that resembles splattered sap. This characteristic easily distinguishes it from other piercing-sucking pests. The entire underside of the affected leaf turns rust-yellow, while the upper surface develops many pale white spots. In severe cases, the spots merge, eventually causing the entire leaf to lose its green color, appearing pale from a distance. Premature leaf drop occurs, and flower buds no longer form.

　　2. Morphological characteristics

　　The adult is about 3.5 mm long, flat, and dark brown. The antennae are filiform and four-segmented. The pronotum has a longitudinal ridge in the center, extending backward into a leaf-like projection, while the sides of the pronotum protrude outwards in feather-like shapes. The forewings are slightly rectangular. Consistent reticulate patterns are present on the forewings, the sides of the pronotum, and the leaf-like projections on the dorsal surface. When at rest, the forewings are folded, and when viewed from above, the entire insect resembles an "X" shape composed of multiple wings. The eggs are oblong, curved at one end, and about 0.6 mm long. Initially pale green and translucent, they later turn pale yellow. The larvae are milky white upon hatching, gradually turning dark brown, and are about 1.9 mm long. By the third instar, wing buds are distinct, and the insect resembles the adult in appearance, with prominent conical spines on both sides of the pronotum, mesothorax, and abdominal segments 3-8.

　　3. Life history and habits

　　The insect has 4-5 generations per year in the Yangtze River basin and 3-4 generations in North China. Adults overwinter in dead branches, fallen leaves, weeds, bark cracks, and crevices in soil and rocks. Overwintering adults become active in early to mid-April, congregating on the undersides of leaves to feed and lay eggs. Eggs are laid inside leaf tissue, covered with a yellowish-brown gelatinous substance, and the incubation period lasts about half a month. Newly hatched nymphs mostly cluster on both sides of the midrib, causing damage. Nymphs molt five times, maturing into adults in about half a month. The first generation of adults emerges in early June, with subsequent generations occurring in late July, early August, and late August/early September, respectively. Due to the long adult and oviposition periods and overlapping generations, different life stages often coexist. Damage is most severe in July and August, with the highest population density in September, and overwintering begins in late October. Adults prefer to be active at noon. The number of eggs laid by each female adult varies depending on the host, ranging from dozens to hundreds. Eggs are laid in batches, with several to dozens of eggs laid next to each other. There is a small black dot with a slight depression in the center on the outside of the egg-laying site.

　　4. Prevention and control methods

　　Thoroughly remove fallen leaves and weeds from potted plants and bonsai gardens during winter. For plants with thicker, rougher stems, apply a whitewash. The most favorable time for chemical control is during the period from the emergence of overwintering adults to the hatching of the first generation of nymphs. Spray with 50% fenitrothion at a dilution of 1000 times, or 40% dimethoate at a dilution of 1000-1500 times, or 10-20% pyrethroids at a dilution of 1000-2000 times, once every 10-15 days, for 2-3 consecutive applications.

　　Azalea: Azalea Propagation Guide (Illustrated)

　　Iron deficiency chlorosis, also known as yellow leaf disease or chlorosis, is a common disease of potted azaleas in various regions.

　　1. Symptoms

　　This disease mostly occurs on tender shoots and new leaves. In the early stages, the leaf tissue between the veins turns pale green and loses its luster, gradually turning yellowish-white, while the veins remain green, giving the green on the leaves a reticulated appearance. Subsequently, the yellowing gradually worsens, and except for the larger veins, the entire leaf turns yellow or yellowish-white. In severe cases, the leaves wither and scorch inward along the leaf and leaf margins.

　　2. Pathogen

　　Iron deficiency chlorosis in azaleas is a physiological disorder primarily caused by iron deficiency in the soil or the inability of iron to be absorbed and utilized, thus affecting chlorophyll synthesis and causing the leaves to turn yellowish-green. Under normal circumstances, the following factors contribute to this: In calcareous alkaline soils, usable soluble ferrous iron is converted into insoluble ferric salts and precipitates, preventing root absorption; frequent watering of potted plants leads to excessive leaching of soluble iron from the soil; in areas with heavy, poorly drained soil or high water tables, root development is affected, normal root physiological activities cannot occur, and the roots' ability to absorb iron is reduced.

　　3. Prevention and control methods

　　Azaleas prefer acidic soil and dislike alkaline soil; avoid planting them in alkaline soil or soil high in calcium . When planting in open ground in gardens, keep them away from cement, brick walls, or areas where lime has been used. Potted azaleas prefer acidic soil; if the soil is too alkaline, replace it with acidic soil. When planting azaleas in nurseries, compost, green manure, or other organic fertilizers can be applied. The organic acids produced in these fertilizers can dissolve insoluble iron in the soil, making it easier for the plant to absorb. Alternatively, ferrous sulfate can be mixed into the fertilizer. The preparation method is: 2.5-3 kg of ferrous sulfate, 5-7.5 kg of oilseed meal, 10-15 kg of manure, and 200-250 kg of water. After mixing, allow it to decompose until it turns black before use. This method is very effective. In alkaline soils, a 0.1-0.2% potassium dihydrogen phosphate solution can be applied. This solution has a pH of 4.7, which can turn alkaline soil into acidic soil, thus treating yellowing of young leaves. Potassium dihydrogen phosphate also contains phosphorus and potassium, which are beneficial for flowering and increasing the number of flowers. Frequent application of ferrous sulfate solution can lead to excessive sulfur and available iron in the soil, causing plant poisoning. A better solution is to mix 0.14 grams of disodium ethylenediaminetetraacetate and 0.1 grams of chemically pure ferrous sulfate in 500 ml of tap water and spray the leaves, covering both the upper and lower surfaces, every 3 days for several applications to achieve good results.

　　1. Symptoms

　　Water-soaked brown spots and soft rot appear on the roots, followed by rotting and peeling. The xylem turns dark brown, and the bark gradually turns grayish-white. This process gradually spreads until the entire bark of the trunk dies, cutting off the transport of nutrients and water. This causes the tender leaves at the top to gradually dry up, and from top to bottom, the branches and leaves wilt, lose water, and dry up, eventually leading to the death of the entire plant.

　　2. Occurrence pattern

　　Root rot is a soil-borne disease caused by Fusarium fungi. It often occurs in the root and stem parts of azaleas because these parts are often damp and lack sunlight, allowing Fusarium fungi, a type of deuteromycete, to be active. Once the fungus invades the cortex, it will soon cause rot.

　　3. Prevention and control methods

　　Fusarium fungi, a type of deuteromycete, survive on plant debris in the soil and can remain infectious for several years if they encounter a suitable host. Alkaline soil, high humidity, and high temperature all promote the development and spread of the disease. Therefore, after diagnosis, dead plants and potting soil should be treated promptly.

　　For nearby plants, soak or rinse the entire plant with 0.1% potassium permanganate solution, and rinse with clean water before potting. The potting soil can be sprayed with 1000 times diluted 70% carbendazim solution beforehand.

　　Attention should be paid to improving site ventilation, increasing sunlight in the morning and evening, applying more potassium fertilizer, and improving disease resistance.

　　Apply a 200-fold dilution of Topsin to the main stem around May each year, once every 7-10 days, for three consecutive times to prevent infection.