aphid

　　[Morphology and Risks] Aphids are divided into winged and wingless types. Winged viviparous females have transparent wings and a dark brown body; wingless viviparous females are wingless and have a dark brown body. Additionally, nymphs resemble adults in appearance, are wingless, and pale yellow. Adults and nymphs congregate on the tender shoots of camellias, sucking sap and causing the buds and leaves of the affected camellias to wither, severely impacting their development. The exudate from aphids can cause sooty mold.

　　[Prevention and Control System]

　　① During the peak period of aphid infestation, spray the camellia plants with a 2000-fold dilution of 50% phosphatidylcholine emulsion or a 1000-fold dilution of 50% dimethoate emulsion.

　　Spray once every 3-5 days, for a total of 3 times, to kill aphids. ② Soak 0.5 kg of tobacco residue and 0.25 kg of quicklime in 10-15 liters of water for 24 hours and 3 days. Filter out the residue and use the solution for spraying. The results are good.

　　Scale insects

　　[Habits and Risks] Camellias are susceptible to several types of scale insects, with the most serious being the cottony cushion scale, red wax scale, and chaff scale. Scale insects lay a large number of eggs annually, with each female laying up to a thousand eggs, and there are 3-5 generations per year. Most overwinter as fertilized females on the branches and leaves, and begin laying eggs and causing damage in March of the following year, primarily concentrating on young branches and leaves to absorb sap. Affected leaves turn from green to grayish-green, and finally to yellow. In severe cases, the branches and leaves are covered with scale insects, causing the entire plant to wither and die. Their exudate can induce sooty mold.

　　【Control Methods】① Manual Control: These insects mostly congregate in groups. When their numbers are low during the life cycle, they can be directly crushed on the branches and leaves. ② Chemical Control: Take advantage of the weakened resistance of newly hatched nymphs and apply pesticides at the right time. Adults have a waxy coating, making control less effective. Commonly used pesticides include a pine resin mixture made by boiling pine resin and caustic soda in water. This solution is dark brown and mainly contains excessive free alkali and pine resin soap, which has a strong corrosive effect on the waxy coating of scale insects, making it an effective pesticide for controlling various scale insects. Generally, a 10-fold dilution is used in winter and a 20-fold dilution in summer. A 5-fold dilution of 40% dimethoate can also be applied to the stems. ③ Improve ventilation and light penetration in camellias to inhibit the growth and reproduction of scale insects.

　　Stem worms

　　[Risk Status] This insect primarily attacks the shoots of camellias. Affected shoots initially appear wilted and eventually die. Generally, it primarily affects spring shoots in March and April, and summer shoots in August and September. Affected shoots will show early signs of insect infestation and excrement, eventually drying out completely.

　　【Control Methods】① Prune and burn branches infested with stem borers. ② Use light traps to kill adult borers. ③ During the peak adult stage, spray with a 500-fold dilution of 20% dimethoate emulsion or a 1000-fold dilution of 90% trichlorfon; during the larval stage, spray with a 500-fold dilution of 90% trichlorfon.

　　Black thorn whitefly

　　[Risk Situation] The black spiny whitefly primarily threatens camellia leaves by absorbing their sap. Its exudate can lead to a large-scale outbreak of sooty mold, severely affecting the normal photosynthesis of camellias and causing significant flower drop.

　　[Control Methods] ① In winter or early spring, prune infested branches and leaves and destroy them to eliminate the source of infestation. ② During the peak hatching period of nymphs, spray with 25% phosmet or 50% malathion at 800-1000 times dilution; or spray with 40% dimethoate, 50% dimethoate, or 50% fenitrothion at 10 times dilution; or spray with pymetrozine at 1000 times dilution, once every 7 days for best results.