What are the common pest and disease control methods for Dendrobium orchids?

　　1. Diseases:

(1) Soft rot: also known as bacterial brown spot, it mostly infects from the rhizome, but can also occur on leaves. It starts as small water-soaked dark green spots, which gradually expand into brown, softened, rotting lesions. A secretion oozes from the rotting area and is accompanied by a foul odor. The pathogen can spread through watering. High temperature and high humidity favor the development of the disease. Once an infected plant is found, it should be isolated and destroyed promptly, and treated with drugs such as agricultural streptomycin, Bordeaux mixture, or methyl thiophanate-phosphorus.

(2) Black spot: this is the main disease harming Dendrobium orchids, occurring on the leaves. It begins as small brown spots, which later expand into nearly circular lesions with necrotic centers; the lesions are grayish brown and 0.5-1.0 cm in diameter. In severe cases, the lesions join together into patches, causing the leaves to turn yellow and drop off.

　　2. Pests:

(1) Aphids: they mainly harm the young leaves and flower buds of Dendrobium orchids, piercing the epidermis with their piercing-sucking mouthparts to suck out the plant's sap and nutrients, causing the leaves and new shoots to become deformed and withered, and they can also facilitate the invasion of diseases. Control methods: improve ventilation and improve the cultivation environment, combined with pesticide spraying; spray with 20% fenvalerate at 1500 times dilution or 40% omethoate at 1000 times dilution for control.

(2) Scale insects: common pests in Dendrobium cultivation, mainly parasitic on the undersides of leaves or inside leaf sheaths. They occur in environments with low air humidity and poor ventilation. In the early stage of infestation, the leaves turn yellow, affecting photosynthesis; in severe cases, the plant dies or cannot grow and bloom normally. In addition to improving ventilation, when only a small number occur, they can be brushed off with a soft brush. For chemical control, spray with 50% malathion or 25% Jiesijing at 800-1000 times dilution once a week, for 3-4 consecutive sprays.

(3) Snails and slugs: they are more commonly seen during long periods of dampness or the plum rain season. They crawl out at night to bite and eat the new shoots or root tips of Dendrobium orchids, severely hindering growth. You can remove weeds and moss from the ground; when only a small number occur, handpick them at night or scatter quicklime on the ground and in wall corners to repel and kill them; when they occur over a large area, treat with 80% Miewoling or 90% trichlorfon.