A brief discussion on the Prevention and Control of two Diseases of Orchid

According to the records of orchid growth and disease occurrence, control measures and effects in Xiamen Botanical Garden in the past two years, the orchid brown rot and anthrax diseases and control measures were discussed.

Due to high temperature in hot summer, excessive water application, over-wet soil, poor air permeability, mechanical damage to pseudobulbs and so on, orchids are easy to be infected with brown rot. The pathogens were very miscellaneous, mainly Phytophthora palms and a small amount of tobacco Phytophthora. Water-stained patches appeared on the leaf base and pseudobulbs of the 2012 plants, and then the damaged parts gradually softened, showing light brown to dark brown; at the same time, the conducting tissue of the pseudobulb turned black, the central leaf wilted and yellowed from top to bottom. The orchid is concentrated in clusters, and the pseudobulbs are connected. The pathogen is infected by the conducting tissue and external contact of the pseudobulbs, and quickly spreads to the normal plants around the diseased plants. The course of the disease develops rapidly, and the whole basin will be affected in a few days. The high temperature and heavy rain from June to August is the frequent occurrence period of brown rot. Pay attention to the orchid every morning and evening and strengthen the prevention. Prevention measures, in addition to the orchid turning pot to use stir-frying, sun and other methods, sterilization of the culture soil, usually every ten days with the same amount or with Bordeaux solution or with 50% bacillus 800 times solution spray. Once diseased spots are found in the leaves of orchids in the basin, they should be isolated from healthy orchids immediately, change the soil, thoroughly sweep and burn the diseased plants with sterilized one-sided blades, retain the normal plants, rinse the roots with clean water, and cut off the rotten roots. If only 1 Mei 2 seedlings can be retained and the root system is too poor, when the orchid leaves lose water and shrink, cut off half or more of the leaves, then completely soak the plant in 0.3% potassium permanganate and then take it out, and the wound part is smeared with carbendazim or carbendazim powder, the root is facing up, the leaf is facing down, and the shade is hung for more than 10 minutes, then mix well with sterilized culture soil or 65% zinc 600 times bamboo root mud, then replant. The culture soil of diseased orchids can no longer be used.

After overplanting, orchids should be protected in a cool place, pay attention to ventilation and light, no fertilization in that year, basin soil protection is slightly dry, good drainage, watering can not irrigate the heart of human leaves. After spraying with clear water in the morning and evening, uniform and small dots appear but not dirty. The spraying water can add 0.5% potassium dihydrogen phosphate and 0.5% urea to supplement the nutritional consumption of turned-pot orchids and promote new roots and buds, which can grow stably after one month. After careful management, leaf buds will be sent out that year, and they will grow at least close to the height of the plant in the coming year.

The occurrence of orchid anthracnose is common and serious, with reddish-brown semicircular spots at the initial stage, dark brown spots at the later stage, sometimes yellow halos at the edges, and small black spots arranged in rings in the center from grayish brown to grayish white. When the leaf disease spot changes downward, the leaf forms a dead section. When the disease at the base of the leaf is serious, it will cause the whole plant to die. The pathogen was cuddled with orchids, and the bacteria overwintered on the diseased leaves of remnant plants with mycelium. The disease class on the old leaves began to occur in early April and developed rapidly in May and June. After July, the new leaves germinated and the disease spots also occurred. Methods of prevention and control: the orchid room should be ventilated and transparent, the flowerpot should not be placed too dense, it should be placed in the place of wind and rain, and the watering should be watered from the edge of the basin. Pay attention to avoid frost, cause damage, and reduce the chance of invading the beam. In spring and autumn, spray 50% carbendazim wettable powder or 50% benzoate wettable powder 1000 times or 50% topazine wettable powder 1000 times, every 10 days, a total of 3 Lok 4 times, with a certain effect. (Zhang Hong)