Control of Orchid Brown Rot

Control of Orchid Brown Rot

Orchids are susceptible to brown rot due to hot summer temperatures, excessive water application, soil moisture, hardening, poor air permeability, and mechanical damage to pseudobulbs. Its pathogens are very miscellaneous, mainly Phytophthora palmifera and a small amount of Phytophthora nicotiana. Most of the disease occurred on the leaf base and pseudobulb of one or two years old plants, and then the affected parts gradually became soft, light brown until dark brown; at the same time, the conducting tissue of pseudobulb became black, the central leaf wilted, yellow from top to bottom. Orchids are mostly concentrated into clusters, pseudobulbs are connected, and the bacteria spread to normal plants around the diseased plants quickly through the tutoring tissues of pseudobulbs and external contact. The disease develops rapidly and will affect the whole basin in a few days. High temperature and heavy rain from June to August were the most frequent periods of brown rot. Observe orchids every morning and evening to strengthen prevention. In addition to the prevention of orchid pot to use fried, sun and other methods, sterilization of the culture soil, usually every 10 days with the same amount of Bordeaux mixture or 50% Tuijunte 800 times spray once. Once the orchid leaves in the pot are found to have disease spots, they should be isolated from healthy orchids immediately, the pot soil should be changed, and the diseased plants should be completely removed and burned with a sterilized single-sided blade. Keep the normal plants, rinse the roots with clean water, and cut off the rotten roots. If only 1~2 seedlings can be retained and the root system is too poor, the orchid leaves are dehydrated and atrophied, half or more leaves can be cut off, and then the plants are completely immersed in 0.3% potassium permanganate solution, and then taken out; the wound part is smeared with Tujunte or carbendazim powder, the root is upward, the leaves are as follows, and the shade is dried for more than 10 minutes; the culture soil (or 65% zinc 600 times solution mixed with bamboo root mud) is used to kill bacteria, and re-planting is carried out. The culture soil of diseased orchids can no longer be used.

After planting orchids should be placed in a cool place for maintenance, pay attention to ventilation and light transmission. No fertilizer was applied that year, and the pot soil remained slightly dry. Water cannot penetrate the heart of the leaf. Morning and evening with water spray, leaves appear even small dots but do not flow appropriate. Potassium dihydrogen phosphate and urea 0.05% each can be added to the sprayed water to supplement the nutrient consumption of the potted orchids and promote new roots and buds. Growth can resume after a month. After careful management, leaf buds will also be issued that year.