Symptoms and control methods of Botrytis cinerea in Phalaenopsis

Botrytis cinerea is one of the most common diseases in the production of Phalaenopsis, which often occurs in its growing season, especially in the greenhouse in winter and spring, the pathogen can infect any part of the plant. If the cultivation management is relaxed, it is more conducive to the occurrence and epidemic of the disease, and in serious cases, it can cause a large number of fallen flowers and leaves, which not only affects the flowering of the plant, but also directly reduces the ornamental value and yield of Phalaenopsis.

(1) conditions for onset of the disease

Warmth and humidity are the main conditions for the epidemic of Botrytis cinerea. That is, the disease is most likely to occur when the relative humidity is about 90% and the temperature is 18-25 ℃. When the air humidity is high, the disease develops rapidly; on the contrary, the disease develops slowly and there is little gray mold; the soft basin is placed too densely, or the drainage is not smooth, and the greenhouse with poor ventilation occurs seriously; if the nitrogen fertilizer is too much, the plant tissue is tender and weak, the disease is serious. After the continuous overcast and low temperature, when the weather clears up and the temperature rises, gray mold is easy to break out. When the disease occurs, the mature conidia are transmitted by air flow, irrigation water, Rain Water, dripping water in greenhouse and field operation. The pathogen has strong pathogenicity to floral organs and leaves. If the plant is strong, it is not easy to be infected.

(2) harmful symptoms

The disease mainly harms the leaves and flowers of Phalaenopsis. The damage to the leaves mainly occurred on the back of the leaves, showing a brown disease, which distributed unevenly, affecting the glossiness of the leaves; about 24 hours after the flower was damaged, there were scattered translucent round spots on the petals and calyx, showing a water soak. after that, the spots turned brown to dark brown, the edges were pink, and the number of spots increased gradually from flower damage to shedding. In the white series of flowers, the disease spot is more eye-catching, when the occurrence is serious, the flower withered early and the bud withered. Because its flowering period is as long as 2-3 months, the chance of infection increases, especially the flowers blooming earlier, are more likely to be infected with the disease.

(3) Prevention and control methods

1. Reduce the source of infection and remove diseased flowers, diseased leaves, withered flowers and weeds inside and outside the garden at any time.

2. Strengthen the field management (1) pay attention to control the amount of nitrogen fertilizer to prevent excessive growth and aggravate the disease, so as to keep the orchid plant strong and improve disease resistance. (2) in the early stage of the disease, the part of the disease was removed in time and burned centrally. (3) pay attention to the space between the soft basins so that they can be ventilated and transparent. (4) watering should be "dry and wet" to prevent stagnant water. (5) in the process of management, plant damage should be reduced as much as possible to prevent bacteria from invading from the wound. (6) timely and appropriate ventilation to avoid cold injury and heat injury.

3. Drug prevention and treatment (1) it can be prevented by spraying 2500 times of 70% methyl Dobaojing wettable powder or 2000 times of 50% acetaminophen wettable powder. (2) at the initial stage of the disease, 2000 times of 50% Sukeling wettable powder or 65% 1500 times of anti-aldicarb wettable powder were sprayed for prevention and treatment. (3) at the initial stage of flowering, 2000 times of chlorphenamine wettable powder or 1500 times of Iputong wettable powder were sprayed, and prevention was sprayed every 2 to 4 weeks. At the time of onset, 1000 times of Lelidan or 2000 times of Sukeling were sprayed every 7 days for prevention and treatment. (4) in order to avoid drug resistance of Botrytis cinerea, effective pesticides should be applied alternately.