Botrytis cinerea of Phalaenopsis and its control measures

Orchid gray mold, also known as orchid rot. Flower beds occur from time to time in the south and north of China, which endanger not only the orchids of Orchidaceae, but also Phalaenopsis, Cartland, Dendrobium, Magnolia, Crane and other flower plants. Among them, horticultural treasures such as Phalaenopsis, Cymbidium and Cymbidium suffer more seriously.

1. Symptoms

Botrytis cinerea of Phalaenopsis mainly harms flower organs, sepals, petals, pedicels, and sometimes leaves and stems. In the early stage of the disease, after the petals and calyx are infected, small translucent water stains can be produced in 24 hours, and then the spots turn brown, and sometimes there are white or light pink circles around the spots. The number of disease spots on each flower varies, but when the flowers begin to wither, the disease spots increase rapidly, and the petals become dark brown and rot. When the humidity is high, fluffy, mouse gray growth grows from the rotting flowers, that is, the conidiophores and conidia of pathogens. Pedicel and flower stem infection, early appearance of water-stained spots, gradually expanded into round to long oval spots, dark brown, slightly sunken. When the spot expands to a week around the stem, the flower dies. When the leaves are damaged, the leaf tips are scorched. There are 2 to 3 peaks of the disease in early spring, autumn and winter every year. In severe cases, the flowers are full of disease spots and gray mold can be found everywhere, which is a devastating disaster for orchids that enjoy leaves like flowers or specialize in flowers. When the temperature is high, the disease is limited to the older and withering flowers. Many kinds of orchids can be infected with this disease when the flowers begin to grow old or become weak. Phalaenopsis Botrytis cinerea and its control of orchid gray mold, also known as orchid flower rot. Flower beds occur from time to time in the south and north of China, which endanger not only the orchids of Orchidaceae, but also Phalaenopsis, Cartland, Dendrobium, Magnolia, Crane and other flower plants. Among them, horticultural treasures such as Phalaenopsis, Cymbidium and Cymbidium suffer more seriously. 1. Symptoms Phalaenopsis Botrytis cinerea mainly harms flower organs, sepals, petals, pedicels, and sometimes leaves and stems. In the early stage of the disease, after the petals and calyx are infected, small translucent water stains can be produced in 24 hours, and then the spots turn brown, and sometimes there are white or light pink circles around the spots. The number of disease spots on each flower varies, but when the flowers begin to wither, the disease spots increase rapidly, and the petals become dark brown and rot. When the humidity is high, fluffy, mouse gray growth grows from the rotting flowers, that is, the conidiophores and conidia of pathogens. Pedicel and flower stem infection, early appearance of water-stained spots, gradually expanded into round to long oval spots, dark brown, slightly sunken. When the spot expands to a week around the stem, the flower dies. When the leaves are damaged, the leaf tips are scorched. There are 2 to 3 peaks of the disease in early spring, autumn and winter every year. In severe cases, the flowers are full of disease spots and gray mold can be found everywhere, which is a devastating disaster for orchids that enjoy leaves like flowers or specialize in flowers. When the temperature is high, the disease is limited to the older and withering flowers. Many kinds of orchids can be infected with this disease when the flowers begin to grow old or become weak. 2. The pathogen of the disease was identified as Sclero-tiniafuckeliana (deBary) Fuck, which belongs to ascomycetes. The asexual state is BotrytiscinereaPers.exFf. It is called Botrytis cinerea and belongs to Trichoderma. When the condition is bad, sometimes the sclerotia grows in flaky sclerotia, and the sclerotia substrates grow on the surface of the sclerotia with different sizes, most of which are 3~4.5mm × l.8~3mm, and the smaller ones are only 11mm in diameter. On Cha's medium, most of the sclerotia were semi-buried, 2.5~15mm in size, round to oblong. The sexual spore stage is common, the silk seminal apparatus is white, the population is grayish white, the sexual spore is spherical, the size is 3 ~ 4 microns. The colony produced by asexuality was grayish white at first and brown later. Conidiophores scattered or clustered in colonies, light brown to brown, with septum, 280mm 350 μ m × 12 μ m 24 μ m, apical 1 × 2 branched, slightly inflated, some rod-shaped, dense peduncles and a large number of conidia. Conidia are widely ovoid, many, unicellular, nearly colorless, 6 μ m 8 μ m × 5 μ m 12 μ m in size. Under scanning electron microscope, the surface of spores was smooth. Among ornamental plants, in addition to infecting orchids, it can also infect many kinds of flowers, such as Begonia, cyclamen, calendula, platypus, pedicel begonia, big rock tree, canna, drunken butterfly, orchid, coral flower, dahlia, arrow lotus, day lily, mulberry, gladiolus, petunia, Zhu Dinghong, chrysanthemum, marigold, poinsettia, camellia, spring primrose, rose, cherry, rhododendron, string red, calla lotus and other flowers. 3. Transmission route and pathogenic condition bacteria overwintered in 5~12cm soil by sclerotia. In the following spring, when the temperature was 7-8 ℃ and the relative humidity was above 88%, a large number of hyphae and conidia were produced on the sclerotia, which were spread by air flow, water droplets or dew and horticultural operations. The spread of the disease is gradual, and after the seedlings are invaded, the pathogen can be colonized. It often expands with the growth of the plant, harms the stem or leaf or lurks before budding and flowering. After flowering, as long as the disease conditions are suitable, the flower organ will soon become infected. The occurrence of Botrytis cinerea is greatly affected by the conditions of the disease. Sclerotia could germinate under the condition of 5-30 ℃. It only took 1 day to germinate at 21 ℃ and 5 days at 5 ℃. The threshold temperature of mycelial development was 2 ℃, the highest was 31 ℃, and the optimum was 20 ℃. The optimum temperature for spore germination was 18 ℃, and 21 ℃ germinated after 24 hours. The germination rate was 72.6% after 35 ℃ culture, only a few spores germinated, but 37 ℃ could not germinate. The humidity requirements of the bacteria are often stricter than the temperature, RH below 84% spores can not germinate, higher than 88% to germinate normally, 92% to 95% spore germination rate is the highest. It took 15 days for RH80% to produce conidia and only 3 days for RHl00% to produce a large number of conidia. In addition, high humidity is beneficial to the invasion, expansion and epidemic of bacteria, and the incubation period can also be shortened. The infection of this bacteria needs certain nutrition, such as the petals that are about to wither or the stigma that has been powdered, and the stems and leaves with wounds are easy to be infected by Botrytis cinerea. After the pathogen invades, it first saprophytes, and when it forms a population, it infects the vigorous healthy flower or stem. The epidemic of the disease in orchid nursery or shed often requires the process of bacteria accumulation. Botrytis cinerea of Phalaenopsis is mainly infected by calyx, petals and stigmas, and its pathogen is about to wither flowers. Therefore, the weather conditions of orchid flowering have a great influence on the disease. During this period, the temperature is 718 ℃ and the RH is higher than 88%. It is easy to get sick. The relative humidity in plastic sheds, solar greenhouses and rooms can often meet the requirements of the disease, and indoor air temperature is the limiting factor for the epidemic of the disease. Botrytis cinerea begins to occur when the temperature is less than 18 ℃. When the temperature reaches more than 20 ℃ and the humidity drops to about 60%, Botrytis cinerea gradually stops. It was observed that the disease was serious when it rained continuously in winter and spring in Guangdong, and it was easy to be prevalent in Zhejiang, Shanghai and Fujian during the rainy season. In the middle of November 1999, the heavy fog lasted for several days in Beijing, and the humidity met the needs of the disease. at this time, the room temperature of the unheated greenhouse orchid nursery was only 15: 17 ℃, which was disadvantageous to the growth of orchids, but beneficial to the epidemic of Botrytis cinerea, so there was another peak. 4. Prevention and control methods (1) strengthen management, carefully maintain and control the temperature and humidity of the environment, especially in early spring and early winter, so that the temperature or humidity of orchids is disadvantageous to the occurrence of Botrytis cinerea. Greenhouse or bedroom should pay attention to heating and ventilation to prevent moisture retention; do not splash on the flowers when watering, if watering from the top must be carried out after the sun comes out in the morning, so that the water on the leaves dries faster. Botrytis cinerea is an air-borne disease, the disease residue should be removed in time to prevent the spread of spores. (2) spraying 50% procymiodone wettable powder 1500 times solution or 50% iprodione, 50% vinclozolin wettable powder 1000 times solution, 50% carbendazim (benomyl) wettable powder 1000 times solution at the initial stage of drug control, about 10 days, 2 times in a row. In the old bud stage, the efficacy of 75% chlorothalonil wettable powder and 50% carbendazim wettable powder 1000 times is stable. If the disease is serious, it must be taken before flowering and sprayed again 7 days later, but for colored flowers, carbendazim sometimes leaves a faint visible stain. According to Lu Liyan in Taiwan, orchid seedlings just out of the bottle can control flower rot by spraying 58% metalaxyl manganese zinc wettable powder and 50% metalaxyl granule 25g/ cubic meters on the surface of the cultivation medium immediately after transplanting. Areas with resistance to the above fungicides can use 65% thiocarbamate wettable powder 1200 times or more than 50% carbendazim (carbendazim) wettable powder 900x solution, about once every 10 days, and connect 2 times for 3 times. In order to prevent the development of drug resistance and improve the control effect, alternate or compound use of drugs is advocated. Botrytis cinerea of Phalaenopsis and its control methods

Orchid gray mold, also known as orchid rot. Flower beds occur from time to time in the south and north of China, which endanger not only the orchids of Orchidaceae, but also Phalaenopsis, Cartland, Dendrobium, Magnolia, Crane and other flower plants. Among them, horticultural treasures such as Phalaenopsis, Cymbidium and Cymbidium suffer more seriously.

1. Symptoms

Phalaenopsis gray mold mainly harms floral organs, sepals, petals, pedicels, and sometimes leaves and stems. In the early stage of the disease, after the petals and calyx are infected, small translucent water stains can be produced in 24 hours, and then the spots turn brown, and sometimes there are white or light pink circles around the spots. The number of disease spots on each flower varies, but when the flowers begin to wither, the disease spots increase rapidly, and the petals become dark brown and rot. When the humidity is high, fluffy, mouse gray growth grows from the rotting flowers, that is, the conidiophores and conidia of pathogens. Pedicel and flower stem infection, early appearance of water-stained spots, gradually expanded into round to long oval spots, dark brown, slightly sunken. When the spot expands to a week around the stem, the flower dies. When the leaves are damaged, the leaf tips are scorched. There are 2 to 3 peaks of the disease in early spring, autumn and winter every year. In severe cases, the flowers are full of disease spots and gray mold can be found everywhere, which is a devastating disaster for orchids that enjoy leaves like flowers or specialize in flowers. When the temperature is high, the disease is limited to the older and withering flowers. Many kinds of orchids can be infected with this disease when the flowers begin to grow old or become weak.

2. Pathogen

The pathogen of the disease was identified as Sclero-tiniafuckeliana (deBary) Fuck, which belongs to ascomycetes. The asexual state is BotrytiscinereaPers.exFf. It is called Botrytis cinerea and belongs to Trichoderma. When the condition is bad, sometimes the sclerotia grows in flaky sclerotia, and the sclerotia substrates grow on the surface of the sclerotia with different sizes, most of which are 3~4.5mm × l.8~3mm, and the smaller ones are only 11mm in diameter. On Cha's medium, most of the sclerotia were semi-buried, 2.5~15mm in size, round to oblong. The sexual spore stage is common, the silk seminal apparatus is white, the population is grayish white, the sexual spore is spherical, the size is 3 ~ 4 microns. The colony produced by asexuality was grayish white at first and brown later. Conidiophores scattered or clustered in colonies, light brown to brown, with septum, 280mm 350 μ m × 12 μ m 24 μ m, apical 1 × 2 branched, slightly inflated, some rod-shaped, dense peduncles and a large number of conidia. Conidia are widely ovoid, many, unicellular, nearly colorless, 6 μ m 8 μ m × 5 μ m 12 μ m in size. Under scanning electron microscope, the surface of spores was smooth. Among ornamental plants, in addition to infecting orchids, it can also infect many kinds of flowers, such as Begonia, cyclamen, calendula, platypus, pedicel begonia, big rock tree, canna, drunken butterfly, orchid, coral flower, dahlia, arrow lotus, day lily, mulberry, gladiolus, petunia, Zhu Dinghong, chrysanthemum, marigold, poinsettia, camellia, spring primrose, rose, cherry, rhododendron, string red, calla lotus and other flowers.

3. the route of transmission and the condition of the disease.

The pathogen overwintered in 5~12cm soil with sclerotia. In the following spring, when the temperature was 7-8 ℃ and the relative humidity was above 88%, a large number of hyphae and conidia were produced on the sclerotia, which were spread by air flow, water droplets or dew and horticultural operations. The spread of the disease is gradual, and after the seedlings are invaded, the pathogen can be colonized. It often expands with the growth of the plant, harms the stem or leaf or lurks before budding and flowering. After flowering, as long as the disease conditions are suitable, the flower organ will soon become infected. The occurrence of Botrytis cinerea is greatly affected by the conditions of the disease. Sclerotia could germinate under the condition of 5-30 ℃. It only took 1 day to germinate at 21 ℃ and 5 days at 5 ℃. The threshold temperature of mycelial development was 2 ℃, the highest was 31 ℃, and the optimum was 20 ℃. The optimum temperature for spore germination was 18 ℃, and 21 ℃ germinated after 24 hours. The germination rate was 72.6% after 35 ℃ culture, only a few spores germinated, but 37 ℃ could not germinate. The humidity requirements of the bacteria are often stricter than the temperature, RH below 84% spores can not germinate, higher than 88% to germinate normally, 92% to 95% spore germination rate is the highest. It took 15 days for RH80% to produce conidia and only 3 days for RHl00% to produce a large number of conidia. In addition, high humidity is beneficial to the invasion, expansion and epidemic of bacteria, and the incubation period can also be shortened. The infection of this bacteria needs certain nutrition, such as the petals that are about to wither or the stigma that has been powdered, and the stems and leaves with wounds are easy to be infected by Botrytis cinerea. After the pathogen invades, it first saprophytes, and when it forms a population, it infects the vigorous healthy flower or stem.

The epidemic of the disease in orchid nursery or shed often requires the process of bacteria accumulation. Botrytis cinerea of Phalaenopsis is mainly infected by calyx, petals and stigmas, and its pathogen is about to wither flowers. Therefore, the weather conditions of orchid flowering have a great influence on the disease. During this period, the temperature is 718 ℃ and the RH is higher than 88%. It is easy to get sick. The relative humidity in plastic sheds, solar greenhouses and rooms can often meet the requirements of the disease, and indoor air temperature is the limiting factor for the epidemic of the disease. Botrytis cinerea begins to occur when the temperature is less than 18 ℃. When the temperature reaches more than 20 ℃ and the humidity drops to about 60%, Botrytis cinerea gradually stops. It was observed that the disease was serious when it rained continuously in winter and spring in Guangdong, and it was easy to be prevalent in Zhejiang, Shanghai and Fujian during the rainy season. In the middle of November 1999, the heavy fog lasted for several days in Beijing, and the humidity met the needs of the disease. at this time, the room temperature of the unheated greenhouse orchid nursery was only 15: 17 ℃, which was disadvantageous to the growth of orchids, but beneficial to the epidemic of Botrytis cinerea, so there was another peak.

4. Prevention and control methods

The main results are as follows: (1) strengthen the management and carefully control the temperature and humidity of the environment, especially in the low temperature and high humidity seasons in early spring and early winter, so that the temperature or humidity of orchids is disadvantageous to the occurrence of Botrytis cinerea. Greenhouse or bedroom should pay attention to heating and ventilation to prevent moisture retention; do not splash on the flowers when watering, if watering from the top must be carried out after the sun comes out in the morning, so that the water on the leaves dries faster. Botrytis cinerea is an air-borne disease, the disease residue should be removed in time to prevent the spread of spores.

(2) spraying 50% procymiodone wettable powder 1500 times solution or 50% iprodione, 50% vinclozolin wettable powder 1000 times solution, 50% carbendazim (benomyl) wettable powder 1000 times solution at the initial stage of drug control, about 10 days, 2 times in a row. In the old bud stage, the efficacy of 75% chlorothalonil wettable powder and 50% carbendazim wettable powder 1000 times is stable. If the disease is serious, it must be taken before flowering and sprayed again 7 days later, but for colored flowers, carbendazim sometimes leaves a faint visible stain. According to Lu Liyan in Taiwan, orchid seedlings just out of the bottle can control flower rot by spraying 58% metalaxyl manganese zinc wettable powder and 50% metalaxyl granule 25g/ cubic meters on the surface of the cultivation medium immediately after transplanting. Areas with resistance to the above fungicides can use 65% thiocarbamate wettable powder 1200 times or more than 50% carbendazim (carbendazim) wettable powder 900x solution, about once every 10 days, and connect 2 times for 3 times. In order to prevent the development of drug resistance and improve the control effect, alternate or compound use of drugs is advocated.