Identification of Symptoms of Gray Mold in Phalaenopsis and Its Prevention and Control Methods
Orchid gray mold is also called orchid flower rot. This disease may break out in flower nurseries in both northern and southern China, mainly harming orchid family plants, among which it causes relatively severe damage to horticultural treasures such as Phalaenopsis, Cymbidium hybridum and Cymbidium sinense, seriously affecting the ornamental value of these flowers. The following is an introduction by Qinnong Network on the symptoms and prevention of gray mold in Phalaenopsis.
Gray mold in Phalaenopsis mainly harms floral organs, sepals, petals and pedicels, and sometimes also harms leaves and stems. In severe cases, it causes spots on flowers and gray mold everywhere. Since Phalaenopsis is an ornamental orchid, this is undoubtedly a devastating disaster.
I. Disease Identification
When Phalaenopsis is infected with gray mold, the harmed leaves develop brown diseased masses unevenly distributed on the back of the leaves, which affects leaf photosynthesis and causes poor orchid growth. When petals and sepals are infected by the pathogen, initially water-soaked, translucent small spots appear on the petals and sepals, after which the lesions turn brown and gradually expand into round patches, and the lesions merge with each other. After the disease develops, the entire flower turns dark brown with pink edges, rotting and withering. When pedicels are harmed by the pathogen, small water-soaked spots appear in the early stage, then gradually develop into dark brown elliptical lesions, and after about a week the flower dies. Orchids harmed early on will have flowers that wither prematurely and buds that dry up, and orchids that open early are most susceptible to gray mold.
II. Disease Occurrence Pattern
Diseased residues left in flower pots harbor large amounts of pathogens. When suitable temperature and humidity conditions are encountered, the pathogen spores germinate again and become a secondary infection source. When the disease occurs, the large number of conidia produced is again spread by airflow, rainwater, irrigation or human handling and touching. When orchids are grown in greenhouses in winter and spring, the temperature and humidity both meet the conditions for the occurrence of this disease. When the temperature is around 18 to 25 degrees and the relative humidity is around 90 percent, gray mold is easily triggered.
III. Prevention and Control Methods
1. Selection of growing medium
Phalaenopsis has epiphytic roots, which are fleshy aerial roots. Therefore, the selected medium must be breathable and have fertilizer-retaining properties. Commonly used media are sphagnum moss, coconut coir, pine bark and so on. For base fertilizer, use decomposed farmyard manure, which can be slowly absorbed by the roots. Liquid fertilizer is often used, diluted 1500 to 2000 times. Orchids cultivated in such a medium are robust and rarely develop the disease.
2. Pay attention to orchid room cleanliness
The place where orchids are grown should be kept hygienic, and surrounding dead branches and rotten leaves should be removed as much as possible. When winter arrives, the orchids should be moved indoors. Before moving them back, clean the room first, then remove diseased flowers and leaves and disinfect with limewater, so as to reduce the pathogen base as much as possible.
3. Strengthen management
When growing orchids, management must be strengthened and care taken carefully, with special attention to indoor temperature changes and timely adjustment, and close attention to the growth of the orchids. Conduct regular inspections. When diseased flowers and leaves are found, measures should be taken promptly: wrap the diseased orchids sealed in plastic bags, take them together with the pots outdoors for disposal, and do not put them back in the greenhouse, so as to reduce pathogen infection, and carry out appropriate wind protection according to weather conditions.
4. Early stage of disease
Spray the entire pot with carbendazim for disinfection and sterilization. When placing orchids, do not keep them sealed; there should be a certain distance between pots to prevent transmission, ensure ventilation and light, and prevent water accumulation, which would increase indoor humidity. In daily orchid management, be careful and minimize wounds on the orchids to prevent pathogens from invading through wounds.
5. Chemical control
Agents such as carbendazim and chlorothalonil can all treat gray mold and can be bought in ordinary flower shops. When applying the chemicals, take care to use them in rotation to prevent resistance.
The above is Qinnong Network's summary of the symptoms and prevention measures of gray mold in Phalaenopsis. It can be seen that because this type of disease is relatively common, the prevention and treatment methods are relatively mature. Paying attention to observation during daily care and applying medication promptly after the disease occurs can minimize losses.