Symptoms and Control Methods of Gray Mold in Carnations

[Introduction]

This disease is a common disease of carnations grown in greenhouses and plastic tunnels. It can cause brown spots on petals or cause petals to rot, seriously affecting the quality of cut flowers.

[Symptoms]

Gray mold in carnations mainly begins at the edges of petals, where light brown water-soaked spots appear, after which several petals become entangled together by the growth of gray fungus. If the environment is humid, the petals rot and bear gray mold. When flower buds are affected, there are irregular water-soaked spots, which become soft and rot, and gray mold also develops.

[Pathogen]

It is Botrytis cinerea Pers.

[Transmission Route]

The pathogen overwinters in the form of sclerotia in diseased plant residues or in the soil. When the temperature is around 20°C and the humidity is very high, this disease occurs severely. When grown in plastic tunnels and greenhouses, because the temperature is low and the humidity is high in early spring and autumn, this disease often breaks out severely. Tissue-cultured seedlings are more disease-resistant than cuttings. Red-flowered varieties are more disease-resistant than yellow-flowered varieties.

[Control Methods]

1. Increasing temperature and ventilation to keep the humidity in the greenhouse low gives good disease control results. Diseased plants and flowers should be removed immediately.

2. Chemical control: In the early stage of the disease, the following application methods can be used:

1) Smoke method (suitable for greenhouses and plastic tunnels): Trial use 10% procymidone smoke agent at 200-250 grams per mu each time, or 45% chlorothalonil smoke agent at 250 grams per mu, fumigating for 3-4 hours.

2) Dust method (suitable for greenhouses and plastic tunnels): In the evening, dust 10% procymidone dust, or 5% chlorothalonil dust, or 10% shameiling dust, at 1 kilogram per mu each time, once every 9-11 days, used continuously or alternately with other control methods for 2-3 times.

3) Spray method: Use 50% procymidone wettable powder at 2000 times dilution, or 50% iprodione wettable powder at 1000-1500 times dilution, or 50% thiophanate-methyl wettable powder at 500 times dilution, or 50% sulfur suspension concentrate at 200-300 times dilution, or 2.5% difenoconazole emulsifiable concentrate at 4000 times dilution (once every 20 days), once every 6-8 days, spraying 3 times.