Occurrence and Control of Carnation (Dianthus caryophyllus) Leaf Spot
Occurrence and Control of Carnation Leaf Spot
Carnation, also known as clove pink or musk carnation, is a perennial herbaceous flower. It originated in Europe and America. Since its introduction, because of its large, beautiful, and richly colored flowers, it is often cultivated in greenhouses for cut flower production. It can also be cultivated in open fields in flower beds and is very popular. However, carnation is highly susceptible to leaf spot, which affects its growth and development and reduces the yield and quality of cut flowers. Based on years of observation and control trials, the author has summarized the occurrence pattern and control methods of carnation leaf spot as follows: Symptoms and Occurrence Pattern of Carnation Leaf Spot. The pathogen of carnation leaf spot overwinters as mycelium and conidia on diseased plant residues and can survive in soil for about one year. When temperatures rise and leaf surfaces remain wet for extended periods, the pathogen grows rapidly. The optimum temperature for mycelial growth is 25-30°C (26°C being optimal), and conidia begin to germinate at 18-27°C (24°C being optimal). The pathogen spreads through air currents and water, entering through stomata, wounds, or by direct penetration, with an incubation period of 10-60 days. Therefore, the disease can occur year-round in greenhouse cultivation and from April to November in open-field cultivation. The disease occurs on leaves and stems, and sometimes on flowers. When it occurs on leaves, the lesions initially appear as pale green water-soaked small round spots, gradually expanding into nearly circular, oval, or elongated large spots that turn purplish-brown, with the center of the lesion slowly dying and becoming grayish-white. The entire leaf becomes distorted and hangs wilted on the stem. When the disease infects stems, it mostly occurs at branch forks and at wounds caused by bud removal. The lesions are elongated and grayish-brown; in severe cases, the lesions girdle the stem, causing the upper branches and leaves to die. When the disease infects flowers, it often causes damage on pedicels and bracts; when there are many lesions on the bracts, the flowers fail to open or become deformed.Control Measures. 1. Select healthy, disease-free cuttings, remove diseased plant residues, keep plant surfaces as dry as possible, and implement crop rotation of 2 years or more in locations with good ventilation, light, and drainage. Greenhouses should maintain good ventilation, and ventilation before dusk is very important. 2. Since this disease can occur year-round, a preventive fungicide must be sprayed once a week, such as maneb, zineb, iprodione, or chlorothalonil, etc. Especially spray promptly after cutting flowers; 75% chlorothalonil, 50% captan at 500 times dilution, or 1% Bordeaux mixture can all be used.
Occurrence and Control of Carnation Leaf Spot
News from the China Landscape Web on June 8: Carnation, also known as clove pink or musk carnation, is a perennial herbaceous flower. It originated in Europe and America. Since its introduction, because of its large, beautiful, and richly colored flowers, it is often cultivated in greenhouses for cut flower production. It can also be cultivated in open fields in flower beds and is very popular. However, carnation is highly susceptible to leaf spot, which affects its growth and development and reduces the yield and quality of cut flowers. Based on years of observation and control trials, the author has summarized the occurrence pattern and control methods of carnation leaf spot as follows:
Symptoms and Occurrence Pattern of Carnation Leaf Spot
The pathogen of carnation leaf spot overwinters as mycelium and conidia on diseased plant residues and can survive in soil for about one year. When temperatures rise and leaf surfaces remain wet for extended periods, the pathogen grows rapidly. The optimum temperature for mycelial growth is 25-30°C (26°C being optimal), and conidia begin to germinate at 18-27°C (24°C being optimal). The pathogen spreads through air currents and water, entering through stomata, wounds, or by direct penetration, with an incubation period of 10-60 days. Therefore, the disease can occur year-round in greenhouse cultivation and from April to November in open-field cultivation. The disease occurs on leaves and stems, and sometimes on flowers. When it occurs on leaves, the lesions initially appear as pale green water-soaked small round spots, gradually expanding into nearly circular, oval, or elongated large spots that turn purplish-brown, with the center of the lesion slowly dying and becoming grayish-white. The entire leaf becomes distorted and hangs wilted on the stem. When the disease infects stems, it mostly occurs at branch forks and at wounds caused by bud removal. The lesions are elongated and grayish-brown; in severe cases, the lesions girdle the stem, causing the upper branches and leaves to die. When the disease infects flowers, it often causes damage on pedicels and bracts; when there are many lesions on the bracts, the flowers fail to open or become deformed.
Control Measures
1. Select healthy, disease-free cuttings, remove diseased plant residues, keep plant surfaces as dry as possible, and implement crop rotation of 2 years or more in locations with good ventilation, light, and drainage. Greenhouses should maintain good ventilation, and ventilation before dusk is very important.
2. Since this disease can occur year-round, a preventive fungicide must be sprayed once a week, such as maneb, zineb, iprodione, or chlorothalonil, etc. Especially spray promptly after cutting flowers; 75% chlorothalonil, 50% captan at 500 times dilution, or 1% Bordeaux mixture can all be used.