How to Control Bacterial Wilt in Canna
Canna
In order to beautify the living environment and improve people's aesthetic appreciation, cannas have been planted in large strips along roadsides in recent years. With rich flower colors and a strong fragrance, they are deeply loved by people, but in some areas they are prone to devastating bacterial wilt, which seriously affects their landscape value. So what causes bacterial wilt in cannas? And what should be done when this problem occurs?
I. Symptoms
The pathogen infects the stems and root systems of the plants. During an epidemic period, it generally takes 10~15 days from infection to death of the plant. Most infections start from the roots, though some enter through the stems. The aboveground leaves of diseased plants lose water and turn yellow, wilt and droop, and gradually black streaks appear at the stem base or on the stem. After encircling the stem, the entire plant dies (Figure 1). When a necrotic root or stem is cut crosswise, after a few minutes a milky white or yellowish-brown bacterial ooze exudes from the cut surface. This is the pathogenic bacterium, and it is an important basis for diagnosing bacterial wilt outdoors. If the stem is cut lengthwise, strip-like dark brown streaks can also be seen.
II. Pathogen
Canna bacterial wilt (Pseudomonas solanacearum) is caused by infection by Pseudomonas solanacearum, a species in the order Pseudomonadales and the genus Pseudomonas. The bacterial cells are short rod-shaped, with bluntly rounded ends, and have 1~4 flagella at the poles (Figure 2). They stain Gram-negative. The size is 1.5~2.3 x 0.5~0.7 micrometers. The optimum temperature for pathogen growth and development is 34°C, with a maximum of 37°C and a minimum of 18°C. Its adaptable pH range is pH 6~8, with an optimum pH of 6.6.
III. Occurrence Pattern
The pathogen can survive in soil, plant residues and garbage mixtures. In any soil where infected plants such as peanut, tomato, eggplant, tobacco, beefwood, eucalyptus, chrysanthemum and dahlia have been grown, as well as in soil fertilizers and water sources that have come into contact with diseased residues of the flowers, stems, roots and leaves of these diseased plants, the bacterial wilt pathogen may exist and multiply. If such soil, water or fertilizer is used to cultivate cannas, bacterial wilt will occur. The pathogen can survive in soil for more than 1 year, and only 30 days and 90 days under dry or waterlogged conditions. The pathogen mainly invades through wounds on the host. Damage from wind and rain, insect feeding and human activities all create opportunities for the pathogen to invade. Surface runoff and root-to-root contact between plants are the main routes of spread within a small area. Long-distance spread relies on diseased tuber propagation material. Generally, the disease begins in March each year, is severe from June to October, and peaks from July to September. After typhoon rain, when the atmospheric temperature is 33~35°C and the relative humidity is above 80%, if the green space is waterlogged, bacterial wilt is most likely to become epidemic.
IV. Control Methods
1. Do not take tubers from diseased areas as propagation material. Enforce strict quarantine. If batches of diseased seedlings are found, they should be eliminated in batches.
2. Do not plant cannas in soil where bacterial wilt has occurred. If farmyard manure is to be applied, it should first be piled and composted and fully decomposed, or each square meter should be drenched with 6 kg of a 50-fold dilution of 40% formalin, then covered with plastic film for disinfection.
3. Do not cultivate or weed during the epidemic period, to avoid injuring the plants. If diseased plants are found, pull them out immediately, dig out the diseased soil, and sprinkle or drench around them with a 400~600-fold dilution of 25% Qingkuling, or a 3000~4000-fold dilution of 90% soil streptomycin, or sulfur powder. In diseased areas, it is best to drench or sprinkle the above agents once after a typhoon.
Canna Bacterial Wilt
Symptoms The pathogen infects the stems and root systems of the plants. During an epidemic period, it generally takes 10~15 days from infection to death of the plant. Most infections start from the roots, though some enter through the stems. The aboveground leaves of diseased plants lose water and turn yellow, wilt and droop, and gradually black streaks appear at the stem base or on the stem. After encircling the stem, the entire plant dies (Figure 1). When a necrotic root or stem is cut crosswise, after a few minutes a milky white or yellowish-brown bacterial ooze exudes from the cut surface. This is the pathogenic bacterium, and it is an important basis for diagnosing bacterial wilt outdoors. If the stem is cut lengthwise, strip-like dark brown streaks can also be seen.
Pathogen Canna bacterial wilt (Pseudomonas solanacearum) is caused by infection by Pseudomonas solanacearum, a species in the order Pseudomonadales and the genus Pseudomonas. The bacterial cells are short rod-shaped, with bluntly rounded ends, and have 1~4 flagella at the poles (Figure 2). They stain Gram-negative. The size is 1.5~2.3×0.5~0.7 micrometers. The optimum temperature for pathogen growth and development is 34°C, with a maximum of 37°C and a minimum of 18°C. Its adaptable pH range is pH 6~8, with an optimum pH of 6.6.
Occurrence pattern:
The pathogen can survive in soil, plant residues and garbage mixtures. In any soil where infected plants such as peanut, tomato, eggplant, tobacco, beefwood, eucalyptus, chrysanthemum and dahlia have been grown, as well as in soil fertilizers and water sources that have come into contact with diseased residues of the flowers, stems, roots and leaves of these diseased plants, the bacterial wilt pathogen may exist and multiply. If such soil, water or fertilizer is used to cultivate cannas, bacterial wilt will occur. The pathogen can survive in soil for more than 1 year, and only 30 days and 90 days under dry or waterlogged conditions. The pathogen mainly invades through wounds on the host. Damage from wind and rain, insect feeding and human activities all create opportunities for the pathogen to invade. Surface runoff and root-to-root contact between plants are the main routes of spread within a small area. Long-distance spread relies on diseased tuber propagation material. Generally, the disease begins in March each year, is severe from June to October, and peaks from July to September. After typhoon rain, when the atmospheric temperature is 33~35°C and the relative humidity is above 80%, if the green space is waterlogged, bacterial wilt is most likely to become epidemic.
Control methods:
1. Do not take tubers from diseased areas as propagation material. Enforce strict quarantine. If batches of diseased seedlings are found, they should be eliminated in batches.
2. Do not plant cannas in soil where bacterial wilt has occurred. If farmyard manure is to be applied, it should first be piled and composted and fully decomposed, or each square meter should be drenched with 6 kg of a 50-fold dilution of 40% formalin, then covered with plastic film for disinfection.
3. Do not cultivate or weed during the epidemic period, to avoid injuring the plants. If diseased plants are found, pull them out immediately, dig out the diseased soil, and sprinkle or drench around them with a 400~600-fold dilution of 25% Qingkuling, or a 3000~4000-fold dilution of 90% soil streptomycin, or sulfur powder. In diseased areas, it is best to drench or sprinkle the above agents once after a typhoon.
Control Methods for Canna Bacterial Wilt
In recent years, hybrid cannas planted in gardens and along roadsides in various places, with short and sturdy plant types, dark green leaves, rich flower colors and bright hues, have been deeply loved by people. However, in 1998, a devastating bacterial wilt outbreak occurred on a large scale in the green spaces of Shenzhen. Losses in various places amount to nearly 100,000 plants each year, with an incidence rate of 20~30% in diseased areas, and severe cases die in large patches, affecting the landscape.
The pathogen infects the stems and root systems of the plants. During an epidemic period, it generally takes 10~15 days from infection to death of the plant. Most infections start from the roots, though some enter through the stems. The aboveground leaves of diseased plants lose water and turn yellow, wilt and droop, and gradually black streaks appear at the stem base or on the stem. After encircling the stem, the entire plant dies. When a necrotic root or stem is cut crosswise, after a few minutes a milky white or yellowish-brown bacterial ooze exudes from the cut surface. This is the pathogenic bacterium, and it is an important basis for diagnosing bacterial wilt outdoors. If the stem is cut lengthwise, strip-like dark brown streaks can also be seen.
Occurrence pattern:The pathogen can survive in soil, plant residues and garbage mixtures. In any soil where infected plants such as peanut, tomato, eggplant, tobacco, beefwood, eucalyptus, chrysanthemum and dahlia have been grown, as well as in soil fertilizers and water sources that have come into contact with diseased residues of the flowers, stems, roots and leaves of these diseased plants, the bacterial wilt pathogen may exist and multiply. If such soil, water or fertilizer is used to cultivate cannas, bacterial wilt will occur. The pathogen can survive in soil for more than 1 year, and only 30 days and 90 days under dry or waterlogged conditions. The pathogen mainly invades through wounds on the host. Damage from wind and rain, insect feeding and human activities all create opportunities for the pathogen to invade. Surface runoff and root-to-root contact between plants are the main routes of spread within a small area. Long-distance spread relies on diseased tuber propagation material. Generally, the disease begins in March each year, is severe from June to October, and peaks from July to September. After typhoon rain, when the atmospheric temperature is 33~35°C and the relative humidity is above 80%, if the green space is waterlogged, bacterial wilt is most likely to become epidemic.
Control methods:
1. Do not take tubers from diseased areas as propagation material. Enforce strict quarantine. If batches of diseased seedlings are found, they should be eliminated in batches.
2. Do not plant cannas in soil where bacterial wilt has occurred. If farmyard manure is to be applied, it should first be piled and composted and fully decomposed, or each square meter should be drenched with 6 kg of a 50-fold dilution of 40% formalin, then covered with plastic film for disinfection.
3. Do not cultivate or weed during the epidemic period, to avoid injuring the plants. If diseased plants are found, pull them out immediately, dig out the diseased soil, and sprinkle or drench around them with a 400~600-fold dilution of 25% Qingkuling, or a 3000~4000-fold dilution of 90% soil streptomycin, or sulfur powder. In diseased areas, it is best to drench or sprinkle the above agents once after a typhoon.