Stem Canker Disease is a serious fungal disease that affects guava trees, causing stem canker and fruit rot: the pathogen Physalopara psidii and the imperfect stage Diplodia netalensis cause it. The disease can cause significant damage to the guava crop, resulting in reduced yields and economic losses for growers.
Stem Canker Disease Management in Guava
Causal Organism of Stem Canker Disease
The causal organism of Stem Canker Disease is a fungus called Physalopara psidii. It is a plant pathogen that infects the main branches and stems of various host plants, causing cracking lesions that can lead to wilt and death of the plant tissue. The fungus survives beneath the bark of infected plants and becomes active during favorable conditions, producing spores that can spread the disease to healthy plants.
Disease Cycle of Stem Canker Disease
- Overwintering: The pathogen survives the winter months beneath the bark of infected plants or in plant debris on the ground.
- Spring: With the onset of favorable conditions in the spring, the pathogen becomes active and begins to produce spores.
- Spore production: The pathogen produces spores called conidia, which are spread by wind or water to healthy plants.
- Infection: The pathogen’s spores infect the plant through wounds or natural openings in the bark and begin to grow and spread within the plant tissues.
- Lesion formation: The pathogen causes small, dark brown lesions on the branches and stem of the infected plant.
- Cracking: The lesions on the stem and branches can crack, causing further damage to the plant tissue.
- Wilting: As the pathogen kills the stem tissues, the affected branches will wilt and eventually die.
- Fungal perithecia: Small brown to black structures called perithecia may develop on the infected stem. These are the reproductive structures of the fungus and are visible to the naked eye.
- Spore dispersal: The perithecia produce spores called ascospores, which are released and can spread the disease to other healthy plants.
- Secondary infection: The ascospores can infect healthy plants, starting the cycle again.
Causes/Conditions Favorable for Stem Canker Disease Spread in the Field.
The rainy season favors the spread of stem canker disease, as the high moisture levels create a conducive environment for fungal growth and infection.
Symptoms of Stem Canker Disease
- Lesions: The first symptom of a stem canker disease is the appearance of small, dark brown lesions on the branches and stem of the affected plant.
- Cracking: The lesions on the stem and branches can crack, causing further damage to the plant tissue.
- Wilting: As the pathogen kills the stem tissues, the affected branches will wilt and eventually die.
- Fungal perithecia: Small brown to black structures called perithecia may develop on the infected stem. These are the reproductive structures of the fungus and are visible to the naked eye.
- Bark discoloration: The bark on the affected branches may become discolored, turning from brown to gray or black.
- Reduced growth: Infected plants with small leaves and branches may exhibit reduced growth and vigor.
- Dieback: Severe cases of stem canker disease can cause dieback, where entire branches or plant dies.
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