Fruit Canker Disease is a common and destructive fungal disease that affects guava plants. The disease is caused by the fungus Pestalotiopsis psidii, which primarily infects the fruits, stems, and leaves of the guava plant.
Fruit Canker Disease Management in Guava:
The Causal Organism of Fruit Canker Disease
The causal organism of Fruit Canker Disease in guava is a fungus known as Pestalotiopsis psidii. This fungus belongs to the family Amphisphaeriaceae and is characterized by its ability to colonize and infect guava fruits, stems, and leaves. The fungus produces small, black fruiting bodies called pycnidia, which contain numerous spores that can be disseminated by wind or water. When the spores come in contact with a susceptible host plant, they germinate and penetrate the plant’s tissue through wounds or natural openings, such as stomata or lenticels.
Once inside the plant, the fungus produces a range of enzymes and toxins that cause necrosis or death of the plant cells. This results in the formation of circular, brown, or rust-colored lesions on the surface of the fruit, which can eventually lead to the fruit’s deformation, mummification, and drop. Under favorable conditions, such as high humidity and temperatures ranging from 15-30°C, the fungus can sporulate and produce new spores, which can be disseminated to healthy plants and start a new infection cycle.
The Disease Cycle of Fruit Canker Disease
- Inoculation: The pathogen enters the host plant through wounds or natural openings, such as stomata or lenticels, on the surface of the fruit.
- Infection: Once inside the plant, the pathogen colonizes the tissue and causes necrosis or death of the plant cells. This results in circular, brown, or rust-colored lesions on the fruit surface.
- Sporulation: As the lesions progress, they may tear open the epidermis of the fruit in a circular manner, forming a crater-like appearance. In advanced stages, white mycelium consisting of numerous spores may be visible.
- Dissemination: The spores produced by the pathogen can be disseminated by wind, rain, or contact with infected plant material, thereby spreading the disease to other healthy plants.
- Secondary infection: In conducive environmental conditions, such as high humidity and temperatures ranging from 15-30°C, the spores can germinate and infect other healthy plants, starting a new disease cycle.
Causes/Conditions Favorable for Fruit Canker Disease Spread in the Field.
- Temperature: The optimal temperature for spore germination and disease development is around 30°C. Temperatures below 15°C or above 40°C are unsuitable for spore germination or disease development.
- High humidity: The disease spreads rapidly under high humidity conditions, with relative humidity above 96%.
- Rainfall: Rainfall provides moisture for the fungus to grow and spread, leading to an increased incidence of Fruit Canker Disease.
Symptoms of Fruit Canker Disease
- Minute, brown, or rust-colored circular necrotic areas on green fruits
- The lesions tear open the epidermis of the fruit in a circinate manner.
- The margin of the lesion is elevated, and a depressed area is noticeable inside.
- The appearance of the lesion is more noticeable on fruits than on leaves, giving the fruit a crater-like appearance.
- In older cankers, white mycelium consisting of numerous spores is noticeable.
- In severe cases, raised cankerous spots to develop greatly, and the fruits break open to expose seeds.
- Infected fruits remain underdeveloped, become hard, malformed, mummified, and drop.
- Sometimes, small rusty bro