Fusarium wilt is a devastating plant disease caused by the fungal pathogen Fusarium oxysporum. It affects many crops, including bananas, tomatoes, cucumbers, and watermelons, among others, resulting in significant economic losses. The disease is challenging to manage once established in a field; therefore, preventive measures are crucial. Effective control of this disease relies on integrating multiple management strategies, including cultural practices, chemical control, and biological control.
Fusarium Wilt Disease Management in Guava
The Causal Organism of Fusarium Wilt Disease
The causal organism of Fusarium wilt disease is a fungus called Fusarium oxysporum. This fungus can infect many plants, including guava, and has numerous pathogenic forms specific to different host plants. In the case of guava wilt, the pathogenic form is called Fusarium oxysporum f. sp. psidii.
This pathogen enters the plant through the roots and colonizes the xylem vessels, causing them to become blocked and preventing the normal movement of water and nutrients throughout the plant. This leads to wilting, yellowing, and eventually death of the plant. Fusarium oxysporum is a soil-borne fungus that can survive in the soil for several years without a host plant.
The Disease cycle of Fusarium Wilt Disease
- Survival: The pathogen Fusarium oxysporum can survive for several years in the soil and on crop residues such as chlamydospores or mycelium. The pathogen can survive on seeds, greenhouse structures, tools, and machinery.
- Primary infection: The primary infection can occur through seed-borne transmission or infection of roots at the root tip or in small wounds, such as where lateral roots branch off from the tap root. The fungus enters the plant through the roots and spreads to the xylem vessels.
- Colonization and spread: The fungus colonizes the xylem vessels and produces mycelium and conidia, which can be carried to other parts of the plant through the water-conducting system. The fungus also produces toxins, which contribute to the disease’s symptoms.
- Symptom development: As the fungus spreads through the xylem vessels, it causes the vascular system to become blocked, leading to wilting and yellowing of the leaves, stunted growth, and premature defoliation. The infected plant may also show dieback of branches and underdeveloped fruits.
Causes/Conditions Favorable for Fusarium Wilt Disease Spread in the Field.
- Stagnation of water in the guava field: Prolonged water stagnation in the guava field provides a suitable breeding ground for the Fusarium oxysporum pathogen, which can infect the guava roots and cause the disease.
- Temperature and humidity: Fusarium wilt disease in guava thrives in warm and humid conditions. The temperature ranges of 23-32°C with 76% relative humidity provide optimal conditions for the growth and spread of the pathogen.
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