Identification and Controlling of Stem Bulging of Passion Fruit (Passiflora Edulis) in Sri Lanka

Abstract

Stem bulging is one of the major biological constrains of passion fruit cultivation especially in Low country wet zone areas in Sri Lanka. Green bark split as a result of bulging, discoloration of bark and also stained internal tissues are the symptoms of this stem bulging. A survey was conducted in those infected areas to find out the causal factors of passion fruit stem bulging. Soil samples were collected from disease infected and disease free locations and analyzed for soil pH, major nutrients and some micro nutrients. Examination of the internal tissues of stem showed at first inspection, looked like fungal hyphae. Microscopic observations were consistently indicated the Fusarium species association with infected tissues. Also, Passion fruit stem bulging samples were taken and dispatched to the CABI (Centre for Agriculture and Bioscience International) for further diagnosis of causal organism. The field trail - 1 was conducted at Agro ecological zone WL1a to observe the disease transmission of stem bulging from infected plants to healthy plants. The field trail – 2 was conducted at Agro ecological zone WL1a based on fungicides, insecticides and foliar fertilizer to control the stem bulging of passion fruit. The experiment was laid out in a Randomize Complete Block Design and five treatments were used with 3 replicates. The treatments were, T1-Foliar application of insecticide - Thiamethoxam 25WG 3g/10 l, T2- Foliar application of fungicide - Thiophanate methyl 70 WP 6g/ 10 l, T3- Alternative foliar application of Thiamethoxam 35 WG + Thiophanate methyl 70 WG, T4- Alternative foliar application of Thiamethoxam 25 WG + Thiophanate methyl 70WP + Albert solution (commercial formulation of nutrient mixture) 5g/10 l and T5- Control. Results numerated that, stem bulging can be transmitted from infected plant to healthy plants as a disease. Fusarium species were consistently found in bulged area of the samples tested. The lowest disease incidence was observed in Thiophanate methyl 70 WP treated plots of field trials indicating Fusarium species may be the causal factor of the problem. Insecticide applications were failed in controlling stem bulging in the field conditions. According to the CABI report No: IMI 504215 & IMI 504216, the isolation made from internal tissues and two fungal cultures were subjected for molecular identification and Gibberella fujikuroi and Fusarium sp. were identified as associate fungi of stem bulging of passion fruit.