Efficacy Of Selected Fungicides And Bio-Control Agents In The Management Of Fusarium Wilt Of Passion Fruit

ABSTRACT

Passion fruit (Passiflora edulis Sims) is an important fruit crop in Kenya for both local and export market. Production of the crop is constrained by many diseases. Fusarium wilt caused by Fusarium oxysporum f. sp. passiflorae is one of the major disease of purple passion fruit. Yield losses due to wilt have been estimated up to 80 %. Farmers lack appropriate management strategies for the disease and the use of bio-control agents to manage the disease has not been explored. The objective of the study was to evaluate the efficacy of selected fungicides and bio-agents in order to develop an integrated disease management package for management of fusarium wilt in purple passion fruit. In- vitro tests were conducted in the laboratory to evaluate the efficacy of selected fungicides Carbendazim, Thiophanate – methyl, Azoxystrobin, and Ridomil-Mz while bio-control agents were T. harzianum and T. asperellum. The control agents were evaluated in laboratory for their effect on inhibition of colony diameter and conidia germination of F. oxysporium f. sp. passiflorae. Laboratory experiments were arranged in completely randomized design with treatments replicated four times. Control plates were without treatments. Ridomil-Mz and Carbendazim significantly inhibited colony diameter growth at p=0.05 in laboratory. T. asperellum significantly inhibited colony diameter growth at p=0.05 in laboratory compared to T. harzianum. Laboratory experiments were followed by greenhouse experiments. The fungicides and bio-control agents were evaluated as per manufacturer‘s recommendations. Purple passion fruit seedlings were raised in pots (18 cm diameter) in a greenhouse and the selected fungicides and bio-control agents were evaluated as curative as well as protectants for management of fusarium wilt. The experiments in greenhouse were arranged in split plot design with three replications per treatment. Control pots consisted of F. oxysporium f. sp. passiflorae inoculum and sterile distilled water. Plants (purple passion fruits) were assessed for disease severity and disease incidences whereas plant performance was tested on the basis of growth (height) and biomass production (shoot and root dry weights). The data obtained was subjected to ANOVA and means separated using LSD at P= 0.05. Results demonstrated that Carbendazim and Ridomil- Mz significantly reduced disease severity at p= 0.05 compared to other treatments when applied as protectants in greenhouse. Trichoderma. harzianum and T. asperellum significantly (p=0.05) led to low disease severity when applied as protectants compared to control. The two bio-agents also significantly (p=0.05) led to higher heights and higher biomass in greenhouse compared to controls. Application of Carbendazim and Ridomil- Mz as protectants as well as T. harzianum and T. asperellum can be integrated in the management of fusarium wilt of purple passion fruits in Kenya.