Persistence of trifloxystrobin and tebuconazole in banana tissues and soil under the semi-arid climatic conditions of Karnataka, India

Trifloxystrobin and tebuconazole are used for control of Sigatoka leaf spot disease of banana. This study was conducted to evaluate residue persistence of the fungicides in/on banana fruit, other edible parts and soil after spray application of the combination formulation, Nativo 75 WG, at the standard dose, 87.5 + 175 and double dose, 175 + 350 g a.i. ha⁻¹. The fungicides were extracted from banana and soil with acetone, partitioned into dichloromethane and cleaned-up using activated charcoal for trifloxystrobin and primary/secondary amine (PSA) for tebuconazole samples. The limit of quantification of the method was 0.05 mg kg⁻¹ for both fungicides. Initial residues of trifloxystrobin were 0.444 and 0.552 mg kg⁻¹ in/on banana with peel (whole fruit), which reached <0.05 and 0.065 mg kg⁻¹ after 30 days from treatment at the standard and double doses, respectively. Tebuconazole residues were 0.636 and 960 mg kg⁻¹ initially and reduced to 0.066 and 0.101 mg kg⁻¹ after 30 days. Trifloxystrobin and tebuconazole degraded with the half-life of about 11 days. Trifloxystrobin or its metabolite was not detected in the fruit pulp. Tebuconazole being systemic in nature moved to the fruit pulp which was highest on the 3rd day (0.103 and 0.147 mg kg⁻¹) and remained for 15 days. Matured banana fruit, flower, pseudostem and field soil were free from fungicide residues. For consumption of raw banana 43 days pre-harvest interval (PHI) is required after treatment of the combination formulation. Therefore application of the fungicides towards maturity stage of the fruits may be avoided.