Persistence and dissipation of fluopyram and tebuconazole on bell pepper and soil under different environmental conditions

Abstract

ABSTRACT Persistence and dissipation of fluopyram and tebuconazole on bell pepper and soil was studied in the open field and in the poly-house. Application of the combination formulation, fluopyram 200 + tebuconazole 200-400SC was given to bell pepper crop simultaneously. The environmental parameters including light intensity at the two locations were recorded during the study period. A gas chromatography–mass spectrometry (GC-MS) was used for analysis of the chemicals at a limit of quantification (LOQ) of 0.01 mg kg−1. The fungicides persisted longer in the poly-house where the light intensity was 60-65% less compared to the open field. The degradation half-life of fluopyram was 7.3 days in bell pepper fruits; 13.7–15.8 days in bell pepper leaves and 29.7–31 days in soil in the open field. In the poly-house the corresponding half-lives were 9–9.3 days, 27.4 days and 38.4–40 days, respectively. Tebuconazole half-lives in the open field and poly-house were 6.1 and 7.2 days in the fruits; 11.6–15.1 and 22.3–25.3 days in the leaves; 26.8–28.8 and 32.3–36.9 days in the soil, respectively. Fluopyram benzamide, the major metabolite of fluopyram, was detected in the bell pepper fruits and leaves both in the open field and poly-house and it constituted 0.5–4.4% of the parent compound. The pre-harvest interval (PHI) for the combination formulation was 9 days in the open field and 13 days in the poly-house at the standard dose of application and at the double dose it was 15 and 20 days, respectively. Influence of light intensity leading to higher photo-degradation was concluded to be the reason for faster dissipation of fluopyram and tebuconazole in the open field.