Hydrolysis and Photolysis Kinetics, and Identification of Degradation Products of the Novel Bactericide 2-(4-Fluorobenzyl)-5-(Methylsulfonyl)-1,3,4-Oxadiazole in Water

Impact of soil type and temperature on dissipation dynamics of a new readymix formulation of halauxifen-methyl + pyroxsulam

The persistence and dissipation of a new readymix formulation of halauxifen-methyl + pyroxsulam was investigated in three soils viz. red lateritic (Soil A), coastal saline (Soil B) and black soil (Soil C) under three incubation temperatures (20, 30 and 40° C). Soil samples were fortified at 1.0 (T1) and 2.0 (T2) mg kg^- 1 doses separately for both compounds. The analytical methods showed satisfactory mean recovery, precision and linearity and therefore accepted for analysis. Both molecules followed single first-order kinetics. A significant influence of soil type on the persistence of both herbicides was observed. The order of stability of halauxifen-methyl was Soil A > B > C and for pyroxsulam was Soil B > C > A. Besides, a faster rate of dissipation of halauxifen-methyl and pyroxsulam was recorded at elevated temperatures, regardless of soil type. This research will help to understand the effect of temperature on the fate of the herbicide mixture in soils of diverse agro-climatic regions.

First report about the screening, characterization, and fosmid library construction of Xanthomonas oryzae pv. oryzae strain with resistance to Fubianezuofeng

Bacterial blight (BB), which is caused by Xanthomonas oryzae pv. oryzae (Xoo), is a common bacterial disease that seriously harms rice production in major rice-growing areas worldwide. Fubianezuofeng (FBEZF), a sulfone bactericide that contains an oxadiazole moiety, exerts good control effect on BB. In this study, FBEZF-resistant strains of Xoo were screened for the first time in the laboratory to evaluate the risk of Xoo developing resistance to FBEZF. Three strains with moderate resistance to FBEZF, were obtained and named as F1, F2, and F3, which have resistance factors (RF) of 14.69, 15.72, and 11.12, respectively. FBEZF lacked positive cross-resistance to bismerthiazol, thiodiazole copper, zhongshengmycin and phenazino-1-carboxylic acid. The growth rates of the resistant strains F1 and F2 were similar to those of the wild-type strain in nutrient broth medium, but differed in nutrient agar medium. The extracellular polysaccharide production and pathogenicity of F1, F2, and F3 were reduced relative to those of the wild-type strain. A fosmid library containing 2304 transformants was constructed based on the genome of F2, and transformants 2193 and 2202 exhibited FBEZF resistance. The results are helpful for further study on the molecular mechanism of resistance to FBEZF in Xoo.

Persistence and dissipation study of azoxystrobin, buprofezin, dinocap and hexaconazole on mango (Mangifera indica L.)

Azoxystrobin, buprofezin, dinocap and hexaconazole are widely used in crop protection of mango from flowering to harvest. Residue assessment of these chemicals on mango fruits was done following treatments at the recommended and double doses as per good agricultural practices (GAP). Mango fruit and soil sample preparation was done by QuEChERS, and analysis was done using LC-MS/MS (liquid chromatography mass spectrometry). Using these techniques, the limit of detection (LOD) determined was 1.5 μg kg^-1 and limit of quantification (LOQ) was 0.005 mg kg^-1 for all analytes. The residue levels on mango initially were 0.265 and 0.55 mg kg^-1 for azoxystrobin, 0.63 and 0.974 mg kg^-1 for buprofezin, 0.635 and 0.98 mg kg^-1 for dinocap and 0.203 and 0.35 mg kg^-1 for hexaconazole from standard and double dose treatments, respectively. The dissipation rate of the pesticides on mango fruits was about the same except for azoxystrobin, which dissipated slowly compared with others. The half-life of degradation (DT₅₀) of azoxystrobin was 10.4-12.1 days; buprofezin, 5.8-8.5 days; dinocap, 5.4-6.2 days; and hexaconazole, 4.4-6.1 days. The pre-harvest interval (PHI) based on European Union (EU) MRL (maximum residue limit) requirements were 1 day for azoxystrobin, 15 and 26 days for buprofezin, 27 and 34 days for dinocap, and 19 and 30 days for hexaconazole. The results of this study can be used to produce mango fruits safe for consumption and to meet the regulatory requirements for export of mango fruits from India.