Effect of Dursban 480 EC (chlorpyrifos) and Talstar 10 EC (bifenthrin) on the physiological and genetic diversity of microorganisms in soil

Abstract

This investigation was undertaken to determine the impact of the insecticides Dursban 480 EC (with organophosphate compound chlorpyrifos as the active ingredient) and Talstar 10 EC (with pyrethroid bifenthrin as the active ingredient) on the respiration activity and microbial diversity in a sandy loam luvisol soil. The insecticides were applied in two doses: the maximum recommended dose for field application (15 mg kg(-1) for Dursban 480 EC and 6 mg kg(-1) for Talstar 10 EC) and a 100-fold higher dose for extrapolation of their effect. Bacterial and fungal genetic diversity was analysed in soil samples using PCR DGGE and the functional diversity (catabolic potential) was studied using BIOLOG EcoPlates at 1, 3, 7, 14, 28, 56 and 112 days after insecticide application. Five bacterial groups (α, β, γ proteobacteria, firmibacteria and actinomycetes) and five groups of fungi or fungus-like microorganisms (Ascomycota, Basidiomycota, Chytridiomycota, Oomycota and Zygomycota) were analysed using specific primer sets. This approach provides high resolution of the analysis covering majority of microorganisms in the soil. Only the high-dose Dursban 480 EC significantly changed the community of microorganisms. We observed its negative effect on α- and γ-proteobacteria, as the number of OTUs (operational taxonomic units) decreased until the end of incubation. In the β-proteobacteria group, initial increase of OTUs was followed by strong decrease. Diversity in the firmibacteria, actinomycetes and Zygomycota groups was minimally disturbed by the insecticide application. Dursban 480 EC, however, both positively and negatively affected certain species. Among negatively affected species Sphingomonas, Flavobacterium or Penicillium were detected, but Achromobacter, Luteibacter or Aspergillus were supported by applied insecticide. The analysis of BIOLOG plates using AWCD values indicated a significant increase in metabolic potential of microorganisms in the soil after the high-dose Dursban application. Analysis of respiration demonstrated high microbial activity after insecticide treatments; thus, microbial degradation was relatively fast. The half-life of the active insecticide compounds were estimated within the range of 25 to 27 days for Talstar and 6 to 11 days for Dursban and higher doses stimulated degradation. The recommended dose levels of both insecticides can be considered as safe for microbial community in the soil.

Changes in soil microbial community and activity caused by application of dimethachlor and linuron

“…However, repeated use, overdosing, and occasional spills can introduce considerable high amounts of herbicides to soil. Moreover, in effort to extrapolate the true effect of pesticide on soil microbial characteristics, scientists usually use unrealistic doses (10 or 100-fold field rates) in laboratory assays 15 , 20 , 21 , 36 – 38 . In such conditions, significant changes of enzymatic activity, biomass or community can be observed.…”

“…To evaluate changes in soil microbial biomass, enzymatic activity and microbial community composition, the soil was incubated in plastic boxes under laboratory conditions. The design of the laboratory assay was similar to that described in our previous work 20 , 39 . Each plastic box (approx.…”

“…Evaluation of commercial formulation enables capturing changes caused by auxiliary compounds 19 . Elevated doses as high as 100-fold of field rates are commonly used in laboratory assays because it allows the observation of effects which are hindered by the natural heterogeneity of soil or when changes are too subtle to be measured when recommended dose is applied 15 , 20 , 21 .…”

The unseen effect of pesticides: The impact on phytobiota structure and functions

“…However, pesticide toxicology assessment is based only on their impact on the N mineralization test (OECD, 2000) and, thus, it does not provide information about key functions of soil microbiota (Karas et al, 2018). Despite the growing body of knowledge on the impact of pesticides on soil microorganisms, standardized methods have not been developed yet and the majority of studies have been performed at a lab-scale or using exposure levels higher than the recommended application doses (Medo et al, 2015;Wang et al, 2016). Soil microbial communities respond to organic and conventional fertilizer inputs by specific community adaptations (Hartmann et al, 2014).…”

Optimization of the Use of His6-OPH-Based Enzymatic Biocatalysts for the Destruction of Chlorpyrifos in Soil

“…The toxicity of chlorpyrifos is rather high compared to that of other organophosphate pesticides, and so is its half-life, which can be (depending on many factors) as long as 120 days [ 11 ]. The non-decomposed residual chlorpyrifos presents a great hazard [ 15 ], because this chemical affects the soil biocenosis inhabitants [ 16 , 17 , 18 ]. The residual pesticide is leached from the soil and ends up in water bodies; besides, in can be carried via forage into the organisms of agricultural animals [ 19 ] and also get into humans via the food chain or by other means, which has a negative impact on human health [ 20 , 21 ].…”