Effect of Neonicotinoids on Microbial Communities and Soil Enzymes

Neonicotinoids have long been recognized to control the substantial crop productivity losses caused by different insect pests. After the application to crops, a significant amount of neonicotinoids is lost and eventually finds its way into the soil and nearby aquatic environments. The interaction of soil-introduced insecticides affects microbial community characteristics, soil enzymes, and eventually their functioning such as the metabolism of carbon and nitrogen, in addition to undesirable effects on non-target organisms. The characteristic changes in microbial communities can be assessed comprehensively using conventional lab culturing, gene sequencing, modern metagenomics, metatranscriptomics, and metaproteomics-based approaches. The impact on microbial communities is largely determined by the dose, physicochemical characteristics, sorption, soil organic matter content, persistence, and duration of exposure. Studies by different researchers have shown contrasting effects on soil microbial community structure. Some of the applied neonicotinoid insecticides at low doses are shown to augment the microbial population, however, high doses restrict the growth. Therefore, a thorough understanding of the negative consequences resulting from the application of different neonicotinoids may help in alleviating the toxic effects on soil beneficial microbes such as plant-growth-promoting bacteria, reducing the content in crop produce, diminishing soil contamination, and minimizing health risks to humans. The present chapter has provided information pertinent to the methods of microbial community analysis, the effect of neonicotinoid application on soil bacterial and fungal communities, and finally effect on soil enzymes, associated microbiological functioning along with the future directions.