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ARS Home » Pacific West Area » Wapato, Washington » Temperate Tree Fruit and Vegetable Research » Research » Research Project #433180

Research Project: Short-term Impacts of Soil Applied Pesticides with Different Modes of Action (MOAs) on the Soil Microbial Community

Location: Temperate Tree Fruit and Vegetable Research

Project Number: 2092-21220-002-01-S
Project Type: Non-Assistance Cooperative Agreement

Start Date: Jun 30, 2017
End Date: Jun 29, 2019

We hypothesize that soil application of pesticides with different modes of action (MOAs) (different Resistance Action Committee (RAC) codes) will alter microbial diversity in varied ways (i.e., in the short term, soil application of different MOAs will result in the presence of different microbial communities). The proposed objectives seek to improve the ability to manage potato by manipulating the soil microbial community in ways to promote crop health and reduce pathogen persistence in the soil. Objective 1. Characterize the microbial diversity and community composition in soil before and after application of pesticides with differing insecticide and fungicide MOAs (i.e. RAC codes). Objective 2. Determine the 1) resistance and/or 2) resilience of microbial communities to perturbation, soil application of insecticide and fungicide with different MOAs.

Field Experiment. At Hermiston Agricultural Research and Extension Center (HAREC) in Oregon and Moxee Farm in Washington, replicated field trials will be established in a randomized complete block design with four replications of each treatment. Treatments will consist of various commonly used soil applied pesticides with different modes of action (MOA) (including at least two compounds with the same MOA from each of the Insecticide Resistance Action Committee (IRAC) (e.g., Imidacloprid, Thiamethoxam) and Fungicide Resistance Action Committee (FRAC) groups. Products containing multiple pesticides may also be used as treatments to examine the interactive effects of multiples MOAs on the soil microbial community. In general, each treatment will be applied according to the label. Soil samples will be collected from each of the plots prior to pesticide treatment, and at one and five days-post pesticide application. A soil sample will consist of 10 soil cores at a depth of 12 in combined into a composite sample and mixed in a 3-gallon bucket. The composite samples will be collected within each plot. With seven treatments in the study design, including one untreated control our design would result in 84 samples per location. Soils from each plot will be stored at -80oC with RNAlater until processed for total community analysis. Microbial community analysis. Soil from each sample will be used for DNA extraction, using the Mo Bio Powersoil DNA extraction kit. Total community analysis will be used to characterize the changes to the bacterial communities throughout the experiment. The microbial community will be quantified by subjecting genomic DNA, extracted from every soil sample, to PCR amplification regions of the bacterial 16S rRNA gene that vary in length and sequencing using a coded primer approach on a next generation sequencing platform. This sequencing approach allows for the tracking of multiple individual samples being sequenced in a single lane. Sequence data generated will be used to examine if differences in the bacterial diversity and community composition relate to the MOA of the pesticide applied to each treatment. The time course experiment will be used to quantify the soil microbial community’s resistance (i.e. resistance to change) or resilience (i.e. community reestablishment) to perturbation. Next Generation Sequencing (NGS) data will be analyzed using standard protocols and analysis pipelines that have been previously described (Schloss et al. 2009). Principle component analysis (PCA) and/or ordination will be used to examine the microbial community structure among the different MOAs applied.