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POSTERS: Analytical and theoretical plant pathology

Modeling pathogen distribution in strawberry production fields with the goal of developing precision fumigation strategies.
Michael Matson - USDA ARS. Frank Martin- USDA ARS, Ross Hatlen- USDA ARS, Leah Martin- USDA ARS

In an effort to develop a fumigation strategy based on the need for controlling the pathogens present rather than a uniform application of a high rate of fumigant a study was undertaken to validate sampling approaches for obtaining accurate pathogen risk factors. We modeled the distribution of Verticillium dhaliae microsclerotia (MS) prior to fumigation in a 10 acre field in Watsonville CA. 96 sample points were arranged in a grid, and samples were collected via pooling scoops of surface soil directly over the sample “point” and scoops 5ft N, E, S, W of the point. This sampling strategy was compared with a finer strategy, where the NESW subsamples were kept separated, and additional subsamples 5ft further out were also collected. Total DNA was extracted from 0.5g soil samples, and a TaqMan qPCR assay determined the approximate number of MS/g of soil from the resulting Ct values. Counts of pre fumigated propagules ranged from ~20 MS/g, to over 300 MS/g of each pooled soil sample, and occasionally varied similarly between the subsampled samples. Eight additional samples were revisited at five timepoints following fumigation, and both V. dhaliae DNA and MS were observed, suggesting residual DNA and propagules have the potential to persist in the soil following fumigation. These observations will be overlaid with remote sensing data from drone flights and yield monitoring to find correlations between productivity, pathogen presence and disease incidence.