Multivariate Geostatistical Modeling of Phytophthora rubi and Pratylenchus penetrans in Red Raspberry Fields

The soilborne pathogens Phytophthora rubi and Pratylenchus penetrans threaten commercial red raspberry production in the U.S. Pacific Northwest (Washington and Oregon). Due to these soilborne pathogens, the lifespan of raspberry fields has declined from over 10 years to 5–7 years. Management primarily revolves around pre-plant soil fumigation; however, regulations have made fumigation more difficult and expensive. Understanding the spatial distribution of soilborne pathogens may provide new insights into implementing targeted disease management. Therefore, this study assessed the distribution of disease severity, P. rubi, and P. penetrans in four raspberry fields in Oregon and Washington. Geostatistical analyses and spatial autoregressive modeling were performed to elucidate the interactions between soil physical characteristics and densities of P. rubi and P. penetrans, as well as disease severity, in infested fields. In general, disease severity and the pathogens were spatially clumped in the fields. Soil texture and field elevation did not consistently influence P. rubi and P. penetrans distributions in the field. Disease severity was mostly driven by P. rubi root infestation, and no significant interactions were found between P. rubi and P. penetrans in roots. This study aimed to provide a greater understanding of the ecology and epidemiology of soilborne pathogens in commercial red raspberry fields to enable the development of a targeted integrated pest management strategy.