2017 ASHS Annual Conference

Root lesion nematode (Pratylenchus penetrans; RLN) is a plant-parasitic nematode that reduces growth and yield of red raspberry (Rubus idaeus) grown in the Pacific Northwest. Growers primarily manage RLN through pre-plant fumigation, but this approach leads to variable suppression and there are few resources that provide guidelines on best practices from pre- to post-plant nematode management. Public and private researchers, extension specialists, grower commissions, pesticide manufacturers, and fumigation companies have conducted and/or supported multiple coordinated and collaborative trials evaluating different techniques to improve RLN suppression. The synthesis of this research has enabled the development of a paper- and web-based decision making tool, which can be utilized by growers and field managers to make informed decisions on specific approaches to improve RLN management for a given field situation. This tool incorporates knowledge of the biology of RLN in raspberry and assists with interpretation of soil and root sample results after the decision has been made to replant a field. Interpretation depends on several factors, such as the sample (roots versus soil) and soil (sandy loam versus silt loam) type. If RLN population densities warrant treatment for a given soil type, fumigation should be implemented during the renovation process. Fumigant chemistries and their application method must be carefully selected based on soil type, production goals, and current regulations and this tool provides recommendations based on these variables. Additional recommendations are based on the current best practices and apply broadly to all field types. Tarping is advised to maximize fumigant efficacy and bed fumigation can achieve comparable results to broadcast fumigation. After fumigation, winter cover crops may be grown and this tool recommends criteria, as well as species and cultivars, that growers should consider when selecting cover crops that are adapted to the environment and less suitable as hosts for RLN. The tool reminds growers that certified disease free planting material should be used to reduce the chance of introducing pathogens, including RLN. This tool also advises on the use of post-plant nematicides, which can be effective in fields where population densities of RLN are low to moderate. Additional research is ongoing to improve management of RLN and subsequent information will add to increase the robustness of this decision making tool. However, this current version will provide a valuable resource to guide growers and field managers on how to implement targeted RLN management approaches for a specific situation.