2017 ASHS Annual Conference

Washington produces the majority of red raspberry (Rubus idaeus) for processing in the United States. Although total acreage of red raspberry has increased in Washington, crop longevity has decreased. The decline has been partially attributed to plant-parasitic nematodes. The most common plant-parasitic nematode in Washington red raspberry is Pratylenchus penetrans. Soil fumigation is a common management practice for P. penetrans, but efficacy is inconsistent and there are strict regulations regarding application; therefore, alternatives are needed. A three-year study is being conducted in a renovated commercial ‘Chemainus’ red raspberry field with a history of P. penetrans and other soilborne issues to evaluate Brassicaceous seed meal (BSM) soil amendment combined with root inoculum removal (RR) as preplant alternatives to soil fumigation. Treatments were applied once prior to planting and included: Brassicaceous seed meal at 3.4 t/ha with root removal (BSM+RR), soil fumigation using metam sodium at 692 L/ha (industry standard rate) with root removal (Max Fum+RR), soil fumigation using metam sodium at 346 L/ha with root removal (Min Fum+RR), and soil fumigation using metam sodium at 692 L/ha without root removal (Max Fum–RR; control). Data collected included: P. penetrans population dynamics in soil and roots, microbial (bacterial and fungal) communities in soil, raspberry vegetative growth, estimated yield, and fruit quality. Population densities of P. penetrans in soil and roots were significantly higher in BSM+RR than in Max Fum+RR and Max Fum–RR during the first two years of the study. Root removal did not affect P. penetrans densities as there were no significant differences between Max Fum+RR and Max Fum–RR. Root removal and BSM have not dramatically altered the soil microbiome compared to other treatments. The only difference among treatments was observed in the first spring after treatment when BSM+RR displayed differences in bacterial soil populations compared to the other treatments; this difference did not persist into the next sampling date. The most noticeable differences in bacterial and fungal soil populations were due to season, not treatment. There were no significant differences in raspberry vegetative growth the first summer after planting. The second summer after planting, there were no significant yield or fruit quality differences among treatments. This study is ongoing, but current data show BSM amended to soil at this experimental rate and root removal are not effective in reducing P. penetrans population densities, and BSM only has short-term impacts on the soil microbiome in red raspberry.