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Updates on Red Raspberry Alleyway Cover Crop and Biofumigation Projects

Volume 5 Issue 10

Rachel Rudolph, PhD Student at Washington State University, Dr. DeVetter and Zasada’s Program

6A) Utility of Alleyway Cover Cropping in Raspberry—Results to Date

Fig. 1. Alleyway cover crop of wheat in red raspberry.


  1. Measure the effects of alleyway cover cropping in established red raspberry on:
    • Soil quality—physical and chemical
    • Root lesion nematode (Pratylenchus penetrans; RLN) population densities
    • Plant productivity (yield, fruit quality)
    • Soil microbial community structure (biological)
  2. Evaluate performance of annual and perennial cover crops in western WA red raspberry production systems


  • Experiment was established in a commercial red raspberry field in Whatcom County (Fig. 1)
  • Treatments were established in fall 2014 and 2015 and include:
    • W1: Hard, red winter wheat cv. Norwest 553
    • W2: Soft, white winter wheat cv. Rosalyn
    • O1: Winter-hardy oats cv. TAM 606
    • O2: Winter-hardy oats cv. Nora
    • G1: Ryegrass mix that included 51.25% intermediate ryegrass cv. Tetralite and 48.24% tetraploid perennial ryegrass cv. Kentaur
    • G2: Perennial ryegrass (L. perenne) mix that included
    • 43.93% ‘Esquire’, 31.44% ‘TopHat 2’, and 22.49% ‘Tetragreen’
    • T1: Triticale cv. Trical 103BB
    • T2: Triticale cv. TriMark 099
    • R: Generic cereal rye
    • Till: Bare soil (rototilled) control
    • Mow: Weedy mowed control
  • Data collected include soil bulk density, soil compaction, RLN populations in roots and soils of raspberry and cover crops, and estimated red raspberry yield


  • Cover crops are easy to establish and maintain in the alleyways.
  • Compacted soil from repeated machine passes does hinder cover crop establishment near the beds.
  • Soil with cover crops repeatedly had lower compaction and lower bulk density than bare soil, rototilled soil.
  • There is no significantly negative (or positive) effect on yield from cover crops growing in the adjacent alleyways.
  • There are differences in RLN population densities among cover crop treatments, both in the cover crop roots and in the adjacent raspberry roots.

Acknowledgements. Thank you to the Washington Red Raspberry Commission and Northwest Agriculture Research Foundation for providing partial funding. Thank you to the grower cooperator for donating land, time, and resources for this project

6B) Alternative Pre-Plant Management Practice for Root Lesion Nematode Suppression in Raspberry

Fig. 2. Ground brassica meal.


Biofumigation is an approach to soilborne pest and pathogen management that involves the use of plants primarily from the Brassicaceae family (e.g., mustards, cauliflower, and broccoli) in rotation with cash crops. Biofumigant crops contain glucosinolates (GSLs) and upon cellular disruption and hydrolysis, can release GSL-degradation products, specifically isothiocyanates. Isothiocyanates have fungicidal and nematicidal properties, and therefore may provide growers with an alternative to chemical fumigation that is less detrimental to the environment and has less regulations for application.

Brassicaceous seed meal is the material remaining after extracting the oil from mustard, canola, or rapeseed seeds (Fig. 2). The advantage of BSM over a brassica cover crop is that the application to soil is quicker and the timing of application is flexible. Although BSM does require irrigation upon incorporation,

much less water than a cover crop and no fertilizers are needed.


Compare BSM to conventional chemical fumigation, and chemical fumigation at half the recommended rate, after raspberry roots have been removed in a continuous red raspberry production system.


  • Timing: The study was initiated in Fall 2014 with the one-time application of treatments; data collection will continue through Summer 2017. Study was performed on a commercial farm in Whatcom County.
  • Design: Four treatments assigned to a single row. Each treatment plot is 30 ft x 6 ft.
  • Data collected: Root lesion nematode (RLN) population densities, raspberry growth and productivity, and soil microbial community structure.
  • Treatments:
    • BSM: Root removal followed by BSM application (Farm Fuel Inc. proprietary mix of Brassica juncea and Sinapis alba) Fall applied at 1.5 U.S. tons/ac to a depth of 6 in with a walk-behind tiller
    • Fum: Root removal followed by full rate metam sodium (Vapam®; Spring applied at 74 gal/ac at 16 in depth)
    • ½ Fum: Root removal followed by ½ rate metam sodium (Spring applied at 37 gal/ac at 16 in depth)
    • No RR: Full rate metam sodium (Spring applied at 74 gal/ac at 16 in depth) with no root removal

Conclusions to Date

  • Root removal has not been demonstrated to be effective at managing RLN populations, compared to fumigation.
  • BSM applied at a rate of 1.5 U.S. tons/ac has not been effective at suppressing RLN populations.
  • Metam sodium applied at 37 gal/ac was nearly as effective as when applied at 74 gal/ac.

Acknowledgements. Thank you to the grower cooperator for donating land, time, and resources for this project.