By L.W. DeVetter and I.A. Zasada
This project is funded by the Washington Red Raspberry Commission
The objective of this project is to explore if different nitrogen rates during red raspberry establishment influences plant and root growth, root lesion nematode (Pratylenchus penetrans; RLN) populations, and subsequent damage to plants. We have observed high RLN populations in raspberry roots collected in Whatcom County on plants that display few symptoms of infestation. Many of these plantings are high input systems, leading us to wonder if nitrogen influences RLN infestations and subsequent impacts on crop growth and yield. Through this study, we will evaluate if modification of nitrogen rates during establishment impacts damage due to RLN parasitism. The end goal is to understand if nitrogen rate can be used as a post-fumigation cultural management tool in plantings with high RLN pressure or in instances where fumigation results are poor.
Justification and Background:
Root lesion nematode (Pratylenchus penetrans; RLN) is a migratory endoparasite that feeds on plant roots, including red raspberry (Rubus idaeus). RLN feeding damages roots, which reduces root functioning (water and nutrient transport), plant growth, and subsequent yields. RLN is one of the key pests in red raspberry systems in Northwest Washington. Most growers utilize pre-plant fumigation using Telone C-35® and/or Vapam® for RLN management. While in some fields RLN suppression using pre-plant fumigation has been observed to be variable to poor, there is currently a strong collaborative effort to improve pre-plant fumigation techniques. Yet, there are few tools to manage RLN in a post plant situation. This project explores how different nitrogen rates during raspberry establishment impacts RLN populations and subsequent damage to plants. We have consistently observed high RLN populations in raspberry roots collected from plants that display few symptoms of infestation. Many of these systems are well managed and high input systems, leading us to question if plant growth as impacted by nitrogen applications will enable raspberry plants to “outgrow” high RLN populations and escape damage. This project explores this question using microplots previously established at the WSU NWREC.
The experiment will be established in field microplots located at WSU NWREC in Mount Vernon, WA. There is a total of 100 individual microplots spanning five rows that were constructed in 2010 by burying 3 ft diameter polypropylene weed mat cylinders into the soil. The experimental design will be a randomized complete block with individual treatments applied to a five-microplot section per block, replicated five times (25 microplots per treatment; 1 plant per microplot). Individual microplots will be planted with tissue culture ‘Meeker’ and inoculated with RLN (approximately 250 RLN/250 g soil) at planting to simulate a field situation with moderate RLN pressure. RLN used for inoculation will be collected from root samples harvested from field sites in Whatcom County.
Four treatments differing only in total nitrogen rates will be applied to the plants, including: 0 lbs N/acre (negative control), 30 lbs N/acre, 60 lbs N/acre, and 100 lbs N/acre. Nitrogen fertilizers will include a mixture of pre-plant and liquid fertilizers. Liquid fertilizers will be applied weekly from mid-April to mid-July. We are receptive to feedback if the review committee feels the nitrogen program should be augmented so it is more representative of commercial production in Whatcom County.
Data to be collected include:
- Populations of RLN in raspberry roots and soil; determined Sept. 2017 and April and Sept. 2018
- Soil chemistry (pH, macro- and micro-nutrients) determined Sept. 2017 and 2018
- Raspberry tissue nutrient concentrations (macro- and micro- nutrients) determined the first week of Aug. 2017 and 2018
- Cumulative plant growth measured from three tagged plants per treatment section; growth will be measured monthly from March – Nov. 2017 and 2018
- Raspberry yield and fruit quality (average berry size, °Brix, and pH); measured in 2018 only
- Visual assessments of plant health and vigor, measured once per month in June, July, and Aug. 2017 and 2018.
- Root and shoot dry weight biomass (divided by floricane and primocane) from one plant per treatment plot in 2017 and 2018.
2017 Results (pdf)