1A) Impacts of Alternative Fumigation Practices and Chemistries on Root Lesion Nematodes and Plant Growth: Year 1 Results
Determine if alternative fumigant products and fumigation practices improve management of RLN in replanted red raspberry (Experiment 1).
Evaluate if modified winter cover cropping practices reduce the potential for cover crop roots to serve as a bridge for RLN in replanted red raspberry (Experiment 2).
All experiments were conducted on commercial red raspberry farms in Whatcom County, Washington.
Design: Four treatments, each applied to single-row plots (~700 ft long); replicated 4 times (16 plots total).
Treatments* were applied Fall of 2015 and include:
1. Telone® C-35 (control)
2. Telone® C-35 + tarp
3. Telone® C-35 + Vapam®
4. Dominus® biofumigant
Design: Eight treatments, each applied to 10×30 ft plots; replicated 4 times (32 plots total).
Entire field was broadcast fumigated with Telone C-35®.
Cover crop was winter wheat (purchased from CHS), seeded at 150 and 170 lbs/acre for early and late planting times, respectively.
Destruction treatments: Touchdown (41% glyphosate; 2 qt/acre) was used with Class Act (adjuvant; 2.5%) for cover crop destruction; Insecticide was Lannate® (3 pt/acre).
Treatments applied Fall of 2015 and Spring of 2016 and include:
1. Early cover crop planting; Destruction in January, – insecticide
2. Early cover crop planting; Destruction in January + insecticide
3. Early cover crop planting; Destruction in February, – insecticide
4. Early cover crop planting; Destruction in February, + insecticide
5. Late cover crop planting; Destruction in January, – insecticide
6. Late cover crop planting; Destruction in January + insecticide
7. Late cover crop planting; Destruction in February, – insecticide
8. Late cover crop planting; Destruction in February, + insecticide
*Rates: Telone® C-35 = 35 gal/acre (injected 12 and 16″ depth; 63% 1,3-D + 35% chloropicrin); Vapam® = 75 gal/acre (injected 6 and 9″ depth); Dominus® = 40 gal/acre (injected 6 and 9″ depth). Hydraulic roller helped create seal. Tarp was AEP high-barrier tarp.
Summary of Year 1 Results
Experiment 1. RLN populations in winter wheat cover crop roots were lowest in the Telone® C-35 + tarp and Telone® C-35 + Vapam® treatments (0 and 15 Pp g/root, respectively). Populations of RLN in raspberry roots sampled in June and July 2016 were the same across all treatments. Telone® C-35 + tarp was best at reducing Fusarium post fumigation, but there were no differences in Pythium. By planting, all treatments were the same for both Fusarium and Pythium. Primocane number, height, diameter, and plant vigor were also the same across all treatments.
Experiment 2. No differences in RLN or measures of plant growth (primocane number, height, and diameter) were observed.
Overall. This project and observations of the respective experiments will continue next year. To date, results suggest these alternative fumigation and cover cropping practices do not reduce RLN and soilborne disease populations by time of red raspberry planting and have no measureable effect on first year plant growth and development. Fall 2016 RLN population data may reveal different trends, as data collected from this time point tends to be more robust. Yield data will be recorded in 2017.
Acknowledgements. This project is a collaboration among Inga Zasada, Jerry Weiland, and Tom Walters. Project funds come from the Washington State Department of Agriculture Specialty Crop Block Grant program. Many thanks to our grower cooperators (Jon Maberry and Rolf Haugen), Tim Purcell of Trident Agricultural Products, and the support of the Washington Red Raspberry Commission. Additional thanks to Sean Watkinson (program technician) and Carter DeGraw (undergraduate assistant) for assistance with data collection.
1B) Update on Root Removal Projects
The primary objective of these projects is to demonstrate and evaluate the efficacy of raspberry root inoculum removal as a pre-plant management technique for reducing soilborne pathogen and pest populations in a replant situation.
Three experiments were initiated in the summers of 2015 and 2016 on commercial red raspberry farms in Whatcom County, Washington.
We compared three root removal devices for speed and efficacy of root removal. Devices tested include: Lundeby plant lifter, beach cleaner, and potato harvester.
Recap of 2015 results: The plant lifter removed the most plant material (98%), but was the slowest of the devices tested (0.25 mph). The potato harvester operated at 1.0 mph and removed 96% of the plant material, while the beach cleaner operated at 0.37 mph and removed 91% of the plant material.
To evaluate the effects of root removal on root lesion nematodes (P. penetrans; RLN) and soilborne pathogens, a split plot experiment was established in a commercial field of ‘Chemainus’ being replanted to ‘Meeker’ in Aug. 2014.
The main plot factor was fumigation (with or without, using Telone® C-35) and the split plot factor was root removal (with or without removal using a Lundeby plant lifter), replicated six times (24 plots total). Main plots were 100 x 30 ft and the split plots 50 x 30 ft in size.
Data collected include: changes in RLN and soilborne disease (Fusarium and Pythium, proxies for P. rubi) populations, plant growth, and yield.
Recap of 2015 results: 1) RLN populations returned to pre-fumigation levels by Aug. 2015; 2) Fusarium and Pythium populations were the same by planting time in Spring 2015; 3) colonization rates of root material (> 5 mm) by Fusarium and Pythium were the same six weeks after fumigation (i.e., colonization was not impacted by fumigation); and 4) no differences were observed in plant growth in 2015.
To evaluate the effects of root removal on Phytophthora root rot, a randomized complete block experiment was established in a commercial field of ‘Meeker’ being replanted to ‘Meeker’ in Aug. 2015.
Treatments were root removal or no root removal using a beach cleaner, applied to 30 x 60 ft plots, replicated 4 times (8 plots total). The entire field was broadcast fumigated with Telone® C-35 (35 gal/acre) in early October.
Data collected include: changes in P. rubi and RLN populations, as well as plant growth and yield.
In both Experiments 2 and 3, no statistical differences were found across all treatments. We have visually observed a fumigation effect between our fumigated and non-fumigated plots in Experiment 2, with plants in fumigated plots being on average taller, having a denser canopy, and numerically higher yields (Fig. 1). However, RLN and populations of Pythium and Fusarium are the same across treatments, including fumigated and nonfumigated. To date, our results from these projects do not indicate root removal will be a viable preplant management tool for management of RLN, Pythium, and Fusarium. Data on how root removal impacts P. rubi is still being generated from Experiment 3 and we will have results in the coming months.
Acknowledgements. This project is a collaboration among Inga Zasada, Jerry Weiland, and Tom Walters. Experiments 1 and 2 were funded by the Northwest Center for Small Fruits Research, while Experiment 3 is funded by the USDA—CARE program (Project #2014-09501). Many thanks to our grower cooperators (Jon Maberry and Larry Tremaine), Tim Purcell of Trident Agricultural Products, and Randy Honcoop. Additional thanks to Carter DeGraw (undergraduate assistant) for assistance with data collection.