Abstracts Category : Other

Short-term effects of organic amendments on raspberry root rathogens : Phytophthora rubi and Pratylenchus penetrans

by Naomi Hashimoto

Raspberry fields in the Lower Mainland of British Columbia are often prepared for replanting by fumigating and/or applying broiler manure in order to control soil borne pathogens such as those causing raspberry root rot. Broiler manure applications pose a threat of nitrate leaching and contamination of groundwater, while fumigation poses environmental risks because it is a broad-spectrum biocide. The aim of my research was to evaluate the effectiveness of readily available composts to reduce the impacts of plant parasitic nematodes and Phytophthora rubi and to improve plant growth. In 2013, two outdoor pot experiments using Malahat cultivar red raspberry plants were conducted with raspberry field soils naturally infested with Pratylenchus penetrans. The first experiment held during the spring compared two concentrations of two composts, two concentrations of manure, and fumigation, in the presence or absence of P. rubi and arranged in a randomized complete block design. A 72-h flooding period after P. rubi inoculation was used to facilitate P. rubi infection. The second experiment during the summer compared the same amendment treatments without P. rubi inoculation to optimize conditions for P. penetrans. Soil samples taken from each pot were analyzed for nematode populations on the day of planting and at harvest (13 weeks later). The number of shoots and the biomass of shoots and roots were assessed at the end of both experiments, while root rot ratings were performed at the end of the first experiment. P. rubi was not detected in experiment 1 due to suboptimal environmental conditions after inoculation. Broiler manure suppressed root lesion nematode populations and improved plant growth relative to the control nearly as well as fumigation in experiment 1. There was no significant treatment effect on plant growth in experiment 2. However, broiler manure and fumigation did suppress P. penetrans populations relative to the control as in the first experiment. In contrast with earlier field studies, compost treatments did not suppress nematode populations or improve plant growth relative to the control. Overall, plant vigor and nematode suppression in compost treatments were limited. Based on previous compost studies, I speculate that longer experiment periods may be needed in order to detect benefits from composting.