2018 ASHS Annual Conference

Floricane red raspberry (Rubus ideaus) in northwest Washington is typically grown in raised beds and weeds are managed through a combination of herbicide applications and hand weeding. Late summer plantings of tissue culture (TC) raspberry are increasing in Washington because growers find improved establishment relative to traditional spring planting. However, TC transplants can be difficult to establish relative to traditional dormant roots and cane planting materials. Ongoing research has shown polyethylene (PE) and biodegradable plastic mulches (BDMs) improve weed management and promote vegetative plant growth in spring planted TC raspberry transplants. Yet, impacts of plastic mulches in late summer plantings are unknown. Plastic mulches applied in late summer need to overwinter with minimal damage, should provide weed suppression until the following spring, and should also not increase populations of root lesion nematode (Pratylenchus penetrans; RLN), a plant-parasitic nematode with a wide host range. The overall objective of this study is to develop knowledge and practical strategies to improve establishment of late summer planted TC raspberry transplants through application of PE mulch and BDMs prior to planting. Six treatments, including four BDMs, a PE mulch, and a bare ground (BG) control are being evaluated in a commercial ‘WakeHaven’ raspberry field planted Aug. 2017 in northwest Washington. Crop growth, weed suppression, mulch performance [as percent soil exposure (PSE)], soil temperature and moisture, and RLN populations were measured in 2017. Average primocane height was 5 cm greater in all mulched treatments relative to BG control 30 days after planting, but this numeric difference was not statistically significant. There were no weeds in any of the mulched treatments, whereas BG control plots were weedy (51 weeds per m²) both in Sep. and Oct. 2017. Despite lack of statistical differences, average PSE was 1.4% and 2-15% by Dec. 2017 in the PE and BDMs treatments, respectively. Mulch damage was mainly caused by farm equipment and resultant punctures were enlarged by wind. RLN populations in soil in Oct. 2017 were not different between treatments. Plant growth, RLN population dynamics, and yield data will be collected in 2018 and 2019.