2018 ASHS Annual Conference

Floricane red raspberry (Rubus ideaus) in northwest Washington is traditionally grown in raised beds with weeds managed through a combination of herbicide applications and hand weeding. Tissue culture (TC) raspberry plantings are increasing in Washington due to the availability of new cultivars sold exclusively as TC transplants as well as traditional cultivars becoming available through TC. However, TC transplants are more difficult to establish and cost more than traditional root and cane planting materials; therefore practices that offset these higher establishment costs might be important for overall on-farm economics. The overall objective of this project is to develop knowledge and practical strategies to improve establishment of TC raspberry transplants through application of biodegradable plastic mulches (BDMs) prior to planting. Six treatments, including four BDMs, one non-degradable polyethylene (PE) mulch, and a bare ground (BG) control are being evaluated in a commercial ‘WakeField’ raspberry field planted May 2017 in northwest Washington. Crop growth, weed suppression, mulch performance [as percent soil exposure (PSE)], soil temperature and moisture, and root lesion nematode (Pratylenchus penetrans; RLN) population dynamics were measured in the 2017 season. By the end of the growing season (Oct. 2017), average primocane height and numbers were 36 cm and 5 canes/hill greater, respectively, in all mulched treatments relative to the BG control. Weed incidence was reduced in mulched plots compared to the BG control. No post-plant herbicides or hand weeding were applied to mulched plots, but hand weeding occurred three times in the BG control. PSE at the end of the year was lowest for PE (2%) and ranged from 48% to 72% in the BDM treatments. Soil temperature was on average 1.2 °C higher in all mulched treatments relative to the BG control. When volumetric water content was considered, PE had the greatest soil volumetric water content, while Organix 0.5 (a BDM) had the lowest, and the remaining treatments were intermediate. Average RLN soil and root population densities were 65 RLN/100 g soil and 123 RLN/g root in mulched treatments, and 5 RLN/100 g soil and 44 RLN/g root in the BG control; differences were not significant and plant growth was not decreased. Overall, BDMs and PE mulch performed well for commercial raspberry established as TC transplants. These data indicate that BDMs and PE mulch provide conditions that improve crop growth and weed management compared to the standard practice of herbicide application and hand weeding.