2019 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. Growers find establishing tissue culture (TC) transplants using this traditional method often results in reduced plant growth and yield, as well as poor weed management. Because TC transplants are increasingly being utilized by growers and cost more than traditional cane and root planting materials, growers are in need of new practices that improve TC plant establishment, weed management, and productivity. The overall objective of this project was to develop knowledge and practical strategies to improve establishment and yield of raspberry established as TC transplants using polyethylene (PE) and biodegradable plastic mulches (BDMs). Six treatments were established in May 2017 in a commercial ‘WakeTMField’ raspberry field in northwest Washington. Treatments included one PE mulch, four BDMs (BASF 0.5, BASF 0.6, Novamont 0.5, and Novamont 0.6), and a bare ground (BG) control, which is growers’ standard practice. Cumulative weed growth, root lesion nematode (Pratylenchus penetrans; RLN) population densities, soil temperature and moisture, cumulative primocane growth, and fruit yield were evaluated from May 2017 through Sept. 2018. Overall, weed incidence was reduced from May to Nov. 2017 and soil temperature was increased 1.5 °C from May to Sept. 2017 in mulched plots compared to the BG control. In Sept. 2018, RLN population densities were greater in soils covered with PE mulch than Novamont 0.5 (350 and 116 RLN/100 g soil, respectively) and were greater in raspberry roots from plots treated with PE mulch than BASF 0.6 and the BG control (2605, 430, and 692 RLN/g root, respectively). By the end of the first growing season (Oct. 2017), average primocane height and numbers were 36 cm and 5 canes/hill greater, respectively, across mulched treatments relative to the BG control. Average fruit yield in 2018 was 34% greater in the mulched treatments than the BG control. Overall, PE mulch and BDMs improved weed management and TC raspberry growth and yield compared to the standard practice of BG cultivation.