Anaerobic soil disinfestation as an alternative to soil fumigation for management of Prunus replant disease: effects on tree growth and yield

Authors: Browne, Greg; Ott, Natalia; Poret-Peterson, Amisha; LAMPINEN, BRUCE - University Of California, Davis; METCALF, SAMUEL - University Of California, Davis; YAGHMOUR, MOHAMMAD - University Of California - Cooperative Extension Service; HOLTZ, BRENT - University Of California - Cooperative Extension Service; CULUMBER, MAE - University Of California - Cooperative Extension Service; BRAR, G - University Of California - Cooperative Extension Service; DOLL, D - University Of California - Cooperative Extension Service

Submitted to: Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2018
Publication Date: 10/31/2018
Citation: Browne, G.T., Ott, N.J., Poret-Peterson, A.T., Lampinen, B.D., Metcalf, S.G., Yaghmour, M.A., Holtz, B.A., Culumber, M., Brar, G., Doll, D.A. 2018. Anaerobic soil disinfestation as an alternative to soil fumigation for management of Prunus replant disease: effects on tree growth and yield. Acta Horticulturae. 1219:287-294. https://doi.org/10.17660/ActaHortic.2018.1219.44.
DOI: https://doi.org/10.17660/ActaHortic.2018.1219.44

Interpretive Summary: Growth and yield of successive almond plantings are suppressed by Prunus replant disease (PRD), a poorly understood soilborne disease complex that can occur even in the absence of tree-damaging nematodes. Preplant soil fumigation (SF) prevents PRD but is increasingly regulated, so alternatives are needed. In 2013 and 2014, we established ongoing almond orchard replant trials near Parlier, CA to examine anaerobic soil disinfestation (ASD) as an alternative to SF for control of PRD. After old orchard removal, ASD was implemented in September by incorporation of rice bran (a powder-like carbon source that is a byproduct of rice milling) to a 15 cm soil depth; rice bran was applied at 12 to 20 t ha-1, with and without molasses and with and without a preceding cover crop of sudan grass. All ASD-treated areas were covered with clear tarp (to retain moisture, soil gases, and solar heat) immediately drip irrigated with 25 cm water (to facilitate microbial use of the carbon), and irrigated for 0.5 to 1.0 h (0.2 to 0.5 cm) per day afterwards. Tarps remained and intermittent irrigation persisted for 6 weeks. All trials included non-treated control and standard fumigation treatments. Compared to the control, SF and ASD treatments with rice bran alone at 20 t ha-1 increased tree growth and yield through growing year 4 significantly and equivalently. ASD can be as effective as SF for preventing PRD and is worthy of further optimization and testing.

Technical Abstract: Growth and yield of successive almond plantings are suppressed by Prunus replant disease (PRD), a poorly understood soilborne disease complex that can occur even in the absence of phytopathogenic nematodes. Preplant soil fumigation (SF) prevents PRD but is increasingly regulated, so alternatives are needed. In 2013 and 2014, we established ongoing almond orchard replant trials near Parlier, CA to examine anaerobic soil disinfestation (ASD) as an alternative to SF for control of PRD. After old orchard removal, ASD was implemented in September by incorporation of rice bran to a 15 cm soil depth; rice bran was applied at 12 to 20 t ha-1, with and without molasses and with and without a preceding cover crop of sudan grass. All ASD-treated areas were covered with clear tarp, immediately drip irrigated with 25 cm water, and irrigated for 0.5 to 1.0 h (0.2 to 0.5 cm) per day afterwards. Tarps remained and intermittent irrigation persisted for 6 weeks. All trials included non-treated control and standard fumigation treatments. Compared to the control, SF and ASD treatments with rice bran alone at 20 t ha-1 increased tree growth and yield through growing year 4 significantly and equivalently. ASD can be as effective as SF for preventing PRD and is worthy of further optimization and testing.