Efficacy of anaerobic soil disinfestation for control of Prunus replant disease

Authors: Browne, Greg; Ott, Natalia; Poret-Peterson, Amisha; Gouran, Hossein; LAMPINEN, BRUCE - University Of California

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/7/2017
Publication Date: 1/1/2018
Citation: Browne, G.T., Ott, N.J., Poret-Peterson, A.T., Gouran, H., Lampinen, B.D. 2018. Efficacy of anaerobic soil disinfestation for control of Prunus replant disease. Plant Disease. 102:209-218. https://doi.org/10.1094/PDIS-09-16-1392-RE.
DOI: https://doi.org/10.1094/PDIS-09-16-1392-RE

Interpretive Summary: Prunus replant disease (PRD) is an important soilborne complex that suppresses root system, canopy development, and crop yields in stone fruit and nut orchards that are planted in successive generations on the same soil. PRD is adequately managed with preplant soil fumigation, but regulatory challenges may increasingly necessitate non-fumigant approaches to PRD and other replant problems, especially in California. We examined the potential of anaerobic soil disinfestation (ASD) for control of PRD under orchard conditions. In four repeated almond replant trials in sandy loam soil near Parlier, CA, ASD was implemented in late September by soil incorporation of rice bran (a proven substrate for ASD in annual cropping systems) to a 15 cm depth. Among trials, the bran was used at: (i) 20 t ha-1 with molasses at 10 t ha-1 in 3.0-m-wide “row strips”; (ii) 20 t ha-1 in 1.8-m-wide strips; or (iii) 12 t ha-1 in 1.8-m-wide strips. ASD treatment (i) was applied both with and without a preceding 3-month sudan grass rotation, whereas treatments (ii) and (iii) involved no sudan. All ASD-treated areas were covered with clear tarp and drip irrigated with 25 cm water, which initiated ASD by stimulating microbial consumption of the bran substrate. Tarps remained for 6 weeks, during which the soil was kept at or above field capacity by pulse irrigating. All trials included non-treated control and fumigation-treated treatments. ASD raised temperature and reduced redox potential in soil at 15 and 46 cm depths for 6 weeks. Fumigation and ASD treatments both nearly eradicated bioassay inoculum of Pythium ultimum in the soil before almond trees were replanted and significantly impacted almond tree root communities of fungi and oomycetes detected by sequencing rDNA ITS amplicons after planting. All fumigation treatments and ASD treatments with rice bran at 20 t ha-1, but not the bran treatment at 12 t ha-1, increased tree growth significantly and equivalently (76 to 136% tree trunk circumference increase in year 1, compared to the controls). ASD offers effective control of PRD and is worthy of further optimization and testing for management of orchard replant problems.

Technical Abstract: Prunus replant disease (PRD), an important soilborne complex that suppresses growth and productivity of replanted stone fruit and nut orchards, is adequately managed with preplant soil fumigation, but regulatory challenges may increasingly necessitate non-fumigant approaches to replant problems, especially in California. We examined the potential of anaerobic soil disinfestation (ASD) for control of PRD under orchard conditions. In four repeated almond replant trials in sandy loam soil near Parlier, CA, ASD was implemented in late September by soil incorporation of rice bran to a 15 cm depth. Among trials, the bran was used at: (i) 20 t ha-1 with molasses at 10 t ha-1 in 3.0-m-wide “row strips”; (ii) 20 t ha-1 in 1.8-m-wide strips; or (iii) 12 t ha-1 in 1.8-m-wide strips. ASD treatment (i) was applied both with and without a preceding 3-month sudan grass rotation, whereas treatments (ii) and (iii) involved no sudan. All ASD-treated areas were covered with clear tarp and drip irrigated with 25 cm water. Tarps remained for 6 weeks, during which the soil was kept at or above field capacity by pulse irrigating. All trials included non-treated control and fumigation-treated treatments. ASD raised temperature and reduced redox potential in soil at 15 and 46 cm depths for 6 weeks. Fumigation and ASD treatments both nearly eradicated bioassay inoculum of Pythium ultimum in the soil before almond trees were replanted and significantly impacted almond tree root communities of fungi and oomycetes detected by sequencing rDNA ITS amplicons after planting. All fumigation treatments and ASD treatments with rice bran at 20 t ha-1, but not the bran treatment at 12 t ha-1, increased tree growth significantly and equivalently (76 to 136% tree trunk circumference increase in year 1, compared to the control). ASD offers effective control of PRD and is worthy of further optimization and testing for management of orchard replant problems.