may-jun-2020

THE ALMOND BOARD Research Finds Potential Alternative to Fumigation Prunus Replant Disease (PRD) can occur after a mature almond orchard is pulled and new trees are planted in that same soil. Though relatively common in the Central Valley, the causes of PRD are less understood than growers may assume. Greg Browne, a research plant pathologist for the USDA Agricultural Research Service and a member of the University of California (UC), Davis Department of Plant Pathology, describes PRD as “growth suppression, mediated in part by soil microbes, in successive plantings of almonds or other stone fruits.” “It varies among sites in the Central Valley,” said Browne, who has been studying PRD since 2004, thanks to funding provided by the Almond Board of California (ABC). “PRD’s impact is most pronounced in the first year or two of an orchard’s growth. It can cause severe stunting and reduces early yield — and you never get that back.” Pre-plant soil fumigation has for many years been a preferred prevention method for PRD. While in 2005 methyl bromide was phased out of most uses in the United States, alternatives such as chloropicrin (highly effective for PRD) and Telone (highly effective for nematodes, beneficial for PRD) have filled most of the void. However, those IN YOUR ORCHARD 3 4 A L M O N D F A C T S