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United States Department of Agriculture

Agricultural Research Service

Research Project: Determining Impact of Soil Environment and Root Function on Horticultural Crop Productivity and Quality Title: Management of Phytophthora cinnamomi root rot disease of blueberry with gypsum and compost

Authors
item Yeo, John -
item Weiland, Gerald
item Sullivan, Dan -
item Bryla, David

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 14, 2012
Publication Date: June 18, 2013
Citation: Yeo, J., Weiland, G.E., Sullivan, D.M., Bryla, D.R. 2013. Management of Phytophthora cinnamomi root rot disease of blueberry with gypsum and compost. Meeting Abstract. Meeting booklet.

Technical Abstract: Root rot disease of blueberry caused by Phytophthora cinnamomi is becoming more prevalent as a consequence of widespread adoption of drip irrigation. This creates higher moisture content in the root zone more conducive for the pathogen. Options for disease control under organic management are limited, focusing primarily on improved drainage. We evaluated soil amendment regimes for suppression of root rot disease of blueberry via greenhouse trials in pots. Peat, yard debris compost, and dairy solids compost were compared with sawdust, the grower standard. Organic amendments were incorporated into sandy loam soil at 20% v/v. Each residue was evaluated alone and in combination with gypsum (calcium sulfate) added at 5% of the total soil volume. Control soil amendment treatments included: no amendment, no amendment plus conventional fungicide soil drench, and gypsum only (no compost). We hypothesized that compost and/or gypsum would reduce phytophthora root rot in blueberry. Compost increases cellulase enzyme activity in soil, and cellulase is capable of cleaving Phytophthora cell walls. Gypsum is thought to control root rot by calcium ion inhibition of Phytophthora zoospore motility and survival. In our first greenhouse trial, organic residues had no effect on Phytophthora infection, but gypsum suppressed the severity of infection. A second trial is in progress to confirm these results. We conclude that gypsum is a promising tool for managing root rot disease of blueberry within organic production systems.

Last Modified: 10/20/2014
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