Determining new cost-benefit guided Phytophthora propagule treatment thresholds for HLB-affected citrus

Determining new cost-benefit guided Phytophthora propagule treatment thresholds for HLB-affected citrus

Report Date: 06/01/2020
Project: 19-010   Year: 2020
Category: Horticultural & Management
Author: Evan Johnson
Sponsor: Citrus Research and Development Foundation

 HLB is known to make citrus roots more susceptible to Phytophthora root rot.  It also reduces the efficacy of chemical management of Phytophthora root rot, creating a difficult management scenario.  Current Phytophthora management recommendations are based on pre-HLB work done in the 1980s.  These three conditions raise the question of whether yield improvement from Phytophthora management is enough to pay for the management costs themselves.  The goal of this project is to develop new soil propagule density managment thresholds and recommendations for chemical management of Phytophthora root rot based on ecomonic analysis of yield responses in different soil conditions. While potential field sites have been identified, Phytophthora count testing to confirm the usefulness of the locations was delayed by COVID response, delaying plot design and treatment.  Testing and plot layout will likely happen in June allowing for first year treatments to be applied during the most significant seasons for Phytophthora, especially with the dry spring that did not favor Phytophthora development.     


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