Published 2009-12-01
Abstract
The phytophthora root rot pathogen (Phytophthora cinnamomi) (PRR) is ubiquitous in the soils of southern Florida and is the most economically important disease following exposure of avocado tree roots to fl ooded soil conditions. Research has demonstrated that properly timed foliar applications of phosphonates are effective in preventing avocado tree decline or death due to phytophthora root rot. However, there are concerns that combined foliar applications of phosphonates in conjunction with copper fungicide would be phytotoxic to leaves and fruit. To answer these concerns, field and container demonstrations were initiated to assess the risk for phytoxicity following foliar applications of phosphonate (Prophyt® or Aliette®) and copper. A grove of grafted, 3-year-old ‘Simmonds’, ‘Donnie’, and ‘Monroe’ trees was sprayed with four foliar applications of Prophyt® or Aliette® at 28- to 53-day intervals followed with foliarly applied copper 1–20 days later. No phytotoxicity to leaves, stems, or fruit was observed. Economic analysis found Prophyt® applications to be 55% less expensive than Aliette® applications.