Biology and control of Coniophora eremophila on lemon in Arizona

Abstract

A field survey of mature lemon trees showed an average of 30% of the trees with symptoms of brown heartwood rot caused by Coniophora sp. The temperature range of growth in culture for Coniophora is 15-40C with growth optimum at 30C. Vegetative incompatibility trials from one mature orchard show isolates from different trees are incompatible. In wood block decay studies, the average weight loss over 20 weeks was 5-20%. In comparison, decay studies comparing Coniophora with other brown or white rotting fungi, the other fungi decayed 4-8 times more in vitro. Cultural characteristics include simple septate hyphae, moderately growing mycelium that develop crustose brown to brownish-black patches as they mature, and negative for polyphenol oxidases. In vitro fungicide trials show that only NECTEC paste was effective in reducing decay on lemon blocks inoculated 15 weeks with Coniophora. SEM studies show mycelial fragments, pit enlargement, in radial plates, cracking and disintegration of wood.