Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Potential and limits of acylcyclohexanediones for the control of blossom blight in apple and pear caused by Erwinia amylovora.

Abstract

Growth-regulating acylcyclohexanediones such as prohexadione-calcium and trinexapac-ethyl have been shown to be effective in controlling fire blight infections on shoots. Since blossoms represent the primary site of infection for the fire blight pathogen, Erwinia amylovora, trinexapac-ethyl and prohexadione-calcium were evaluated for their ability to reduce fire blight infection on apple and pear flowers. Field experiments and experiments under controlled conditions were conducted on apple flowers for 4 years. A reduction of up to 50% of blossom blight was observed in treated plants. In addition, treatment with trinexapac-ethyl reduced up to the 77% the percentage of fireblight-affected flowers from which disease progressed into shoots. On pear, numbers of flower infections were reduced by a quarter and flower infections leading to diseased shoots was reduced by up to 50%. Mechanisms underlying diseased reduction following treatment with the two acylcyclohexanediones was studied using a confocal laser scanning microscope combined with a gpf-labelled strain of E. amylovora. These non-invasive techniques demonstrated bacterial migration was reduced by up to 60 and 66% in apple and pear xylem, respectively.