Control trees were not treated at all.įlower clusters were counted at the beginning of the experiment (full bloom) to get the total for each tree. The first application took place three hours after inoculation of trees with E. Inoculated middle trees were non-treated. 150 ml per tree (corresponds to 500 liters per hectare) and half of the recommended amount of plant protection product to account for small crown sizes in this field experiment. Plant protection products were applied using a motorized backpack sprayer (Birchmeier Sprühtechnik AG, Stetten, Switzerland) applying approx. The plant protection products LMA and BlossomProtect TM used in this study are commercially available in Switzerland via Omya and Andermantt Biocontrol, respectively. The dates of applications of treatments are listed in Table 1 and the treatments for the experiment are presented in Table 2. Inoculated trees showed no symptoms during flowering yet but when flower clusters were counted for disease incidence rating on May 25 th those inoculated trees were in bad condition. As flowers last for only a few days newly opened flowers continuously serve as new inoculum source. A bumblebee population big enough to pollinate our filed site was placed into the experimental site allowing pollination and inoculation of the non-inoculated trees and their newly opened flowers with Erwinia amylovora on the experimental trees. Bacterial cells were washed off and diluted to the respective concentration using a 0.8% NaCl solution. amylovora stains were grown on King’s B media in Petri dishes for 48 h at 28 ☌ in an incubator. amylovora (Ea 66116, Ea 66035 and Ea L 6) isolated from Malus. Nearly at full bloom, the middle tree in each block was sprayed with 135 ml of a 1 x 10 9 cfu/ml suspension of a 1:1:1 mixture of three strains of E. The purpose of this study was to determine efficacy of several non-antibiotic plant protection agents against fire blight on apple trees of the cultivars ‘Gala Galaxy’ and ‘Ladina’ in an outdoor, enclosed field site. One of those fire blight tolerant cultivars is ‘Ladina’, a breed from the research institute Agroscope in Wädenswil, Switzerland (Kellerhals et al. In this context, also tolerant cultivars will become of more importance to apple production (Sundin et al. Up to date there is authorized products available showing partial efficacy only (Reininger et al. As no antibiotics have been allowed in pip-fruits production in Switzerland from 2016 on, effective alternative plant protection strategies against fire blight are needed as stated by Sundin et al. However, fire blight will still be a major concern in pip-fruits production as it is one of the most devastating bacterial diseases. With the exception of the protected zone (canton of Valais), fire blight is no longer subject to notification or control obligations. These plants must still be free from fire blight if they are intended for commercial use (agricultural fruit production, ornamental plants). In 2018, the European and Mediterranean Plant Protection Organization (EPPO) recommended regulation of the bacterium as a regulated non-quarantine pest (RNQP) on known host plant products ( Malus, Pyrus, Cydonia, Sorbus etc.). Owing to its distribution in Switzerland, fire blight no longer meets the criteria for regulation as a quarantine organism (exception: protected zone in the canton of Valais). 2005) with a peak in 2007/2008 and incidence declining ever since. The first fire blight incidence in Switzerland was observed in 1989 around Lake Constance on Cotoneaster spp. Erwinia amylovora is a Gram-negative bacterium causing fire blight within the Rosaceae family on crops such as apple, pear, and quince (Vanneste 2000 Van der Zwet et al. Blossom cluster infection rates following different plant protection treatments did not differ significantly from each other in ‘Gala Galaxy’ whereas they did in ‘Ladina’.įire blight is a devastating disease affecting pome fruit production. ‘Ladina’ showed less fire blight blossom cluster infection in untreated and treated plants compared to ‘Gala Galaxy’. Four different treatment strategies, including an untreated control, were tested on both cultivars after inoculation with Erwinia amylovora. A plant protection product efficacy trial against fire blight with the susceptible cultivar ‘Gala Galaxy’ and the tolerant cultivar ‘Ladina’ bred at Agroscope was set up at the Agroscope Steinobstzentrum Breitenhof in 2018. In this context, fire blight tolerant cultivars become of higher importance to control the disease. As antibiotics are not allowed against fire blight in Switzerland, optimization of alternative plant protection strategies is required. Fire blight is a devastating disease of apple, pear and quince caused by the Gram-negative bacterium Erwinia amylovora.
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