Health status of the pear tree following the establishment of Fire blight in Northern Tunisia

摘要

Pears have great importance in Tunisia for their desirable taste anc commercial value. Until 2012, the pear cultivation was protectee against fire blight by the application of a rigorous quarantine system. Fire blight, caused by Erwinia amylovora, wasoutbreak ir Tunisia in the spring of 2012 and has spread rapidly through the most important pear growing regions destroying several hundrec hectares of pear plantations. Therefore, the total pear productior has decreased from 60,000 metric tons in 2011to less than 20.00C metric tons in 2016. In this study, collected data of pear culture and surveys were carried out during four years (2012-2016) in the mair pear growing areas to evaluate the current situation of the disease in the country particularlyin the damaged regions of the lowei valley of Medjerda (Manouba, Ben Arous, Bizerte, and Beja) Samples collected from symptomatic trees were processed foi the isolation and identification of the causal agent using microbiological and molecular techniques. The results indicate that the disease had destroyed more than 5500 hectares among a total ol 8400 hectares of pear plantations area. Both provinces Manouba and Ben Arous were the most affected by fire blight disease resulting in the eradication of 350and 325 hectares of pear plantations, i.e., 100 and 98 of the total infected area, respectively. All control attempts, including sanitary measures, the application of mineral oil and copper, growth regulators and biological control have failed to limitthe spread of the disease. The presence of pathogen in the prospected regions was confirmed by pathogenicity and molecular tests, which are compatible with the symptoms observed throughout the surveys. The pear cultivation in Tunisia is threatened by fire blight due to the restriction tolerance of the available varieties and the climatic conditions favoring the staggered flowering of the species. Quarantine measures must be implemented to prevent the spread of this disease in a new disease-free areas.