Plant pathogen eradication: determinants of successful programs

Data from 190 plant pathogen eradication programs in the Global Eradication and Response Database (GERDA) were reviewed to identify characteristics that contributed to successful programs in 45 countries between 1912 and 2013. The most successful treatment (94%) was tissue culture, often in combination with thermotherapy to eradicate viral or bacterial pathogens from plants held in in germplasm collections. Whilst 6% of these programs had no reported outcome, there were no recorded failures of this strategy. Host removal and/or destruction was successful in 55% of the programs and was used against all the pathogen groups. The analysis was limited by the high percentage of unknown outcome results across the pathogen groups. A quarter (49 of 190) of the records contained no indication of the eradication treatment: in 43% of these cases an unknown treatment resulted in successful eradication. There were no obvious correlations between the characteristics of a pathogen (viral/viroid, bacterial/phytoplasma, fungal/oomycete or nematode) and the outcome of the eradication program. For many species there is only one record, or the taxa records were dominated by a few genera that do not represent the biological diversity of the pathogen group. No economic or other analysis was possible due to the large number of unknown result/ongoing programs and the lack of common data. Despite these limitations, GERDA is an important record of the outcomes of worldwide plant pathogen eradication programs since the second decade of the twentieth century. However, care should be exercised when extrapolating from these records to formulating responses to new taxa as pathogens emerge and/or adapt to new plant hosts as the biology of plant pathogens is extremely variable and this diversity is not represented by the records in the database.