RE SEARCH Bacteria project completed? 10 0 1 2 3 4 5 6 7 8 9 0 4 24 168 Uren na aanbrengen smeer Drying causes the thick paste of bacteria to die within 24 to 48 hours. more effective than disinfection. Drying causes the thick paste of bacteria to die within 24 to 48 hours. However, survival in rotting tuber waste over an extended period is possible, as has been mentioned above, which means that measures remain necessary. Disinfection of the potatoes and the machinery that are infected with a thick paste of Erwinia by means of spraying disinfectants must be taken to be totally ineffective, according to the researchers. They recommend that seed potato growers clean their machinery thoroughly with water and let them dry properly, if possible with hot air. ‘This should be sufficient to get rid of the bacteria’, say Velvis and Gunnewijk. Hardly any or no effect from ozone (photo 006) From the trials with ozone, electrolysed water and UV the disinfection results are just as disappointing as those of the standard disinfectants. The researchers concluded that there was hardly any or no reducing effect of the three disinfec720 Nalidixine-resistente stam Ech Streptomycineresistente stam Ech tants on Erwinia chrysanthemi found on potato skins. For an effective external disinfection, the number of live bacteria should have been zero after treatment, but that was not proven in the tests. As the tested products do not appear to help, the project group advised researching other methods and products, whereby the focus should be particularly on controlling infections in rotting tuber waste or infected haulm remains. No pioneering outcome available yet The bacteria project may be over now, but has the problem been solved? The conclusions and recommendations of the project group all say no and they show that a great many questions have remained unanswered. Another aspect is that no real pioneering information has come forward in the fight against Erwinia in the past four years. Part of the outcome is a confirmation and underpinning of suspicions that have been present for many years, and some studies pertained to a repetition of earlier research. One could, of course, say that the situation as it was then can no longer be compared to that of today, because of all the new varieties that have been developed since, and also because of the shift to other Erwinia strains such as Erwinia chrysanthemi. From that perspective, it could be interesting to see the exact effect of all those new varieties on the development of Erwinia. How have seed potato growers reacted to that in the past thirty years and could this aspect have made the problem unsolvable? What has the influence of susceptible varieties been on the varieties over the years? But also: what is the influence of factors such as scale expansion, climate change, the technical skills and experience of the grower, improved advice and land use? Subjects, which have not been studied or expanded upon in the past four years, but may be worth looking into after all. In a word, there is still work to be done and that arouses our curiosity as to how the next Delta plan Erwinia will be able to resolve these unanswered questions. ● Leo Hanse Tests with ozone, electrolysed water and UV showed that there is hardly any, or no reducing effect from these three factors on Erwinia chrysanthemi on the potato skin. Potato World 2010 • number 1 21 Log aantal Ech per ml extract Pagina 20
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