Fireblight, Crabapple, Crablandia. One Strike...

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We were out in our Crablandia plots at the Secrest Arboretum of OSU’s Ohio Agricultural Research and Development Center in Wooster today. One mission was to check for bacterial fireblight disease on the 76 crabapple taxa in our replicated, randomized plot. This spring we had heard of and seen some fireblight, on crabapples and other related rosaceous plants such as pears elsewhere, and we have susceptible crabapples in the trials so why not here? Yet, cultivar after cultivar, early blooming and late blooming types - no fireblight. Wait, wait, we see one shoot with the tell-tale shepherd’s crook and browning to blackening leaves remaining on the fireblight “strike”. So one strike…but there were no strike twos or strike threes! 

 

Old fireblight strike from last year
Old fireblight strike on 'Silver Moon' from last year

 

The key to fireblight getting a head start to the season arrives early, if and when there is warm (above 62 degrees F), wet weather during bloom. For the most part we did not have that in Crablandia in Wooster this year and the environmental component of the disease triangle (environment, pathogen, host) was not present – so very little disease. The cultivar that had the one strike was ‘Silver Moon’, one of our latest flowering crabapples (later means there is more chance of it being warm). Remember, all disease, like all politics, is local, as per the specific environmental conditions.