Don't Pick That Scab!

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As a committed crabarian, I cringe along with everyone when driving into a town or walking along a street and seeing the barren, defoliated canopies of certain crabapples this summer and now into the fall. Out darn scab! (double apologies to W.S.).


Apple scab
Symptoms of apple scab on crabapple


  Yet, it need not be this way. There is a salve for scab, a cure for crabs. It is the time-proven solution not of fungicides to prevent springtime and summer scab infections by the Venturia inaequalis fungus, but the more fundamental preventive strategy of host resistance.


  Yes, the Plant Disease Triangle rears its beauteous head. Resistant varieties (more aptly put, resistant taxa) are the answer. Check these out for our Ohio Crablandia trials at:


Crablandia at Secrest Arboretum at OARDC in Wooster, Ohio


  Do these trials stand forever? Of course not. Nature is forever changing, 24/7/365 and on and on. Thus ‘Prairifire’ crabapple, demonstrating outstanding resistance for decades, was co-opted by a mutated V. inaequalis strain in the past few decades. For more perspectives, check out:


  Beckerman, J., J, Chatfield, J., and Draper, E. 2009. A 33-year evaluation of resistance and pathogenicity in the apple scab-crabapple pathosystem. Hortscience 44(3), 1-10.


  Currently ‘Prairifire’ in Ohio is by no means highly susceptible to scab; my crabarian compatriot Erik Draper and I now rate it to have “moderate” scab incidence in our Crablandia plot. But I reject the statement I heard at a program the other day that “it’s just a matter of time” before all the crabapples will become scab-scab-dogs.



Prairifire crabapple
'Prairifire' crabapple


  Not so. Different crabapples have different types of resistance genes. Not to mention that scab does not kill like a disease such as rose rosette virus on roses. All diseases are different. All of Nature is flux. Enjoy the ride and continue to enjoy crabapples, though not just any crabapple. Don’t pick those scabs!


Crabapples in the ChatScape
Crabapples in the ChatScape


  Finally, Shakespeare wills himself into today’s final quote: “One touch of nature makes the whole world kin.” Ulysses, speaking to Achilles meant something different from how I will the quote to mean, that through learning about the natural world we become one, and O. Henry had his own take, borrowing most of the quote for his own purposes, and, but…I digress.