Fireblight in Old Tree with No Symptoms?

General Fruit Growing
1

Hi All: Can a tree have fire blight in its system but not show any symptoms like wilting, blackened leaves?
I put thirty or so grafts on a friend’s 40 year old Red Delicious this spring and already about ten of the varieties I put on have bad fire blight and I had to cut them off. The old Red Delicious tree shows no signs of blight so I thought it was safe to topwork it.

Obviously the scions did not bloom so the blight did not come in that way. I grow these same varieties at my house and at other friends’ homes with no blight, at least this year anyway.

Varieties that blighted as soon as the grafts took include: Horse, Liberty, Black Limbertwig, Virginia Beauty, all of which I thought were pretty disease resistant.

Any ideas? Thanks.

2

It’s hard for me to picture fire blight as being latent. I’d say you’re just having a really rotten fire blight season. Here in moderately disease-free Southern California I still can lose a lot of topwork grafts on our Franken Fuji due to FB, while the tree remains healthy.

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Thanks for that information. At least I’m not the Lone Ranger on this. Is your Fuji pretty blight resistant/tolerant?

4

Fuji is susceptible and Red Delicious moderately resistant to FB.
http://www.ext.colostate.edu/pubs/garden/02907.html

So it would seem strange that Fuji could roll along while grafts on it show FB damage.

It might be possible that RD could survive while passing on FB to grafts. But agree even that sounds unlikely.

5

Fireblight on Liberty? That surprises me, but then who knows? The only thing my Liberty ever seems to get is powdery mildew (and codling moth!)

Good luck.

6

My guess is bad timing, fireblight is highly dependent on the temperature and humidity/wetness. The only tip strikes I have had this year had happened a few days ago; it could have come for you just as the grafts were getting going.

Fireblight may be able to be in the wood but it won’t give you a tip strike from that.

7

FB does pick on new succulent growth. It only attacks tissue that’s growing. Keep in my mind even a resistant tree gets hit when there is a lot of new growth and conditions are perfect with bacteria present.

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