Fireblight on young pear tree

mulberryknobJuly 10, 2008

Our original pears succumbed to fireblight several years ago. We cut them out and waited two years before replanting new pears that were advertised as fireblight resistant. One of our new pears, just coming into bearing this year. 4 years after planting, has developed bad fireblight.

A month ago DH cut off every bit he could see and now there is a lot of it again. Is there any hope for our tree or should we just get out the chain saw?

The other tree, the same age but smaller because the deer stunted it's growth after planting is so far free of it.

Any suggestions anyone. We hate to spray but we will to save this tree if there is a spray out there that will kill this disease.

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Okiedawn OK Zone 7

Hi Dorothy,

Fireblight is very hard to control but there are some antibiotic sprays that can be successful when sprayed at the right time. Unfortunately, the "right time" is, I think, right at bloom time. Sometimes up to three separate sprayings are needed. Once you already have fire blight, the sprays are much less effective.

The standard spray used for pears for probably decades now is Streptomycin. Unfortunately, in many parts of the country, the bacteria that causes fireblight (Erwinia anylovora) has developed very strong resistance to streptomycin. The newer treatment is Oxytetracycline, which is marketed commercially under different names, including Mycoshield and Flameout.

Some of the latest research involves a biological control called Pesudomonas fluorescens, marketed as BlightBan A-506. It is a bacteria, I think, that attacks the fireblight bacteria. I think it it either only effective during the bloom period or most effective during the bloom period. BlightBan sprays place colonies of the Pseudomonas fluorescens bacteria on the blossoms at the same time fireblight bacteria are on the blossoms and the Pseudomonas flurorescens attacks the Edwinia amylovora.

As far as I know, no post-infection treatment has been found that is effective on trees that show symptoms of fireblight infection, so the best chance of successful treatment is to spray the trees at bud break and during blooming. Once your tree has fireblight, about all you can do is prune off 8" to 10" BELOW any visible signs of infection. One reason post-infection controls have not proved effective is because, by the time you see the symptoms of fireblight, it has done about all the damage it is going to do in the current season and has about run its course.

And, in case you're wondering if the antiobiotics are truly effective, research shows they kinda sorta are. In most test fields used in research, they kill the fireblight bacteria about half the time. In lab tests, there are somewhat higher success rates, but the higher lab test rates just aren't seen out in the "real world".

So, my gut feeling tells me that spraying now won't help much and would be a waste of money. If you can prune off all the damage now and then spray next year at the exact right times, you might be able to wipe out the fireblight on the trees on your property. However, if it is thriving on host plants that aren't treated (and which are not on your property), the fireblight-causing bacteria is carried by certain flying insects from blossom to blossom, so it is a battle you'll have to fight every year.

Dawn

    Bookmark   July 10, 2008 at 1:32PM
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mulberryknob

Thanks, Dawn, I guess it is get out the loppers again, and this time dip them in a bleach solution before each cut. Then have the spray on hand for next year. We are losing long stretches of branch--a foot or two in some cases. I sure would like to have pears again.

    Bookmark   July 11, 2008 at 10:56PM
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Okiedawn OK Zone 7

Dorothy, You are welcome. I hope you are successful in saving your trees. I love pears but have hesitated to plant them here because of the fireblight issues.

Do you remember which variety or varieties of pears you have?

Dawn

    Bookmark   July 12, 2008 at 9:44AM
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mulberryknob

I'm not very good at keeping records. I believe one of them was moonglow but don't know now if it is the affected one or not. They were both advertised as being resistant to fireblight tho.

    Bookmark   July 13, 2008 at 12:38AM
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Okiedawn OK Zone 7

I am not good at keeping records, either, and I always think I will remember which fruit trees are which....and I do, for a year or two or three. After that, it is anybody's guess. When someone asks what a tree is, I'll say
"Well, I think it is Red Haven or Red Skin, or maybe Ranger...." or "Methley. No, wait, Ozark Premier." Of course, if I go inside and do a google search, I can usually narrow it down by fruit color of the plums and the month they ripen, but I'm likely to forget it by the next time someone says "What kind of peach (or plum) is that?"

I really, really, really want to plant pears and apples here, but fear that fireblight and cedar apple rust would make it impossible to get a crop. Still, I might try it anyway. (I'm stubborn that way!)

Dawn

    Bookmark   July 13, 2008 at 10:11AM
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