gonebananas:

I think you are trying to fine-tune nitrogen availability far too much. If you have a fireblight problem, buy a bag of streptomycin and apply it at bloom and a week or ten days later. Fireblight will not get started, and if it doesn't get started early in the season, usually you won't see it. I dealt with fireblight on the apple trees for over 20 years, but in the 5 years I have been applying early streptomycin, I have seen absolutely none.

You can also use a whole lot of organic mulches with little fear of nitrogen overload. Things like stable manure, wood chips, or ground leaves have fairly low nitrogen levels, but still help to build the soil by adding organic matter, which it sounds like your soils need. I definately would not cut back on watering to try to control fireblight if you are in a dry summer climate. You risk stressing the trees to control a disease that should be controlled much earlier.

Don Yellman, Great Falls, VA

Thanks.

I have the streptomycin but haven't applied it yet. Most of my less-highly resistant plants (all are said to be fairly resistant) were too young to bloom this year so I skipped it, waiting until weather conditions get hotter and wetter.

I had thought of the low-N mulches (though stable manure doesn't sound low N) but was leaning against them to instead grow warm-season grass below the trees, again as a nitrogen control (an old practice from before the antibiotic age). The reason I hadn't wanted to rely on streptomycin alone is because the instruction I saw was spray at bloom and then every 5-7 days while conditions were ripe for FB, which here could be months (hot and wet). These plants will be at a site that I hope not to have to attend to weekly for much of the year.

Finally, I have seen some FB on a quince here and one pear and these showed up months after bloom. Thus I thought infection could start anytime there were young developing leaves.

Your experience is very encouraging though. I will try the streptomycin before going to any other extraordinary measures. I can always rake sawdust or leaf mulch away to plant grass if necessary.

GB, you should know that FB can easily find your blossom-free trees - one year I had 25 pear trees break out with infections before any of the trees had bloomed. The key is regular monitoring - I didn't lose a single tree because I pruned it all out just as the stems were starting to flag.

Scott

gonebananas:

Scott makes a very good point. Early sprays with streptomycin have been successful for me, but they may not be as successful for every grower in every situation.

Keeping a close eye on your trees and pruning immediately if fireblight does appear later may turn out to be just as important. Also agree with Scott that, while FB seems to prefer blossoms as an entry point, it can attack trees that are completely blossom free. I have had this happen several times.

Don Yellman, Great Falls, VA

On top of what Scott suggested, whenever you get bloom, spraying of copper formulations every three days would be cheaper than applying streptomycin and has the same effectivity.

I now use fireblight tolerant pears. If you try the Ledbetter pear, that one is truly fireblight tolerant and resistant and you wouldn't need to spray. You can load it with nitrogen and it will grow vigorously without fireblight in the middle of fireblight capital.

Of course you can control the timing of nitrogen for the rest of your pears and report back sometime. It will truly be useful.

It sounds like the # of trees isn't that large (pots mentioned) so I expect you're better just monitoring the trees and spraying antibiotics when you see the first tell tale signs on new growth. Sometimes I just nick the last 1/2" when I see the new growth turn black.

I've only ever had 5 or so Pear trees (~12-15 varieties)and have sprayed fish antibiotics (have an aquarium too) the last 6 years on the pears. I have some really susceptible early summer pears and I've really only had outbreaks when adding new bareroots orgrafts. I think they break dormancy later and are more prone to attack when the temp is higher. Once they have been sprayed twice, I've not had an outbreak on the same tree (coincidence??).

fwiw, I haven't had much need to fertilize, but used slow release fertilizers when we lived on sandy soils. The soil at the new place is almost perfect, but I have too much shade from mature trees to add many other fruits. I think the issue is more weather/temperature related than nitrogen related.

Thanks.

With the reputation here for fireblight I will likely try all these suggestions.

I will also try to find 'Ledbetter' and about a half-dozen other less common pears with reputations for surviving hot humid southern climate.

I note a few other recent advances on the FB and pears front:

http://gardenmessenger.blogspot.com/2006/09/fighting-fire-blight-fire-blight-on.html

http://gardenmessenger.blogspot.com/2006/09/another-fire-blight-resistant-pear.html