Hi all. Last season was an especially bad fireblight season for me. Nothing fully dead, but I lost about 80% of my fruit due to blight. We did have some late season rains. But something I’ve been pondering. Can spraying your trees during fireblight prone times of the year increase the probability of fireblight strikes?
Last year was also my first year using surround. And directly after my first application of surround, the fireblight strikes were particularly bad. Do you think this is more coincidental? Or could it be that spraying at the wrong time increased the likelihood of spreading blight?
There seem to be so many unknowns with disease. Just wondering if anyone else has encountered this effect and if you have a best practice you follow. I’d like to try using surround again this year. But am a little apprehensive to spray right now.
I have been spraying pretty regular and I have not noticed more strikes per se. I have a Dorsett Golden on seedling that I am sure is a goner. And a Fuji that got shook up hard but no shoot blight. For sure blight in the new grafts has not occurred yet. About 130 of them so far.
Not an easy answer. Back in early 2000s when bonide made a combination fruit tree spray composed of all kinds of materials, I would see blight outbreaks immediately after spraying despite the fact the fruit tree spray contained an antibacterial. I do believe the Bonide mix back then was too harsh. It about made me sick to spray it even in gear.
Sprays tend to be sprayed during nice weather and it tends to be warm during those periods. Temps are everything when it comes to FB. People used to blame cold rainy weather on blight because outbreaks would follow rain, but clear warm weather also can follow a rain event. The worst blight conditions for me are trees over blooming coupled with dry warm conditions. Insects are far more active during warm dry weather and they are vectors of blight. Warm winds can also spread it.as well.
I have not noticed any issues simply using an fungicide with Carbaryl or Surround in recent years.
I don’t think spraying will cause FB or increase chance of it. Neither will Surround.
It’s pretty much as KPS said, you spray when it’s nice and the you get warm rains afterwards and then they get infected. Rain and 65 degree plus temps is the recipe for FB. If you aren’t spraying for FB chances are things are open for infection by the rain and subsequent insects going from flowers to flower.
It’s said that a single drop of ooze from a FB canker can contain millions of fireblight bacteria in that single drop. Infection of the flower takes about 10k bacteria to to actually infect the tree. The stigma is a perfect place for it to sit and multiple to that threshold. It’s amazing to me that there will be 10,000+ bacteria on the stigma.
So far in my area we’ve had some rains, but it’s always been below 60. Blooms are about over, except for some Brameley seedling trees which seem to get it late because they bloom so late and I’m no longer using streptomycin in my spray.
They do say in commercial orchards to treat trees with antibiotics after hail storms and wind storms when you have blowing sand. Basically mechanical damage let’s the pathogen in.
I looked up Seranade. Thats pretty interesting. It would be nice to put on as a buffer layer early on for FB.
Might also be a great addition to my program late in the season for fruit rots, when I try to back off chemical usage due to fruit eating time.
A long time ago we did a trial on garden mum’s with some company, where we mixed something in our soil mix. It was suppose to occupy the spaces that Phytophthora occupied on the roots so it couldn’t establish itself and hurt the mums. Never saw it go to market. Sounds like a similiar science.
What is it about rain that increases FB? Is it the water droplets carrying the blight from branch to branch, or is it higher humidity that is an ideal growing condition for the bacteria? I guess my main concern is that spraying liquid on the tree will have a similar impact as rain. But I am leaning towards spraying and trying again. The weather here this week will be in the 80’s and then will drop back down to low 70’s high 60’s. Probably done with rain for the rest of the spring/summer.
Spraying when there are flowers without antibiotic in the water will absolutely increase your fireblight risk.
Insects carry the bacteria to open flowers. Then, any rain or moisture or humidity or spray will wash the bacteria down into the flower where they infect the inside of the flower (necaries? ovaries?).
If you have open cankers or ooze, spraying can splash the bacteria around and infect young shoots, but the spray water issue is really the flowers.
Is a sticker spreader ok to mix in with Streptomycin? Seems like it could potentially negatively impact pollination. But I don’t know, thats why I am asking.
I use Regulaid as a spreader as was suggested by PSU as the proper surfactant for streptomycin. It’s an fine oil. I use Pinene as my sticker. It’s basically like Nu Film.
I don’t believe it has a negative effect on pollination. I haven’t ever seen anything written that states that it has any negative effects.
Too much streptomycin and/or Regulaid can cause your leaves to yellow.
