[nafex] Organic Brown Rot Control
scott at cs.jhu.edu
Sat Mar 24 12:10:54 EDT 2012
Caren, if your trees are dormant you can hit them with a combination of oil and lime-sulphur. That is a standard dormant spray. The best time to dormant spray is just before the blossoms and leaves come out, at that point the diseases are starting to wake up and you can set them back.
Once the trees are awake you need to alternate the oil and sulphur. Note that if you can't find Saf-T-Side oil I would not use regular mineral oil, it doesn't work nearly as well. I have to mail-order it since no local place sells it; finding it in Canada may be impossible but I expect some US place would ship it to you. If you can't find anything but sulphur, just use sulphur alone, it is probably the most effective in any case. Oh one other thing about sulphur, don't spray on days above 80F, it can burn the leaves. The most important times to spray are early in the season and mid-summer. The early sprays reduce the amount of spores left over from the previous year and the later sprays protect the ripening fruits from the spores - brown rot has a sweet tooth. Brown rot can also affect shoot tips in the post-bloom period, look for what looks like drooping, melting shoot tips.
European plums are all pretty challenging for rot. The Japanese plums usually ripen earlier and that makes it easier to avoid rot on them.
On Mar 24, 2012, at 11:30 AM, Caren Kirk wrote:
> Thanks Scott.
> My worst hit trees last year were the cherries (U of Sask) and a Euro
> plum. Just prunded them yesterday and really opened up the centre of the
> cherries, which are very bush-like. I'm sure this is going to help. I
> also cut off some branches that seemed to have been compromised. I was
> very vigourous about clean up and checking for any remaining mummies.
> My peach needs some serious pruning as I let it run wild (see below) but
> as I had to hack half of it off yesterday, I'm going to go gently with
> what's remaining. It wasn't badly affected last year.
> Bought some sulphur too, so will try that sometime next week. I'm a bit
> confused about the order for spraying, would it be dormant oil first,
> followed 3-4 days after with sulphur?
> With regards to disease resistance, unfortunately up here I have to put
> hardiness at the top of my list and disease resistance second! I believ
> the cherries have quite good resistance. I have no idea if my peach is a
> resistant as it's an unknown rootstock of a reliance peach that didn't
> survive the winters up here!
> I'll look out for Serenade and Saf-T-Side Oil, I find there is so little
> choice of products around here, maybe I'm just shopping in the wrong places!
> Good job we don't get Brown Rot too bad up here!
> Thanks again,
> Caren Kirk
> St. Jerome, QC
> On 3/23/2012 12:41 PM, Scott Smith wrote:
>> Caren, brown rot can be a challenge for organic growers. You need to attack it on every level possible.
>> 1. Keep the tree healthy, well-mulched with organic matter, and regularly fed with foliar feeders such as seaweed and fish emulsion.
>> 2. Prune the trees to be very open. Open trees let in more sun which kills the disease spores. To give an idea how open peaches can be pruned, look at the "after" picture on this link:
>> 3. Regularly scout the trees for fruit with any sign of brown rot, and remove that fruit from the orchard. This may not be possible on large trees; its another reason to keep trees short!
>> 4. Sprays that can be used include sulphur, Serenade, and Saf-T-Side oil (a mineral oil with disease smothering abilities - it is thick like yogurt). Don't just start spraying when you see the rot, do a delayed dormant (with lime-sulphur), a post-bloom, and then later cover sprays. Don't spray oil for two weeks after sulphur; sulphur can be sprayed 3-4 days after mineral oil since the oil should have all evaporated in that time. Of these three I have found sulphur to be the most effective, but none of them give strong control.
>> I have used this approach for several years now and while I generally do pretty well, I still have bad years on the susceptible varieties. Speaking of varieties, I have removed the most susceptible varieties, that is another important element of brown rot control. Your climate is not as severe as mine for diseases so you may be able to control it on your existing varieties.
>> On Mar 22, 2012, at 1:58 PM, Caren Kirk wrote:
>>> Last year I had brown rot on my cherries and plums for the first time.
>>> I had not had any experience of brown rot before, so it took me a awhile
>>> to identify it. However after doing so I was pretty meticulous about
>>> removing mummies and trying to keep the areas around the trees as clean
>>> as possible.
>>> Can anyone suggest the best organic methods for controlling brown rot?
>>> Last spring I just sprayed with dormant oil. I've heard sulfur can be
>>> I'd really like to keep it under control, not only for my cherries and
>>> plums but so it doesn't spread to my other stone fruit.
>>> Caren Kirk
>>> St. Jerome, QC
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