actinovate for fire blight? and question about susceptibility

davidrt28 (zone 7)November 10, 2013

Hello Fruit & Orchard forum members. I'm less than 1 mile from the upper Chesapeake Bay and summer here is *humid*. Even when a cold front comes through pushing drier air in, it stays more humid in my garden than it would out in say, Frederick. When I bought this house 8 years ago there was a crabapple that would completely defoliate by mid-summer with either scab or fire blight, or both. I cut it down. Likewise, this summer, which was wetter than usual, something caused my green gage plum to completely defoliate by mid August...could have been peach leaf curl I suppose. I can't be sure in the case of that one: but I had a Sorbus get a serious case of what I _am_ sure was fire blight last summer; this summer, it did a little better but is clearly not a long-term ornamental here.

Point being the high humidity here makes these things even worse than they are in most of the mid-Atlantic. I'm surprised that when I search this forum I see very little discussion of actinovate. Anyone had success with it? I bought some in the spring but didn't get around to using it. I actually bought it to possibly control root rot on rhododendron, but wanted to investigate it further. Then a month ago I got an unsolicited endorsement from a surprising source: a PNW wholesaler of plants who said it seemed to keep down foliar rots on Ericaeae there. How do plants get foliar spots in the cool, crisp PNW? When they are in hoop houses!

So, would like to know of your experiences with actinovate. Also, any general thoughts on resistant varieties? My Prunus mume has never gotten any kind of leaf disease here. (it has even produced some fruits but I've never tried one, they are small and hard) Are Asian Rosaceae generally less susceptible because they come from a more humid climate? Should I try an Asian plum variety instead of a European one? I am too lazy to spray, generally speaking...but wouldn't mind doing a once-yearly spray of actinovate if I'm already spraying certain ornamentals.

This post was edited by davidrt28 on Sun, Nov 10, 13 at 18:29

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Scott F Smith(6B/7A MD)

David, for fireblight actinovate is not as effective as copper or streptomycin. I have not tried it due to all the studies not rating it highly enough.

For your general question.. first step is to figure out precisely what is causing you problems. For the crabapple, fireblight doesn't defoliate, it causes shoots to bend over and look dead. Defoliation is more likely from a bad case of apple scab. The most common cause of defoliation of plums is bacterial spot, but you need an accurate diagnosis before spraying. If its bacterial spot that is your problem, the Japanese plums are no better than the europeans. Its not so hard to get under control once its diagnosed, just spray copper right before leaves appear in spring and just after they fall off in fall. Every disease is different and requires a different treatment, so step one is get an accurate diagnosis. If you can't figure it out on your own feel free to post some pictures here.

Even more generally, if you are not planning on spraying much I would not expect much from apples or plums. I would either switch to figs/persimmons/mulberries, or decide you want the apples and plums and are willing to do half a dozen sprays per year.


    Bookmark   November 11, 2013 at 7:09PM
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davidrt28 (zone 7)

Thanks. Well, at least blueberries, grapes and blackberries are pretty trouble free for me. I only wanted the green gage because I've had them in Europe and they are incredibly hard to find here. I wouldn't mind if it merely functioned as an ornamental and only bore every few years, but I can't deal with a tree lhat looks dead by mid-August.

I might try one of the so-called American hybrids...

Here is a link that might be useful:

    Bookmark   November 11, 2013 at 11:46PM
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alan haigh

There's a good reason Green Gage plums are hard to find here- they crack when rain comes while they are ripening, and they rot in humidity. You may be to far south to reliably produce them, no matter how much you spray.

They can be a wonderful plum, though.

    Bookmark   November 12, 2013 at 6:06AM
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Scott F Smith(6B/7A MD)

David, you will have problems with plum curculio on any plum. If you don't spray for them you will never get any plums. If it were not for the curculio you could probably grow the American-Japanese hybrids plums without spraying. Like harvestman says, the gage plums are some of the most difficult to grow. I get only a few fruits a year on them and this is with spraying.


    Bookmark   November 12, 2013 at 8:46AM
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davidrt28 (zone 7)

Thanks Scott. That's a shame. I'm going to completely cut the tree down this weekend when it gets warmer. No sense in having it hog space anymore.

    Bookmark   November 13, 2013 at 6:24PM
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davidrt28 (zone 7)

BTW There's a relatively non-toxic treatment for these insects.

I might try that on a better plum for this climate.

Here is a link that might be useful:

This post was edited by davidrt28 on Wed, Nov 13, 13 at 18:41

    Bookmark   November 13, 2013 at 6:34PM
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Scott F Smith(6B/7A MD)

Right, thats what I use. Once you learn the ins and outs of mixing and spray timing and refreshing after rains the Surround works great. If you get an early ripening (and thus more rot resistant) Japanese-American hybrid plum you may be able to get a good harvest with spring Surround sprays only. The one other issue that has been major for me is bacterial spot, but it only requires copper in late fall and early spring to get under control. Make sure to avoid spot-prone plum varieties. Shiro has been extremely reliable for me for example. Its not tops for flavor but the thing is bulletproof in my orchard.


    Bookmark   November 14, 2013 at 9:00AM
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Scott were do you get streptomycin? I 've been looking for it since losing 6 apples and at least 1 pear to fireblight. I know it also goes by agrimycin but haven't found anyone who stocks it.

    Bookmark   November 17, 2013 at 1:10AM
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