Hollyhock rust or a pest?

nancyk(6)June 1, 2010

Is this hollyhock rust or a pest? Thanks.

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dan_staley(5b/SS 2b AHS 6-7)

Unable to tell with that foto. Something larger than 75 x 90 plz.

Dan

    Bookmark   June 1, 2010 at 8:04PM
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jean001(z8aPortland, OR)

Perhaps you;'ll consider this nitpicking, but rust *is* a pest. Asa it turns out, "pest" is an all-inclusive term that includes diseases, insects, mites & 4- or more legged critters.

    Bookmark   June 1, 2010 at 11:46PM
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nancyk(6)

I tried 5 times to attach a photo, each time this site said it was too large. That is why the atached photo is so small.
I am trying to figure out if I should apply a fungicide or perhaps Sevin. The leaves of the plant, starting from the bottom to the top, are slowly looking like lacework.
Perhaps insecticidial soap?

    Bookmark   June 2, 2010 at 8:22PM
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jean001(z8aPortland, OR)

If it's lacework -- as in lots of holes -- something is eating it. Need to ID what it is so that can use appropriate methods. Might be working from the underside of the leaves. Handpicking always works.

That said, rust is VERY common on hollyhocks. Works from the bottom leaves upward. But once it begins, too late to spray. Instead, remove & trash affected leaves, then figure how you might increase air circulation in that area.

    Bookmark   June 2, 2010 at 8:28PM
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taz6122(N.W. AR.6b)

The photo shows lots of holes. It's an insect and as mentioned above you need to ID before treating.

    Bookmark   June 2, 2010 at 11:25PM
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nancyk(6)

Any reason to NOT spray it with insecticidial soap? I am going to remove the lower affected leaves in a few minutes.

    Bookmark   June 3, 2010 at 7:34AM
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nancyk(6)

While removing the lower leaves(which I then burned) I noticed very small worms on the upper, less-affected leaves. I removed those leaves also. So I assume the lacy leaves are from the worms, which I had not noticed before. I will dust the stalk of the plant, which is ready to bloom, with bt. I did notice some rusty, orangy patches on the stalk and some leaves, so I suppose that is another remedy.

    Bookmark   June 3, 2010 at 8:29AM
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rhizo_1 (North AL) zone 7

The 'worms' you've spotted are probably the larvae of the hollyhock (hibiscus) sawfly. This insect is NOT a caterpillar and cannot be controlled by the Bt you've applied. Bt for caterpillars should only be used when there is a serious population of very young caterpillars.

Sawfly larvae are skeletonizers, and cause that 'lacy' effect you've described. These insects can easily be removed by hand or with directed sprays of insecticidal soap. Please don't use the Sevin, which causes more harm than it can ever provide service to you in your garden.

If you Google 'hollyhock rust' you will be able to access plenty of images to compare with your 'rusty, organgy patches', as well as what to do to control it, if that is what your plant has.

    Bookmark   June 3, 2010 at 9:44AM
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nancyk(6)

It is supposed to rain this afternoon, so that will wash off the bt. I do have insecticidal soap, so I can spray that tomorrow. Does the sawfly itself do damage or just the larvae? I would prefer to not spray Sevin, we just happen to have a very old package of it somewhere, and as we are not eating the hollyhock I thought it could cover a few different pests(I did not know bt would not kill all worms above ground). I did see a larger grey insect on a leaf, it had spindly legs. I assumed it was a good insect so I let it be.

    Bookmark   June 3, 2010 at 10:35AM
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jean001(z8aPortland, OR)

The sawfly stage that damages your leaves are the "worms" you see. (They closely resemble caterpillars but aren't.) Squish; flick into soapy water; or spritz with insecticidal soap. Repeat as needed.

But gosh, now I know at least one thing we don't seem to have on the hollyhocks here in the PNW. Sawflies! (At least not yet.) But we have more than enough rust to make up for that. Especially during this very wet spring.

    Bookmark   June 3, 2010 at 2:39PM
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rhizo_1 (North AL) zone 7

Just to let you know....Sevin is not a problem only for humans. It's highly toxic to bees and other pollinators, earthworms, and a host of other beneficials.

Old containers of pesticides can be disposed of legally and don't need to be used up just to get rid of them. Contact your local recycling center or waste management department and find out about their toxic waste pick up (or drop off) policies.

    Bookmark   June 3, 2010 at 9:44PM
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taz6122(N.W. AR.6b)

For a positive ID check the legs on the larvae. If they have 5 or less prolegs they are not sawfly. If they have 6 or more they are sawfly larvae.

    Bookmark   June 3, 2010 at 9:49PM
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rhizo_1 (North AL) zone 7

Yes, the number of prolegs are an identifying feature, taz, but most folks don't know that term. You might want to explain it to someone needing an ID.

Proper ID is so important. I jumped to the conclusion that her critters are sawfly larvae because of the description of the damage ( typical for this sawfly), because of the species of plant (if you have hollyhock or other members of the mallow family, you'll often be plagued by this insect, and by nancy's use of plural when mentioning the 'worms'. Sawfly larvae are never lonely for each others' company.

Add to that your explanation of the proleg feature, and there's not much chance of a missed ID!

Here is a link that might be useful: Hibiscus (hollyhock) sawfly larvae on Google

    Bookmark   June 4, 2010 at 7:48AM
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nancyk(6)

Thanks for the link. I squished 3 sawfly this morning. And the worms are minimal, I could find none.

    Bookmark   June 4, 2010 at 11:19AM
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taz6122(N.W. AR.6b)

rhizo_1 Your post would have been much shorter had you just explained it yourself. If we were to explain everything possibly unknown by any poster we could be here all day. Once a word or phrase is given people can search the web.

    Bookmark   June 4, 2010 at 4:57PM
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dan_staley(5b/SS 2b AHS 6-7)

rhizo not prolix IMHO.

Hopefully that wasn't too wordy.

Dan

    Bookmark   June 4, 2010 at 7:30PM
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rhizo_1 (North AL) zone 7

Ah, well....I'm a born educator, what can I say? Sometimes you can just 'tell' when someone needs a little bit of extra help.

I truly think that when knowledgeable people can add to each others' posts, as so often happens in the Gardenweb, much magic happens. I learn, you learn, they learn, she and he learns, we ALL learn.

    Bookmark   June 5, 2010 at 10:58PM
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nancyk(6)

rhizo- your posts were not too long, and all above were very helpful. I check the hollyhock early morning and try to catch the evil-doers.

Nancy

    Bookmark   June 8, 2010 at 2:24PM
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