Black Spot on Herbs

Anderson74July 11, 2013

My mint, lemon mint, oregano and thyme all have black spots all over their leaves. I am thinking it is fungal. Because I couldn't pick all of the leaves off (they are big) I cut them all down. My question is when they grow back am I risking the same thing? Do I need to treat them further?

Thank you.

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margowicz(8/9 UK)

I think you might have what roses tend to get if it comes back there several treatments for it if you want to be organic there neem oil or if you just want rid fungus clear avalible any garden center

its called blackspot if you get chives and a couple more they help prevent it

Here is a link that might be useful: blackspot and other

    Bookmark   July 12, 2013 at 7:22AM
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nickl(Z7a NJ)

Black spot is exclusively a disease of roses - it does not spread to other plants.

However, herbs do get their share of diseases. Jennifer does not say where she lives, but in this area, downy mildew and anthracnose will often occur on herbs. Both of these diseases can sometimes show as "black spots" on the leaves.

Removing infected leaves is never a bad idea, but you should also look to things like location and cultural practices that encourage diseases.

    Bookmark   July 12, 2013 at 10:28AM
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margowicz(8/9 UK)

I never knew this I thought tomatoes could suffer from it also I guess thanks in order nicki

    Bookmark   July 12, 2013 at 7:15PM
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Thanks for the advice. The herbs were about 5 years old and decent size. We live in Columbus, Ohio.

Nicki, would you suggest any natural treatments if it comes back?

    Bookmark   July 14, 2013 at 5:49PM
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margowicz - the RHS is a great source of information on anything related to horticulture. If you just type in the problem or question and 'RHS' you will find lots of advice. So if there is something you think you've read or heard you can always check it there. A large number of plant diseases and pests are species or genus specific.

Here is a link that might be useful: Black Spot of Roses

    Bookmark   July 15, 2013 at 6:35AM
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nickl(Z7a NJ)

hello Jennifer:

A disease that I didn't mention is alternaria fungus. We don't get it ourselves because we grow our herbs outdoors in good sunlight, but I have seen it . It's mainly a disease of warm, wet areas, greenhouses and similar situations. It does show up as black spotting on the leaves, and the herbs that you mention do get it if conditions are suitable.

Sorry that I can't be more help than that, but you might want to look up that disease and see what you can find.

This post was edited by nickl on Mon, Jul 15, 13 at 10:26

    Bookmark   July 15, 2013 at 9:46AM
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margowicz(8/9 UK)

thanks flora I use that all the time before I go buy a new plant now as I bought some with knowing what to expect and well I got mildew and aphids wasn't my finest hour lol

the colour of the leaf there looks some what like a rosemary I have got.

but learned it might just be lack of nitrogen

    Bookmark   July 15, 2013 at 2:55PM
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