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kdwarn

Green and purple shamrocks problem - help diagnosing?

kdwarn
9 years ago

Hi,
Can anyone help me diagnose the problem with my green and purple shamrocks? For several months now, they have not been doing well. The tops of the leaves get spotted or covered in spots - white, grayish - and then they will curl and shrivel and the whole shoot dies. Sometimes, the shoots only grow a few inches before this happens, other times they will grow to their normal height. The soil doesn't seem to have fungus as far as I can tell. There used to be tiny gnats on the top of the soil, but those have been gone for quite some time. I can't tell if these spots on the leaves are tiny mites, some sort of fungus, or perhaps a virus? Any ideas of what it is?

I guess I should note that this has happened before, but then they seemed to return to normal and did really well for several months. That time I thought it was lack of light because it was during the winter, but this time it's been going on since the beginning of summer.

This post was edited by kdwarn on Tue, Sep 2, 14 at 14:41

Comments (4)

  • tapla (mid-Michigan, USDA z5b-6a)
    9 years ago

    If you have a mite infestation that bad, you should be able to see them with a magnifying glass; or if you hold a sheet of white paper under affected leaves and flick the leaves with a forefinger, the mites should fall on the paper where you'll see them moving.

    It's possible it's something fungal - maybe Botrytis (aka gray mold), or one of the many fungi in the Erysiphales order that cause powdery mildew. If you mist your plants, you should stop. If your plants are crowded, separate them and use a fan to create air movement.

    Oxalis plantings get tired. Every so often, you should let them dry completely. I used to steal my mom's away every fall & put them in the basement where they were forgotten until spring. I would remove all the soil and repot the bulbs in a fast draining soil and give them back to her around Mother's Day. They would grow like crazy until I stole them back the next year. I did that for at least 20 years until she passed.

    So, if you can part with them for a while, a cool. dry rest will bring out the best in them. There are lots of home made fungicides you can use, and you might consider using one before you let them go dry. For a while, I used MG 12-4-8 or 24-8-16 on them regularly. Eventually I discovered Foliage-Pro 9-3-6 fertilizer, which is now my 'go to' fertilizer for everything I grow. It allows you to fertilize at the lowest doses possible w/o the plant suffering deficiencies, and there's a LOT to be said for that - especially when you might be using a soil that doesn't allow you to flush the soil when you water, for fear the soil will remain soggy for so long it has a considerable negative impact on root function, or worse, causes root rot.

    Oxalis responds extremely well to a very coarse and gritty soil.

    Al

  • kdwarn
    Original Author
    9 years ago

    Good call with the piece of paper! I rubbed the leaves and stared at the flecks for a while - finally saw some moving. Thanks a bunch - going to look up how to deal with this, but definitely open to advice.

    I'll try giving them a rest sometime soon too, perhaps after they recover a bit from this.

  • tapla (mid-Michigan, USDA z5b-6a)
    9 years ago

    A 50/50 mix of rubbing alcohol and water is very effective against mites. Use it to mist every 4 days until they're gone.

    Too, mites won't be a factor if you let the plant go dry and die back. A plant's ability to defend itself is directly correlated with how robust the plant's metabolism is. Plants growing with reduced vitality are prime targets for insects and disease because their resistance is so low. After the rest and repot into a good soil, the plant's increased metabolic rate may well provide it with the defenses it needs to send the mites packing, in search of an easier target.

    Al

  • kdwarn
    Original Author
    9 years ago

    Thanks for the help! I think I'll mist all of my plants with the 50/50 and then separate out the shamrocks.