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White chalk-like fungus/substance on plants

Posted by DrewStoddard Utah (My Page) on
Wed, May 29, 13 at 18:11

I need help identifying a white chalk-like fungus or substance of some kind that consistently seems to plague certain plants that I grow in my house. As the attached photo shows, the two palm plants are the worst affected, and they can become almost completely covered if I don't wash this chalky white substance off every couple of weeks. It does not seem to harm the plants much, and it reproduces very fast. Some plants seem to be unaffected, but I can't tell whether it's because of their position or their species.

I have tried spraying with two different kinds of commercial Fungiside (Safer Brand and Garden Safe) but neither seemed to have any effect.

Can anyone help me identify what this substance is, and how I can get rid of it?


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RE: White chalk-like fungus/substance on plants

Drew, welcome to Gardenweb!

I'd hope this is a good news/bad news situation. The bad news is that it looks like mealy bugs. The good news is that if that is what it is, an insecticide known to treat such a pest should work much better than fungicide. Do any of the spots move?

The fact that your plant has something wrong with its' health leads me to be concerned about possible root rot and/or tap water poisoning, which are somewhat related problems, but each of which could weaken a plant and make it susceptible to attack. The cause of these problems is often water sitting in a drip tray and/or soil that takes a really long time to dry out. The leaves look a little chlorotic, which would be another symptom of problems with tap water chemicals. Many people try to catch rain water, or use distilled or the condensation from a dehumidifier for at least the sensitive plants, for these reasons.

Changing the soil and removing any dead roots is also usually very helpful toward fixing these issues. From that point, watering where the excess water can drain away can also be very helpful.

Would you be able to include a pic of the whole plant?

What other plants do you have with this symptom?

If your palm is Chamaedorea elegans, I can attest it's quite sensitive to tap water chemicals, which will manifest as yellowish leaves over time.


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RE: White chalk-like fungus/substance on plants

Thank you for your very helpful response. The spots do not seem to move, but your suggestion of mealy bugs seems to be the best answer anyone has come up with so far. The way the white substance spreads does seem to indicate insect behavior. I will try an insecticide and see if that works.

On the broader subject of tap water poisoning, this is the first time I have heard of this and it is extremely useful. Several of my plants look as though they are becoming sick, and this happens after I water them with tap water for about 4-6 months. I am going to start watering them with spring water which I have delivered for drinking. I don't know if it's a pure as rainwater but at least it will be different and it will be interesting to see if there is a change.

Thanks again for all of the helpful information. I really do appreciate the time and effort. :)


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RE: White chalk-like fungus/substance on plants

You're welcome. HTH! Don't forget the dripping out is as important as the water (or what may or may not be in it.) Going outside in the shade to enjoy the summer humidity might be appreciated by the plants also. Sending good vibes!


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