Save my plants!

October 20, 2008 8:41 AM

Can someone help me identify this fungus/bug that's attacking my office's plants?

We have a number of different plants at work. We love them and try to take great care but over the last couple of months we've been having issues. Most of the plants have gotten strange white patches and suddenly died off after we try desperately to save them. I theorized that we were over fertilizing them but we've switched to plain water exclusively (we'd add a capful of miracl-gro once a month or so) and it remains.

Not being botanists, or even hobbyist gardeners, we are at a loss as to what this affliction is. We haven't seen bugs yet, but the white patches seem to be cocoons or fungus patches. They appear on the undersides of the leaves or on the stems. The stems turn brown and the plants wither away to disgusting horrid shadows of themselves.

I've checked out whiteflies, spider mites and mealy bugs but they don't seem the same. The patches themselves are definitely not crawling-around bugs, although it could totally be a larval/pupal stage. An image of the most affected plant we have now is here (not the greatest pic but I can take more if needed). Please help!

posted by dozo to home & garden (11 comments total)

looks like you have MEALYBUGS!!!. (the photo is a little blurry, though)
posted by pullayup at 8:46 AM on October 20, 2008

Crap, sorry, I should have read that more closely. I still think it's mealybugs, though.
posted by pullayup at 8:51 AM on October 20, 2008

Your plants are infested with cottony scale. Your picture shows them in several stages of maturity: the fluffy white ones are mature egg-laying females. They are killing your plant by sucking the sap right out of them. Left uncontrolled, they will quickly multiply and kill the entire plant and the crawling stage larvae will move to a new plant.

You can kill them with systemic pesticides or if the plants are relatively few in number, by scraping off each critter with your fingernail. There are biological controls (predatory insects) but they are ineffective indoors.
posted by jamaro at 9:07 AM on October 20, 2008

Your plants are infested with cottony scale.

Yup...scale. Insecticidal soap works well against these critters.
posted by The Light Fantastic at 10:32 AM on October 20, 2008

Thank you both for your responses. Cottony scale does look like the answer!

True to what you are saying, it has been around 5 days since I noticed them in our manager's cube and it has already nearly devastated this 6' plant.
posted by dozo at 10:43 AM on October 20, 2008

In my experience insecticidal soap doesn't work worth a damn against these things, and they spread like mad. If the hard stuff doesn't kill them I'd throw out the affected plants and soil and bleach the pots. In my experience only a scorched earth approach works.
posted by tejolote at 10:57 AM on October 20, 2008

Yeah, I've had very limited success w/ insecticidal soaps on scale. The soap (and for that matter, all topical pesticides) can't penetrate the hard waxy shell of the mature scale. What it can kill are the soft bodied and mobile larva, so if you decide to use the soap, make sure you apply it once a week for several consecutive weeks to catch all the newly hatched larva before they form their hard shells. It is best to spray the soil near the base of the plant as that is where the larva are (they hatch on the foliage and then drop to the soil, pupate and then crawl back up the plants to feed/reproduce). The downside of using soap here is too much soap in the plant's roots will harm the plant.

Systemic pesticides work better on these bastards because the plants absorb the poisons and the scale ingest the toxins along with the sap. It's not something I like doing outdoors because the collateral damage is huge to benign insects but it's a great weapon for indoor plants.
posted by jamaro at 11:13 AM on October 20, 2008 [1 favorite has favorites]

One more thing: you can make a physical barrier on the stem (assuming the afflicted plant has a distinct truck vs growing out of the soil in a clump) to catch crawlers using Tanglefoot or a ring of Vaseline on a layer of masking tape wrapped around the trunk. This will obviate the need to treat the soil and thus makes using soap a good alternative. You'll still need to spray weekly, however.
posted by jamaro at 11:20 AM on October 20, 2008

They are tough bugs to kill. Be sure to quarantine the plants that are infected - as you may have noticed - they spread like crazy. Peal off the hard bodied adults and spray the soap to kill the youngsters. I thing the barrier idea to keep them from leaving the dirt is an awesome idea. Good luck.
posted by The Light Fantastic at 11:38 AM on October 20, 2008

From your feedback we will quarantine the infested and use sprays/barriers to keep the unaffected clean. Hopefully we won't need tejolote's advice but it's good to know that starting over might have to be the next step.

Thanks all for helping us and our plants.
posted by dozo at 12:25 PM on October 20, 2008

So, it's been a while and we seem to have gotten rid of the bugs, but the plant is looking rough. We've trimmed away the dead parts, which was at least a third of the plant, and are now nursing the rest back to health.

Take that you ugly little bastards!
posted by dozo at 4:55 AM on November 20, 2008