Wednesday, February 10, 2010

Unpretty pictures: spider mites and scale

WCW told me once that if you want to, you can overwinter Hibiscus by letting them go dormant: you stick them somewhere cool, let all the leaves drop, and then only give them just enough water to get by until the spring. And then in the spring you put them outside and they leaf out quickly and then you go on.

It seemed like a sound enough idea, and WCW said she'd done it herself, but I wasn't quite ready to commit to it. I figured if I could keep them growing and flowering happily through the winter, then there was no reason not to, so I'd only let them defoliate if it turned out that I couldn't keep them growing happily.

So I stuck them in front of a small window in the basement, and waited to see what would happen.

For the most part, nothing happened. Some sporadic blooms at first, then they settled down and just sat there. I gave them full, thorough waterings when the soil got dry, but they didn't seem to be doing anything with it.

Then, beginning in maybe mid-December, specific branches would defoliate rapidly from time to time. Like, everything would be fine, and then suddenly all the leaves on one branch would go yellow and drop overnight, and the house would rattle as all the leaves hit the floor at once.

There didn't seem to be anything wrong with the plant otherwise: I saw a little webbing, but it looked like fairly coarse webbing, the kind that spiders make cobwebs from, and they were in the basement, where there are often spiders, so I didn't suspect spider mites at first. Plus I didn't actually see any mites, ever. But it kept happening, and I got kind of worried. Plus it sucks to get woke up in the middle of the night by the house rattling because your Hibiscus just had a massive defoliation.

Maybe I didn't want to let them go dormant after all. Maybe they were defoliating from lack of light, and if I just put them somewhere brighter, this would all stop.

So. They came out of the basement to the living room, and I gave them a spot on the floor near the big window. Plenty of light there. (Also a heat vent, but -- not a very big one! And it wasn't blowing directly at the plants!) Looked the plants over, didn't see any webs or any mites.

Imagine my surprise when a whole branch defoliated again, and, upon examination, turned out to be completely swarming with spider mites.

This is much more terrifying full-size. You can actually make out individual little legs on one of them. [shudder]

Then imagine my depression, frustration and rage. Next, imagine my inebriation, as I drank to try to forget about the mites.

(You're really very good at imagining my mental states! Good job!)

So. Both Hibiscus got a prolonged bath: dish soap, shower, more soap, more shower, and now they're back in the basement again. Where, to their credit, no branches have gone suddenly nude again. But still. Spider mites are despicable. In that I am completely able to despic them. I despic them so hard, y'all.

So that was a bummer. Then, a few days after the Hibiscus returned to the basement, I was watering the big purple Neoregelia when I noticed some spots on the leaves that rubbed off, when I tried to rub them off. Which is a bad sign.

Roundish green dots: part of the natural variegation. Roundish tan dots: scale. White crusty stuff toward the right side of the picture: mostly hard-water spots, I think. Though there could be some immature scale running around in there, I'd never know.

Further inspection revealed that I had scale. And they were everywhere. Leaf surfaces, leaf undersides, the inaccessible spaces at the base of leaves -- everything. It didn't appear to be too far gone, but it was still a surprisingly advanced infestation to be catching for the first time.

The long-term solution was to add imidacloprid granules to the soil. I don't know if this will necessarily help, but I had them already, and in theory they should work. Eventually. (I have yet to be particularly impressed with systemic pesticides, actually. This is maybe something we could discuss in the comments.)

The short-term solution was to get a wet paper towel or two, or ten, or fifty, and try to wipe off as many of the bastards as I could. The only problem with that is -- well, look up at the first Neoregelia picture again. See the spines all along the leaf margins? Yeah. They're actually kind of sharp. And pieces break off in your skin sometimes. So it's not that easy to get a hand down in there, never mind trying to do any serious leaf scrubbing once it's in.

So that was also a bad day. I haven't had any issues with scale in something like ten years. (I bought a Caryota mitis, fishtail palm, without noticing that it had a serious scale problem. I kept waking up to find the floor beneath it sticky, but somehow didn't put it together that there might be a bug problem for a really long time. When I did figure it out, the plant was thrown away.) I have little itchy cuts all over both hands, and down the back of my right arm, and this is something I'm going to have to do repeatedly for a while.

The slightly-raised tan circles are, again, scale. The small, white, elongated things scattered around them are probably baby scale. The babies are actually so small that I can't see them with my naked eye; I can only see them after taking a picture, uploading it to the computer, and looking closely at it.

For some plants, I'd just throw the thing out, rather than try to undertake an extermination program. I'm willing to try extermination in this case because the plant would be expensive to replace, I've already had it a long time, and the scale doesn't appear to have done much permanent damage to the plant yet. It has spread to one other plant, also a Neoregelia, but as far as I can find (and I looked pretty hard at everything in the vicinity) it's only the one, and the infestation on the second plant was very, very light. So I'm sort of optimistic that this can be dealt with in a way that permits me to keep the plant.

And it could always be worse. It's not mealybugs.

Still, though. Depressing.


Ivynettle said...

So you have the same "pets" I do. I've given up on ever getting the scale off the Schefflerea arboricola or the lemon tree... neem oil seems to do a rather good job of killing them, but I'm just not disciplined enough to spray them regularly to kill the next generations, too.
And the spider mites have returned, too. It's good to know I'm not the only one who doesn't notice them until it's too late - I had to throw out my Mimosa pudica because I didn't think of mites when it started dropping leaves. But at least I noticed them early on on the rest of the plants (I actually bought myself a magnifying glass last year for spider mite inspections).

Oh, and of course: Thanks for your comment on my blog!

Plowing Through Life (Martha) said...

Sorry to hear about your troubles Mr. S. I've never had to deal with scale - yet - so I'm not sure what I'd do if I enountered them. I have dealt with mealybug (pure evil) and just tossed out the infected plants (not in the mood to fight these things). Anyhow, I hope your plants recover and your problems end there.

I also wanted to say that my mother has been growing her hibiscus for years the way WCW mentions. In the fall, she places her hibiscus in a cool, dimly-lit spot in the basement, lets the leaves fall, barely waters the plant and brings it back into bright light in March where it begins to grow like a weed. By May the darn thing is filled with leaves and flower buds. So yeah, that method can work like a charm if you have the patience for it.

Liza said...

Oh ew, spider mites gross me out. I'm sorry your hibiscus has them. And the scale, well, I think you know already how I feel about scale. It might as well be called dumpster bound.

Unknown said...

Here's to hoping that either doesn't develop into a collection-wide outbreak.

My condolences. :(

CelticRose said...

I've had scale once. Just one, on one leaf of a Kalanchoe marnieriana. I simply removed the leaf and flushed it down the toilet. I haven't seen anymore since. I must really stink to have them on a plant where you can't remove the infected leaves.

I had cyclamen mites once. They came with the cyclamen (I was a newbie and didn't know what to look for.) I disposed of the whole plant.

I had spider mites on my Dracaena marginata. I think they may have come with the plant (another newbie mistake). I wiped the leaves and misted it thoroughly with plain water, and I've been misting it daily with a more thorough misting every few days. It seems to be working -- I haven't seen them again. *crosses fingers* Of course, the plant is far enough from other plants that they can't spread. It must be a nightmare to get mites in your setup.

Karen715 said...

I'm sorry about your troubles. I just threw out a couple of Hedera because of mites--they reached a point where an attempt at control wouldn't be worth it.

For scale, I have had luck with imidicloprid, but only as a part of two pronged approach: In addition to adding the systemic to the soil, all visible scale must be removed by wiping the leaves with alcohol. I managed to rid my ZZ plant of scale three or four years ago this way. The alcohol cleansing alone won't work, and the imidacloprid alone takes too much time.

Anonymous said...

Oh loathsome pests. And for plants I hold especially dear I will try . . . and try . . . and suffer. I could never claim to have prevailed, just, maybe, to have controlled for a short time. And I live in fear of them spreading, which means that I usually finally compost the host plant. Glum.

Try using some of those bamboo skewers, the fine ones, and wrap some cotton on the end - makes a q-tip that reaches down in the spines and saves you some bloodletting.

Diane said...

I got scale once, on a sago palm, which was too pointy and complicated to work on so I pitched it. No other scale yet, knock on wood, and I seem to have licked my mealybug infestation (not literally). I'm trying the dormant Hibiscus thing this winter and the plant is mostly dormant though I noticed the other day that it's starting to form pathetic little flower buds, not at all what I'd intended. Maybe I gave it too much water? I think I'm going to cut it back soon and move it upstairs to bright light and revive it for the season. At least it's easily replaced if I screw up.

Joseph said...

My experience with systemic insecticides is that they are good at preventing infestation, not so good at curing an already existing one. Or, as someone else commented, good in combination with some other form of control to knock off the wee little ones you missed, and keep them from coming back.

watergal said...

The granules take time to get translocated throughout the plant. They work, but only in conjunction with repeatedly attacking the ones on the leaves. Rubbing alcohol for that works well, plus you can spray the leaves with an imidacloprid spray as well, but only outside, which is problematic for houseplants during the winter.

As for the hibiscus, I totally gave up trying to overwinter them indoors. It was spider mites one year, whiteflies the next, aphids the third, and then I was done.

I used to have a client with a cute little potbound hibiscus on her very sunny office windowsill. It had been there for years, bloomed its fool head off all winter, never saw a bug on it. I'd give it a radical pruning occasionally. I no longer go to that client, but I know her office got moved into the basement, and she was not optimistic about the hibiscus getting a suitable new spot in her house.

I'd like to try the overwintering a hib dormant approach, but I don't have a good spot to do so. Husband has pre-empted all the cool, dark spots.

cconz said...

I've had alot of problems with scale and always end up throwing out the plant. I have used the oil spray and it worked for awhile but they always came back. I have a prize Hoya that had a few and i deceided to use the systemic method and i haven't seem them again, 2 years running.

Anonymous said...

You have my sympathy in this difficult time. I was forced to sacrifice a really nice Pavonia to scale; fortunately it was in the kitchen window by itself and didn't spread.

I was once told of a treatment, never tried it myself: put the plant in a large plastic bag with a flea and tick strip for dogs, and leave it there for several weeks (sorry, the mind refuses to provide the exact timeframe.) This was back in the late '70s - we were still rather clueless about scary chems back then, so I don't know if what's available now might be potent enough - kind of hope not - maybe try 2, 3(?) I imagine if you found a clear plastic tub large enough you could use that instead of a bag for the Neoregelia and tape it to seal. I'd be curious to learn of anyone's experience if they try this.

And BTW, that mite pic is an excellent illustration of "INFESTATION". I can almost see them crawling.

Anonymous said...

Oh no!!! I feel your pain. I'm currently dealing with a super huge scale infestation in almost all the Kentias at work (a problem I inherited). Mealy bugs are floating around too :(

Aaerelon said...

Arghhhh! I hate pests. Good luck in your elimination endeavors.

Pat said...

Dear mr_, I, too, have had great success overwintering a huge (double-flowered, sigh) hibiscus in front of a small south basement window for years. Every leaf falls off, if a bud appears I remove it to preserve energy. For the spider mites that regularly infested it, I successfully use Murphy's Oil Soap in the spray bottle. Murphy's is a natural soap, not a chemical detergent. Love it for plants.

Ivynettle said...

Seriously, what the heck is wrong right now? Snipped back my Abutilon this morning to keep it at a managable size until I can move it outside again, looked at one of the bare stems - scale! Right in the middle of the most crowded windowsill (and how did they even get there? This plant has never been in contact with any of the known scale "patients")

I'm becoming tempted to get a Hibiscus after all. But that's gotta wait until I move out of this hole and get a place where I can have a cool overwintering-spot.

Pat said...

ivy,I'm not sure tropical hibiscus needs to be especially cool in the winter. I've left it upstairs in an East window during winter and it still went dormant on its own, losing all leaves. Aside: one cannot stop watering it in winter, wherevee it is.

Melanie J Watts said...

Wow that is depressing. I have had similar bugs on my plants. I used paper towel soaked in rubbing alcohol. but it only deters them temporarily. They inhabit my Monstera deliciosa, It is huge so I'm reluctant to throw it out. I hope your hibiscus survive the rest of winter.

Kenneth Moore said...

Spider mites I can sort of handle--they don't outright kill any of my plants, but they never seem to go away, either, which annoys me.

Scale, however, freaks me out. I haven't encountered it yet, so I'm scared that my first time will be one of those too-late instances. I keep trying to get my friend who works at the National Arboretum over to look at my plants (like an annual check-up at the doctor's), but he hasn't swung by yet. :P

mr_subjunctive said...


I know the smart thing to do is to get rid of the plant with the scale, but it's such a cool plant, I just can't bear to. I'll be watching it, and if it really seems to be an intractable problem, then I'll pitch it, but for now I'm hopeful. I'll be starting on the alcohol very soon (haven't been able to so far).

The mites are less of an issue. First, the Hibiscus were already not the only plants that had them, so it's not exactly a new problem (though it's definitely a much bigger problem with the Hibiscus), and second, they're waaaaaaaay off by themselves, at least thirty feet from any other plants, back in the basement again. So they may not get better, but they probably won't make anything else worse.

Anonymous @ 10 Feb 2:16 PM:

I don't know what they used then, but the active ingredient in a lot of flea and tick collars now is actually also imidacloprid. I don't know if enclosing the plant with imidacloprid would help; I'm not sure it's very volatile. But it's an interesting idea, and I might do that anyway, just to add a physical barrier around the plant to keep the scale from moving anywhere else.

Nature Assassin said...

My condolences. Look at all these comments... there should be a support group forum for dealing with insect pests! I know I'd use it.

I know you're not supposed to use horticultural oils on bromeliads, but I went ahead and put neem on my Neo when I found mealies. So far it's worked well. At any rate, it beats trying to remove them by hand, just as you said.

The Plantman said...

Spidermites Remedy: The Silicon emulsion foliar shine used by the interiorscape business. The stuff works like a charm. Spray the underside of leaves and whole plant a few times, giving the plant a solid water spray in the sink prior to application. The stuff works like magic and it's NOT toxic. It also works on Scales but not quite as good as Neem (see my comment under the name "Mitch" in the next Post about Scales)...

mr_subjunctive said...

The Plantman:

I'm not familiar with any silicone-based leaf shiners, so I don't know if there are any around to be bought. Any brand names?

Plantman said...

This is one of my regional wholesale suppliers in Cincinnati, Ohio. I'm pretty sure they sell their Foliage Wonder on line, retail. The stuff rocks! Yes it can make your leaves shine as if they are fake for a week or two but it really works against spider mites and mealy bugs (better than Neem or anything else). It's also non toxic to you and I.
The only fine print is that it makes tile, wood and laminate floors REALLY slippery and it causes leaves to be more easily burned by direct rays of sun for time > 1-2 hours. Lastly, it’s not to be used on fuzzy leaves. But, when fighting infestation like spider mites it can be sprayed on the bottom of leaves. I have yet to see a case where it has hurt the plants ability to transpire. Maybe I wouldn’t spray at night or in the evening…

Chris said...

Oh my! I didn't even know there were creatures like that and that you have to go to the lengths of wiping them with a tissue or spraying with oil. I thought a good ol' soap and water spray would be good enough for pests.

mr_subjunctive said...


Soapy water is pretty close to all you need for spider mites; the trick is in getting it on the plant to begin with. Sometimes you can fill the kitchen sink with soapy water and swish the plant upside down in the sink, sometimes you can spray soap on and then rinse the plant off again in the shower, sometimes you have to get a bunch of paper towels and hand-wash each leaf. I've done all of these, the last two very recently.

Before it got too cold to take plants outside to water, I was spraying them from all angles with a garden hose, which didn't eliminate pests altogether but did keep their numbers more or less manageable. Since that became impossible, though, I'm left with either hand-washing or trying to spray plants off in the kitchen sink, which doesn't work nearly as well. I'm in the process -- the long, agonizing, loud, smelly, dusty process -- of getting a shower put in the plant room, which will hopefully improve the pest situation and make watering go faster. Hopefully.

Anonymous said...

Hello from Seattle!

For scale, I use a 409 type spray cleaner on sturdier plants. I have also have used some other general alcohol-based spray house cleaner brands, but check them as some can be too strong. 409 has great alcohol and detergent agents to dissolve the little domes. I have a 50 year old Christmas cactus that got scale mysteriously, some orchids etc. Works like a charm.

Take outside or to a well ventilated room and clean it. Spray to wet and rub the leaves gently to get 409 into every nook and cranny and scrub off all those scales. Let sit to dry. Inspect, did you miss any? It will be very smelly as you have just gotten every surface wet with it. There will be some on the soil too but don't drench the soil with it. Water if you got too much on the soil. (Leave outside in nice weather if it is too much "clean" to bear, or lock in its own room IF it bothers you.) Repeat to break the bug maturity cycle. I use 7 to 14 days as a guide to most plant infesters. Twice washed is usually enough The citrus tree on the balcony will spontaneously get them and it gets a bath once or twice each year. You may loose a few leaves, but the plants are not worse for the wear. If the plant can be handled and is tuff in any way you can use this method. Rinse the leaves after it sits a while on more tender stock and orchid crowns. Systemic can be added as well but takes quite a while to soak into the cells but is good insurance. I think the detergent left on the leaves may just dry out the baby bugs. The bugs can come in on purchased citrus fruits, on clothing, and other stealthy ways.
Mealy bugs can decimate an African violet collection, quiet, pernicious, and invincible, until you use Marathon systemic, that is. I mix it in with my potting mix as I pot up new plants, scratch it into soil add water activate it for pots as they come in the house, even when I put down leaves. Every time I do anything with the soil for any gesneriad, Marathon is there. No problem, no soil or foliar mealies, no more. Happy-ness. Rohm

Chris learns about plants taking a shower said...

That's amazing. I've never heard of submerging plants in soapy water. My mind is tingling with possibilities again.

Can I ask for a couple more tips?

If I spray soap & water, how long before I need to wash it off. Right now, I just spray. I don't even wash it off. I just figured it will be washed off naturally the next time the plant gets watered.

My petunias were recently attacked by so many ants, but they were in the soil. Should I spray the soil? I just ended up drowning the plant for about half an hour to kill critters in the soil. It may have worked, but my plant still looks a little anemic.

mr_subjunctive said...


Well, you don't have to wash the soap off the leaves at all, necessarily, but I usually do, immediately after putting it on.

I really don't know what to do about ants, but anemic-looking Petunias are a problem we had to deal with at work a lot. I recommend asking at your local nursery for iron supplements. Both Petunia and Calibrichoa seem to have a very high need for iron.

Chris is nursing his Petunia said...

Hey thanks for the tip. You know what I did? I sprayed my petunias with soap solution every two days. I also moved around the pot to maximize sunlight. I suspect some of the rotting may be due to over watering too. Before getting iron supplements, I'm also interested in finding out organic sources for those. Any suggestions? I put in egg shells for calcium although I really saw that tip for tomatoes. Figured it might work for petunias too.

mr_subjunctive said...

I don't really know of any organic iron sources, never having looked. I'm also not sure what would even qualify as an organic iron source in the first place.

Chris said...

I got a little curious too. Apparently, iron deficiency can be cured by correcting soil PH since alkaline soil tends to tie up iron. Adding coffee grounds (acidic) might do the trick. You think?

mr_subjunctive said...

Coffee grounds might work, but the soil may or may not have iron in it to begin with. If there's no iron in the soil, acidifying it isn't going to release anything.

And I have no idea how much iron is normally in potting mixes to begin with.

Also, coffee grounds are less of a good idea for container-grown plants, because they break down into smaller particles much faster than bark, peat, perlite, and other common components of potting mixes. I think they can still be used (and have added very tiny amounts of coffee grounds to a containerized plant myself, with my Murraya paniculata: I'm uncertain about whether it was particularly useful, but it doesn't appear to have harmed the plant any), but don't add very much, lest you turn the soil into something that will compact around the roots.

Chris said...

If not for nutrients, it's still cool to use coffee grounds because it makes the garden smell better. ;-)