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I regretfully come posting asking for advice on how to get rid of a very tenacious spider mite infestation in one room of my indoor plants. I have become convinced these pests have become pesticide resistant because they have shrugged off neem oil, tobacco water, Sevin (Carbaryl), Malathion (a very strong organophosphate pesticide), Doktor Doom (pyrethrin, both the fogger and the spray), and something that came highly recommended called Wipeout.

Each attempt was whole-hearted, with me applying the pesticide at least 4 times liberally on the undersides of the leaves, spaced 3 days apart to get rid of the newly hatched eggs. Each time I see improvement for about a week before the leaves start getting sucked dry at an even more accelerated rate. I have also tried dusting with diatomaceous earth, and wiping down the affected leaves, all to no avail.

I am certain it is spider mites and not some nutritional deficiency because their webs are noticeable, I can see the wretched creatures when I inspect the leaves with a high powered magnifying glass, and its affecting multiple species of plant. Unfortunately heavy spraying with water is a non-viable option as the plants (mainly plumeria species) will suffer root rot if given too much water. I really do not want to have to discard these plants because they are fairly mature and rather unique varieties.

Is there anything on earth that will kill these vile pests without destroying my plumerias? As you can see I am willing to use just about any chemical at this point, but I am open to just about any suggestion. Your help is much appreciated.

[UPDATE] I tried both of Shule's suggestions of wiping down the leaves with rubbing alcohol and I spent some money on the predatory mites recommended. Rubbing alcohol didn't seem to damage the leaves terribly, and was very effective on the large broad leaves of the plumeria where it was fairly easy to wipe evenly. None of the leaves I wiped down suffered any additional damage. It was less effective on my ornamental peas where the small leaves made it difficult and tedious to wipe all the leaves. So I spent $60 on some Phytoseiulus persimilis mites. I hope they become established and permanently rid my plants of the irritating spider mites. I guess the moral of the story is don't use pesticides against spider mites. Thank you everyone for helping save my plants.

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    I think the problem is in other places. Before using again pesticide, check where the spiders lives, why you have so much spiders returning. I think you should check the real sources of spiders, and you should start there to block them. No cures will help you, if new (untreated) spiders arrives. – Giacomo Catenazzi Sep 7 '16 at 8:36
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    A picture would help and a description of what possible avenues of entry for new spider mites exist: for example, are there open unscreened windows? A vent that draws air in? Is it hot and dry in the room? – kevinsky Sep 7 '16 at 10:10
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Predatory mites that eat spider mites might help. You can buy them, but they may be expensive. Make sure to remove any substances left on the plants that might kill the predatory mites.

We have a similar problem. This may not be an option for you, but I decided just not to start my garden plants indoors because of the spider mites. They didn't seem to be a problem started in the unheated greenhouse while they were there, except on a few ground cherries that I left in there too long.

I think all our apple trees and rose bushes attracted the spider mites, and they made their way indoors somehow. I think they'll be less of a problem if we remove the trees.

I haven't found anything that I've actually used that gets rid of spider mites. I haven't tried predatory mites, though.

I've heard that rubbing alcohol might be effective (I'm not sure about the eggs). I'm not sure if that would damage your plants. I haven't tried it. This makes me wonder if anti-lice shampoo would work, and if it would be safe. Probably not.

I think the spider mites hang out in the soil, too (not just on the leaves and stems). I've seen webs going to and from the soil (so that's my rationale). They also seem to hang out on plants they don't damage (so they can help to reinfect other plants). So, if you missed them in the soil or neighboring healthy plants when you tried neem oil, maybe try it again, covering the soil and the plant, and all the other plants. Neem oil is supposed to stop them from knowing they need to eat, drink and breed. I don't know that it kills them outright. Maybe a combination of that with a miticide at the same time would help.

Predatory mites sounds potentially a lot easier than other options, though. I'm guessing they may need a water source like ladybugs do to keep them alive.

Ladybugs don't seem to eliminate spider mites, by the way (even indoors; yes, we had some indoors once, with infected plants--not loads of them, though).

Sorry I wasn't more help. I'm interested in the answers you get, too.

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    I tried wiping down a few leaves with rubbing alcohol today. We'll see what happens... I figure at the very least it will remove some of the pesticides in case I need to shell out for the predatory mites. Thanks for the tip! – mattb Sep 8 '16 at 3:14
  • I've heard the alcohol story a few times. My question is - is it the alcohol that kills the mites or is it the wiping that removes them? Would spraying my plants with alcohol work or would wiping my plants with water work? Or is it both the alcohol and the wiping together? Is there any information on why alcohol seems to be effective? FYI, I tried alcohol on my plumeria once, and it seemed to reduce the infestation temporarily, but the mites came back within a week. I'm guessing I just wiped off a bunch of mites but didn't kill any or their eggs. – Thomas Nov 7 '17 at 23:02
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Spider mites like warm, dry conditions and will thrive in such an environment, so it sounds as if that's what you've provided them with. Plumeria species like to be kept evenly moist from spring through summer, with significantly reduced watering in winter when they're dormant. They also like moderate air humidity - humidity and a plant that's well watered means spider mites don't like the conditions so much. You've mentioned Plumeria, but haven't said what your other plants are, so as far as the Plumeria are concerned, you could use pebble trays half filled with water to stand the plants on to increase humidity around them. More info here

http://www.guide-to-houseplants.com/plumeria-care.html

As for chemical treatments, the latest recommendation is to use a specific miticide spray rather than general insecticides, so you could try that. There's one on Amazon in the States called Mantis, but I can't speak for its efficacy. You might be interested to read the link below - it speaks of spider mite outdoors, but says there is evidence to suggest that some insecticides actually increase spider mite population, although quite why is anybody's guess, other than the assumption that insecticides are indiscriminate and kill other insects which may prey on the mites. Sevin, pyrethroids and some organo phosphates are mentioned as having this effect, so you might have been unwittingly exacerbating the problem.

http://columbustelegram.com/news/local/use-caution-with-insecticides-to-control-spider-mites/article_b6213642-a087-5be6-9b3f-96def4881f42.html

  • Good to know about the pesticides, I'll stop those immediately. The plants that are being destroyed besides my plumerias are my mint (which I am probably going to toss since its been sprayed with too many pesticides to be even close to edible, and is easily replaceable), and mimosa pudica aka the sensitive plant (less easily replaceable). – mattb Sep 8 '16 at 3:11
  • Just FYI, the spider mites in my house seem to stay around when it's humid, too, although the kind of damage they cause seems, but probably isn't, different. Some plants tend to get edema very easily when it's humid and spider mites are around, like this: thehotpepper.com/topic/21141-diagnosis – Shule Sep 8 '16 at 4:50
  • @Shule - sounds like more than one type of pest; your link speaks also of gall midge, that is, the bumps were assumed to be oedema, but were more likely some kind of midge rather than mite... and different plants suffer differently perhaps – Bamboo Sep 8 '16 at 10:05
  • @Bamboo I don't know what the link talked about. I was just showing a picture of what the edema looks like. I haven't learned about midges, yet. I'll have to look into that. – Shule Sep 8 '16 at 11:12
  • The bumps on my leaves didn't seem to be galls, but rather parts where spider mites had sucked a little fleck off, and the leaf reacted to the humidity, making it curl out, looking like a bump. It's hollow, though, and you can see the indent on the other side. The aforementioned flecks are there when it isn't humid. – Shule Sep 8 '16 at 11:16
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It makes me crazy to read that you may use pesticide inside... I re-read your question and saw it was a plant garden. Never mind. Be careful with pesticide.

One thing you could try is to use Diatomaceous Earth. This will arm any insect or arthropods because its so thin that it goes inside their joins and break them down.

Plus, it is not a chemical you can't use in organic gardens: its a natural occurring type of soil, with no known health impact.

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    I did try dusting the plants with some Diatomaceous Earth. It didn't seem to hurt or help... but perhaps my technique was lacking... I have read that spider mites primarily live on the underside of the leaves and I'm not sure the diatomaceous earth sticks underneath the leaves... I'm currently doing some more research into this option. Thanks for the suggestion! – mattb Sep 8 '16 at 3:07

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