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Spider mite

Trouble shoot problems you are having with your cactus.

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Spider mite

Postby Isometric » Sun Oct 10, 2010 1:42 am

Hello everyone, I just want to confirm that this plant, P aselliformis, is infested with red spider mites. And that a correct method to get rid of them is to use malathion.

Are these correct?

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Postby Shmuel » Sun Oct 10, 2010 8:03 am

What great looking plants! Be careful of burning them with pesticide and if mites, they need repeat spray to break the egg adult cycle. Why not use a systemic?


I also have a hard time telling if damage is mites or not. I don't see any tell tale webbing, but I think there are other mites that do not make webs. I have been using alcohol and sulfur for mites, and I think I am successful - not sure though. I just made a mix of tobacco from 2 cigarettes in a cup of alcohol - going to try that.

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Postby hob » Sun Oct 10, 2010 9:48 am

Bayer Provado Ultimate Bug Killer Aerosol
is the only thing i can find in the UK to kill mites, not the same as the Provado Ultimate Bug Killer Concentrate which does not kill mites.

i don't know if it is available over there ??

http://www.grovesnurseries.co.uk/products/bayer+provado+ultimate+bug+killer+aerosol-7685.aspx
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Postby Isometric » Sun Oct 10, 2010 10:50 am

Any thoughts on using malathion. I've seen a post by iann saying that malathion would work. And that imidacloprid doesn't work, which is true I think, since I've used it a few times and the plant is still rusty red. That's why I want to know if it is actually infested with red spider mites.

When the mites die will the damaged part of the plant stay red or is it just the mites that are red?

Meanwhile I will try to find the Provado aerosol.
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Postby luddhus » Sun Oct 10, 2010 11:57 am

Isometric wrote:Any thoughts on using malathion.


It is classified as an acaricide, so it should work.


Isometric wrote:When the mites die will the damaged part of the plant stay red or is it just the mites that are red?


The damages are irreparable, so the plant will remain scarred.
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Postby iann » Sun Oct 10, 2010 6:13 pm

Confirm you have mites before spraying at all. The damage could be something else entirely. Or you may have had mites but now they're gone. Spider mites can be seen with the naked eye, pale beige dots and usually quite prolific by the time you notice damage, but easier to ID with a lens. Other mites may be smaller and almost impossible to see without a lens, but unmistakable with one.

Mites can be killed by all sorts of sprays although they can develop resistance very quickly so be prepared to try a different one. I don't know if you have systemic miticides available to you. Here we don't and it is necessary to spray several times a week or two apart to get good control of successive generations.

Any spray risks damaging the plant. Keep it out of the sun for a few days afterwards. Maybe just spray one and see if anything terrible happens. Often, existing damage will be further dessicated by the spray and suddenly appear much worse. The scarring won't every be cured, but on this plant it will disappear towards the base of the plant surprisingly quickly.
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Postby Isometric » Sun Oct 10, 2010 10:39 pm

Here's another picture from a different angle. I'm worried about the one on the far right, it already has very little green. The 'advanced corking' is definitely damage right? Whether due to spider mite or not. I haven't seen anything running around the plants while closely inspecting it for a few minutes.

Image

What if one were to completely submerge a plant in water for a few minutes? Will this suffocate animal organisms on the plant?
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Postby Shmuel » Mon Oct 11, 2010 7:41 am

Spraying keeps them down, but I don't think submerging in water will do much to kill them. Again, I am working on using alcohol spray and that seems to be doing something. My understanding is that the mites are really tiny and may be very hard to see. We used to shake a branch vigorously over white paper and watch for conifer mites moving - but I don't think that would work with cacti... Have you tied using a good hand lens to see them? Another possibility is to take as good a macro photo in as many megapixels as you can and see if you can zoom in on the picture to see them.

I assume you saw the article on mites at http://www.cactiguide.com/cactipests/#spidermite

Good luck!

Shmuel

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Postby Sutremaine » Mon Oct 11, 2010 7:17 pm

Shmuel wrote:Spraying keeps them down, but I don't think submerging in water will do much to kill them.

A good swishing in water treated with washing-up liquid or other surfactant would be sufficient to drive the water into any available spaces, wouldn't it? You'd need to repeat the treatment weekly for a while (probably. I don't know how developing insect larvae get their oxygen, so I can't say whether or not you can drown an egg), but let's see them develop immunity to that...
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Postby iann » Mon Oct 11, 2010 11:16 pm

Yes, dunking in water isn't really good enough, but an hour or two in soapy water is pretty effective. The problem is that you'd really need to do it several times a week or two apart and this isn't really practical. Still, if you are repotting then you can dunk it and at least knock back any pests.

The classic greenhouse mite doesn't like very high humidity and so spraying has been a traditional remedy. However, maintaining sufficient humidity to deter spider mites in a cactus greenhouse is almost impossible. In fact you probably do more harm than good. Extreme low humidity is harmful to all mites ad this is a more practical goal in summer at least. False spider mites, like the vast majority of mites, actually prefer high humidity so doubly useless to try and spray them into submission. They hide at the base of cacti and on the shady side to avoid being baked to death.

Two-spotted spider mites are certainly visible to the naked eye but you have to look closely. It helps to know what you're looking for and usually you will spot damage before the mites. False spider mites are smaller but brighter coloured, You can certainly see them with the naked eye, but really only if you have a big one and know exactly where to look. A lens is a much better idea. A good macro will show you mites quite well. I can get pictures with the standard macro mode on my standard digital camera but not really good enough for posting here. "Super macro" modes on newer cameras will show them quite well.
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Postby Isometric » Tue Oct 12, 2010 3:29 am

How does one achieve super low humidity? I've been saving hundreds of sachets of desiccants, what if I put my plant in an air tight container (possibly zip lock bags) along with a handful of desiccants? How long will I need to keep it in the bag to kill the mites?

First I'll try to get a magnifying glass. Is it possible to take a close up picture using the magnifying glass?
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Postby Shmuel » Tue Oct 12, 2010 12:50 pm

I wonder about using a hair dryer for reducing humidity on a cactus and killing mites?

I take back my suggestion of a hand lens if you have the kind of mites I have.

Last night I couldn't take it any longer and dug out my old dissecting microscope. 10x and 30x stereoscope. The first thing I saw under 30x was how amazing the spines and areoles were!!! I have some cacti that were suspected mite victims and I put them under the lens - and there they were. Zillions of them. And they are tiny. There was no webbing and these are definitely not red spider mites. Maybe some form of two-spotted mite, but very small. I took very primitive pictures with my cheapo Canon 540 camera and just held it to the eyepiece set on automatic. Not great pics, but I think instructive. I'll try for better.

I used Rebutia narvaesensis which is pretty small - about 1/2 inch diameter. Here it is with the microscope to get perspective. Note the tiny size of the spines.

Image

And here is the apex at 30x - the only part of the plant still green. Sorry for the focus, the mites are the small fuzzy things towards the bottom of the growing tip and just below it, not to be confused with the grains of sand.
Image


Here is another small cactus - not even sure what it is. The skin is completely white and not a web or mite to be seen with the naked eye. Note the size next to the pen point and especially the thickness of the radial spine.
Image

And here is the same at 30x magnification. The mites are on the spines and about as thick as the tiny spines.
Image
No wonder they could not be seen with the naked eye or even at 10x. A number of them are around the base of the spines and one is on the spine to the right. Another is on the end of a spine to the right and I saw this behavior very clearly - they would crawl to the of a spine and wave their legs as if looking for a ride. That is exactly what ticks do when they are looking for a host to latch on to. I suggest if one has a plant or so with mites that they wash hands well after handling the plants - otherwise they may an unwitting vector to spread to other plants.

I splashed the plant with alcohol and was happy to see lots of dead dessicated mites and only saw one that was still alive after the alcohol evaporated.(from the end of a spine where the alcohol did not reach). Still working on this and I have to get better pics...

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Postby iann » Tue Oct 12, 2010 8:06 pm

False spider mites, Brevipalpus sp. Some people claim they are B. russulus but no matter the name. They cause serious scarring for such tiny things.

Don't try to hurt them with humidity, they love it. Very low humidity will slow them down. Many insecticides, soaps, alcohols, etc. will kill them on contact but never seem to get them all. They breed quite slowly so spray 2-3 weeks apart.
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Postby Shmuel » Wed Oct 13, 2010 12:24 pm

Brilliant, Ian!!!

Yes, they are definitely Bevipalpus. I see also called flat mites and they are indeed flat. I am sure that is my prioblem and that could well be isometric's problem too. Too tiny to see and no webbing.

I am going for the alcohol treatment, perhaps with a soap also. I wonder if regular acaricides would get these?

I also saw (now that Ian pointed me in the right direction - I googled: Brevipalpus cactus) that the egg to adult cycle varies tremendously depending on temperature and humidity, roughly 1 - 3 weeks, but this is for a different species of false spider mite. Also they seem to mentioned more in Europe, Australia, etc than the US, but they are called a cactus pest.

Daiv, maybe these babies should be added to the cactus pest section... It would have helped me.

Good luck with these, isometric.
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Postby luddhus » Wed Oct 13, 2010 1:01 pm

Shmuel wrote:I wonder if regular acaricides would get these?


Yes, they do.
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