Flat mites on the attack (Part 2)

[Steve Johnson]

Since I've educated myself on the ins and outs of flat mites, I'm taking a closer look at the little orange patches that were left behind on my Sulcorebutia rauschii:



I'm not sure how much of it is accounted for by mite damage as opposed to eggs being deposited, but the circled area sure looks like an egg sac. We'll zoom in on that spot:



So there we have untold generations of flat mites yet to be born. As I said in my first flat mite thread a couple weeks ago, I'm in it for the long haul, and tonight will be another session of my bi-weekly IPA spraying. Now, I know this is may be an incredibly silly question, but I have to ask anyway...

Pest mites can develop resistance to miticides, but what about alcohol? Logic indicates that they'll drink themselves to death every time you give it to them. However, I'm paranoid enough to wonder if persistent application of alcohol could end up with resistant mites that get nothing more than a tiny hangover before they sleep it off and go back to work. I'm not worried about this yet, but it would be helpful to get an answer here.

Thanks!

[hoteidoc]

Steve - thru-out my career in science, microbiology, veterinary medicine, I've never heard/read @ any resistance to alcohol (except alcoholics & that's a whole different phenomena!) - @ say 50% or better. Fruit flies & their larvae can actually be attracted to low levels of different alcohols, say in the 4 - 8% range (hmmm, sounds familiar!) The action of alcohol - on small organisms - is desiccation of cell membranes! So unless you have something with a exoskeleton of, say, a scorpion, it's going to have that dehydrating effect. So with small creatures, like mites or mealies, it'll kill them. The low level detergent that's frequenlyt suggested is to further disrupt cell membranes to carry alcohol into the cells better.

[Steve Johnson]

Steve - thru-out my career in science, microbiology, veterinary medicine, I've never heard/read @ any resistance to alcohol (except alcoholics & that's a whole different phenomena!) - @ say 50% or better. Fruit flies & their larvae can actually be attracted to low levels of different alcohols, say in the 4 - 8% range (hmmm, sounds familiar!) The action of alcohol - on small organisms - is desiccation of cell membranes! So unless you have something with a exoskeleton of, say, a scorpion, it's going to have that dehydrating effect. So with small creatures, like mites or mealies, it'll kill them. The low level detergent that's frequenlyt suggested is to further disrupt cell membranes to carry alcohol into the cells better.

Ah, excellent! Thanks so much, and I appreciate the fact that I passed the logic test here. Now just a follow-up thought...

Flat mites seem to prefer going after cacti in a weakened condition. After observing my first run-in with them in June, Ian pointed out recently-repotted plants as a good example. Since I have a bunch I got in July and again in the October-December period, I'm spraying vulnerable species with IPA as a preventative every 2 weeks until they're back in growth. While I won't let up on periodic inspections with my 10X magnifier, I'm not sure if regular prevention will be needed when I feel confident about demonstrating well-established, healthy growth in my 2013 acquisitions. As to the Sulco rauschii, it got amazingly healthy over last year's growing season thanks to the major improvements I've made in my cultivation practice. I'd say that winter dormancy characterizes cacti in a weakened state, so if I'm correct, even the healthiest plants can be vulnerable to flat mite attacks if the conditions in winter are warm enough. Well, like my L.A. winter these days. Under that assumption (hopefully valid!), well-established cacti that stay nice and healthy are much less likely to be bothered by them in the growing season. Such being the case, winter will be the time for bi-weekly prevention with IPA regardless.

There certainly aren't any 100% guarantees about catching flat mites in the act before they start doing any significant damage. However, I'm a lot smarter than they are, so if I keep up on the vigilance, I won't let them get the better of me or my cacti.

[iann]

I see no eggs (said Horatio). The eggs are large, oval, shiny, and orange, very noticeable in any lens that will show the mites themselves.

[Steve Johnson]

I see no eggs (said Horatio). The eggs are large, oval, shiny, and orange, very noticeable in any lens that will show the mites themselves.

Just came back in from another close-up inspection, and you're right -- no eggs. (No ham either, but that's a different problem. ) Okay, so the orange patches are due entirely to mite damage. I'm not sure if it applies to any other species that get attacked by them, but the rauschii has been pretty amazing at healing the skin after previous flat mite attacks. If the plant's recuperative powers continue, it's possible that the damage we're seeing now will be gone over the summer. Keeping up with the regular IPA spray should help.

Thanks, Ian!