The rotation of chemicals applies only to those who disrupt physiological functions/pathways (I.e. Neuroinhibitors), such as imidacliprid (bayer/merit), Orthene, or Avid. It is impossible to develop resistance to soaps and oils because the only thing they do is clog their spiracles/nostrils.

Rotation needs to occur not across individual pesticides, but across families of pesticides. Each family of pesticides targets a different physiological function. One family will disrupt endocrine function (DDT, for example, what nearly wiped out the bald eagle), another might inhibit neurological function. There are a bunch of different families of pesticides that act in myriad different ways. So switching out DDT for another endocrine disruptor is not sufficient. Ideally you would rotate it with, say, a neurological inhibitor.

Intersperse freely with oil/soap of your choice.

I've seen this happen to an extent in my old job at a garden center in their tropical greenhouse. I would apply imidacloprid to everything with a non-mite pest. After about a year and a half mealy were not responding to the treatment and became a serious epidemic.

And just an FYI, there are differences in responses between mites/ non-mites and soap/oil. Mites respond best to oils, scales and mealy respond best to soaps.

This post was edited by terpguy on Fri, Nov 1, 13 at 17:59

Maybe a clearer way to state it would be rotate pesticides that act in a chemical manner, which usually interferes physiological functions.

The actions of oils and soaps are of a physical nature.

Super helpful. Thanks, terpguy! WC8

Thanks for posting this topic. And thanks to Terpguy for the thorough explaination. I have heard that soaps and oils do not lead to resistance but I was not sure of the why portion.

Terpguy. Thanks for the info. I have an ongoing battle with spider mites. A very nasty bug. I use bayer and avid. Avid seems to work the best. But I've noticed over the years that after a few applications of avid some plants start yellowing. So I need to know the next best on mites. I currently have the mites under control. But I know it is a matter of time they will be back. So I want to add another mite poison. Any suggestions? Thanks.

Greencurls, thats why. You will never adapt to someone holding your nose :)

Shavedmonky, do NOT use the bayer (I'm assuming the Rose and Flower Insect killer) for mites. The active ingredient - imidacloprid - does not affect them. Indeed, mites are different from all other insects because they aren't actual insects, they are arachnids. Try looking for something with either pyrethrins or permethrins in them. I just found a couple at home depot just yesterday with those (ortho brand, aerosol spray can). You can also look for kelthane or Tetrasan.

Interesting fact: some pesticides aimed at insects can actually cause spider mite explosions. Orthene is a huge culprit, I had this issue at my old job as well.

This post was edited by terpguy on Sun, Nov 3, 13 at 11:57

I think spider mite is more of a problem in closed culture situations. Never been a problem where I water with a hose because they seem to thrive in drier situations and the general advice is to water thoroughly and that means watering under leaves.
Sometimes you have bring out the big guns - imidacloprid is one, but perhaps the fear of a few bugs is overdone. If you use the big guns you wipe out the good guys. There must be some predators of red spider mite to keep them under control in nature.

Arthur, its not so much a closed system issue, all us window sill growers have battled mites. Its more of the following:

1) plant type - some are just spider mite magnets and will always have problems with mites no matter what you do, i.e. crotons and english ivy. I will never own either of these plants for this reason. No amount of spraying will abate the infestation.

2) environmental conditions - they thrive in dry environments, as you noted. THough this is slightly overblown. Here in the Washington D.C. area we have humid summers and they do very well here. and

3) Culture - related to #2, chronically running your plants too dry and letting them dehydrate - more than any other stressor - can net you a temporary mite infestation. Fixing your watering here will fix the mite problem. Happened on my Encyclia cochleata last winter.

This post was edited by terpguy on Sun, Nov 3, 13 at 12:31

Thanks terpguy. I will try either the kelthane or tetrasan. My orchids after a few applications of avid seamed to have a toxic affect on a few orchids. It causes premature yellowing. Do you have any experience like that with avid?

Truthfully I've never used avid myself. The only people I've known to use is are greenhouse production for other tropicals and annuals. Not on orchids

Terpguy says that for spider mites, "Try looking for something with either pyrethrins or permethrins in them."

One option I used for several years is 1600 X-clude, which is timed-release pyrethrins. The current product is 1600 X-clude Formula 2.

The manufacturer's site states it controls spider mites, as well as "Ants, Aphids, Beetles (Aster Beetles, Blister Beetles, Cigarette Beetles, Colorado Potato Beetles, Cucumber Beetles, Drugstore Beetles, Flea Beetles, Japanese Beetles, Rose Chafers, Trogoderma, Watermelon Beetles, Weevils), Caterpillars (Cabbage Worms, Rose Slugs, Hornworms), Centipedes, Cockroaches, Crickets, Flies, Fungus Gnats, Gnats, House Flies, Leafhoppers, Mealy Bugs, Moths, Rose Aphids, Scale, [Spider Mites,] Spiders, Stable Flies, Stink Bugs, Tarnished Plant Bugs, and Whiteflies."

Even if you hold the spray can upside down, it sprays full blast. Nice.

X-clude is "labeled for use in hobby greenhouses, homes, interiorscapes and landscapes on potted and flowering plants [including orchids], foliage, bedding plants, cut flowers, and ornamentals."

However, a commercial orchid grower who uses it says to take plants out of the house. Spray them twice, one week apart. We've got dogs and cats, and the orchids go outside to get sprayed.

The grower says to spray outside in the shade when there's no wind and to walk around the plants as you spray. I've taken plants to the patio on cookie trays and sprayed all of them at once.

When I've sprayed in the fall, there have been no spider mites over the winter. When I stopped, there were spider mites. Perhaps cause and effect - my humidity's low in the winter, and I tend to underwater.

WC8

Here is a link that might be useful: 1600 X-clude Formula 2