Avid or Imidacloprid (or both) for Thrips

There is really no need to alternate pesticides by application. A typical treatment should be to select an appropriate pesticide and use it three consecutive times at one-week intervals. That is done because most pesticides only kill adults, so the repeated treatments increase the probability that you will get the immature stages from earlier treatments as they mature.

The next time you need to treat, then you switch to a pesticide having a different mode of action (MOA) and use it for the same, three-application regimen.

In cases where I've mixed pesticides as Marni suggested, I still do the same 3-treatment cycle, then find one with a different MOA than those for the next go-round.

 

You may want to check out the resources on St. Augustin Orchid Society. i find this document particularly helpful: https://staugorchidsociety.org/PDF/PesticidesforOrchidPestsbySueBottom.pdf

Like Marni, I use both but I don't have much trouble with thrips.

 

Avid (or Abamectin) is a miteicide and is primarily used to control spider mites. It is ineffective at controlling most other types of insects pests (mealy bugs, aphids, thrips, white flies, ants). The imidacloperid is a general insecticide that is effective on most common insect pests, it is systemic and if you use it only as a soil drench it will take 14-21 days to be absorbed and translocated throughout the plant. Delaying results for a couple of weeks, making it seem ineffective. Using imicloperid with a contact insecticide, not Avid, will give quicker results. With thrips it well take a couple of rounds to get rid of them, especially if you have flower buds.