Imidacloprid rules Kills everything except caterpillars and red spider mites. For that I simply use warm water and submerge the entire plant. Biological systemics are bad. Its good that they help our enviroment but its bad that they simply have no effect on the things you want to kill. I used bayer advanced and I get brown spots and yellow growth with my cacti. If cacti don't like the stuff then no plant will
I use it. I've used it on potted plants like hoyas and palms with very good results. I mix 2 tablespoons in a gallon and use it to water with.
I have never used it on bareroot or mounted orchids.
I have used the already premixed Bayer spray on orchids for mealybug, works great for fast kill, but Neem Oil works just as well, mixing 1 Tbsp in a gallon and spraying the plant with a hand sprayer
I used the label directions which is 2 ounces per quart =8 ounces per gallon. I don't think the insecticide did the damage. I think it was the fertilizer contained in the 3 in 1 Bayer.
Even using it at that strength, I do have some mealies left in a large pot or two. I'm sure retreating those pots would get rid of the bugs but I'm a little gun-shy now.
I'm in the process of unpotting, checking for dead/damaged roots and potting into fresh mix. Luckily most plants have new growth and roots starting.