I've always used
neem oil and
ProTekt to keep PM and spidermites at bay for years, and it's worked beautifully. Not only are you thickening cell walls with silica; but getting the obvious multi-purpose benefits of
neem oil.
I haven't had spidermites or PM issues for many years it seems...
Some people turn away from neem, I believe, because they aren't applying it most efficiently. I've said this a thousand times, but here goes again:
Mix
neem oil directly with silica at a 2:1 ratio. Strength of dose can be anywhere from 5ml to 30ml per gallon, though I've never really gone higher than 20ml as a high dose.
So for example, as a low maintenance dose, mix 10ml
neem oil with 5ml silica. This will turn to a light yellow, milky like substance.
Add this to a gallon TEPID or lukewarm water for best results. Mix well. Add surfactant;
yucca extract works great.
Right before lights out, turn off fans, spray underside of foliage, then spray upper side of foliage - plants will be drooping like they're thirsty if you've mixed and applied properly.
The next lights on "morning", the plants will usually be stoked, reaching for the light due to their affinity for the neem...