Very!
Its pricey but works effectively.
And does amazing job on most mites including hemp russet mites.
I have used it in my outdoors for mites. And for PM and bud rot in late finishers.
Make sure you apply enough material, that is the appropriate volume of mix. Its organic. A light dusting wont do it. Most organic controls work best with larger volumes of materials applied than say a systemic chemical control like avid that doesn't need to saturate the plant.