I work for the ATTRA project and have a client in Pennsylvania growing organic Timothy grass for the horse hay market. He is preparing for the likelyhood of an infestation of cereal rust mite in his grass this summer. We have narrowed down the likely treatments as rotenone, sulfur and insecticidal soap.

I was wondering about rates, and timing of application (growth stage of the grass) for sulfur and soap. The sulfur could be applied at 200 pounds per acre as a powder, which is a likely practice he would be doing to supply sulfur as a fertilizer. This would most likely be done in the spring with our without mites present. Could he wait for the mites to put out his sulfor fertilizer and would that take out the mites, or should he use a liquid formulation of sulfur? If so, at what rate of liquid and when (after hay cut, 6 inches, 12 inches, just prir to hay cut)?

What is the most organically friendly way to get rid of spider mites in a grow room without using harsh chemicals?