Rose Rx is an organic solution for common pests, mites, and diseases.  Rose Rx 3 in 1 Ready to Spray contains Neem Oil which coats your plants leaf surfaces and protects them from insects and disease.  It will kill Japanese Beetles Organically and control blackspot, anthracnose, rust, scab, blights, and powdery mildew without chemicals. 

We've found that Rose Rx is an excellent organic fungicide for roses and a terrific product for killing and repelling Japanese Beetles without chemicals.  

From the Manufacturer:

Two way triple action: Insecticide – Miticide – Fungicide/Kills eggs, larvae and adults!
Prevents and controls blackspot, anthracnose, rust, scab, blights---stops powdery mildew in as little as 24 hours! Kills all life stages of aphids, mites, scale, whitefly, beetles, leafrollers---For use on roses and flowers as well as fruit, nuts, herbs, spices, houseplants, trees and shrubs. May be used indoors. Easy on beneficial insects. An excellent choice for organic and IPM gardens. Contains NEEM OIL organic insecticide. Approved for organic gardening.