Originally Posted by harveyc
I'm not sure if you have a local source for commercial products such as Surround or PurShade, but I think you can probably make a suitable homemade spray from using gypsum and adding enough water to make a spray with viscosity similar to paint diluted with 50% water.
You could have Surround shipped, but I don't know if it would be worth it when you factor in the cost of shipping:
Surround® WP (OG) - 25 Lb. - Johnny's Selected Seeds