JKM - I think barley straw could be beneficial in your ability to control the golden alga (Prymnesium parvum) in your pond. I say this because P.parvum is a form of Chrysophyta algae and has recently been taxonomically placed in the algal Class of Haptophyceae. These algae are all planktonic, flagellated, delicate and very small compared to most other algae. My limited experience with haptophytes is that they are quite sensitive to copper as a herbicide. Since P.parvum is structurally a delicate individual, I think P.parvum could be pretty vulnerable to the derivatives from the lignin leacheates in barley straw. Keep us posted on the success of your efforts.
