Maurice, I found this one which implies that where there was an enhanced effect it is not necessarily due to increased photosynthesis (e.g. one had increased nitrate assimilation). One cited article where they found an increase turned out to be because the strobilurin delayed leaf senescence of an annual crop, similar to what is mentioned in your article. The conclusion at the end of this specific article linked below was that the strobilurin did not increase yield over and above the effect of controlling disease. In another that I saw there was actually a reduction in
net photosynthesis
http://extension.agron.iastate...
Of course, none of these references is specifically about daylilies and daylily rust.
