Garden Pests and Diseases: sticky substance on leaves, 1 by PudgyMudpies

PudgyMudpies wrote:
Hi all, I really need your help.
I noticed some yellow leaves on my Vigna Caracalla this morning and when I reached up to pull them off they were sticky on the back. I started examining the plant and there were ALOT of leaves like that. I immediately went into aphid/mite/whitefly mode and thoroughly checked all the sticky leaves with my magnifying glass under strong light. That has always worked for me, but there are no eggs, insects or webs on these and that is a first. With my magnifying glass and strong light I have always been able to spot the culprits! I went ahead and sprayed it with summer oil and added the rose systemic I use, but I sure would like to know what it could be!
In this picture you can see the light reflecting off the sticky substance and the color the leaves are turning. Does anyone recognize this?