This is the first year I have seen them, I only know what little I have read online but 2013 was the first year they were found in texas and have gotten worse. Basically they are eating on the plant and what they leave behind stops the plant from breathing and turns it brown. There are a few good articles the schools have put out to be found online by searching Sugar Aphid.Not familiar with this pest....tell us what you know.
It's my understanding that Alfalfa can't be successfully seeded in an existing stand of Alfalfa.Maybe we will have enough viable alfalfa seed to establish a volunteer stand in the old stand. I hope the stand I plant in less than a month is not my last alfalfa planted.