What could be killing my rhubarb plants?

What exactly is going on with the plants,yellowing,holes in the leaves?

Gophers? Moles? Ground squirrels?

Hot weather, rhubarb is a cool season crop which dies back in summer months. The stalks will dry out inside, toughen, leaves will yellow and die back. This is natural. The best time to harvest stalks is springtime. If you desire it year round, pick in spring time and freeze for later use.

I have grown rhubarb for 40 years. If you are lucky, and weather conditions are favorable, sometimes it will grow back some in the fall. It is a perennial which will come back every spring.

Rhubarb loves organic matter. In fall when it dies back for winter, cover it with 3-5" of manure or compost. No worries, it will push up through it in the spring. It hates weed or grass competition, both will cause it to decline. Don't overpick it, remember leaves feed the roots.

Don't forget the leaves are poisonous due to oxalic acid which when swallowed crystallizes in your throat, pierceing the esophagus which causes swelling of ones throat, with the result, a closed airway restricting breathing.