Fast-growing corn in the last week has resulted in a few scattered plants in some fields - at least in central and west-central Iowa - displaying bright yellow leaves waving above the canopy (see photo). Corn with these symptoms is around the V5 to V8 growth stage. The yellow upper corn leaves are sun-starved, entrapped earlier in the whorl by more mature leaves. They will wave for a day or more above rapidly growing crop canopies before turning green.