A recent Pioneer Hi-Bred newsletter recently addressed how hot, dry weather impacts corn yields. As every farmer knows, leaf rolling is the first sign of plant moisture stress. And eastern corn growers have seen more than enough of it already this summer.

Here are a few pointers from that newsletter and ag college sources that may help assess yield damage, or possibly prevent it.

Some hybrids may leaf roll quicker than others. But if it happens for only a few hours in the heat of the day, it's likely to have little impact early in the season.

When it starts early in the morning or if plants fail to unroll at night, that's a clue of much more severe stress. One of the more common irrigation mistakes is not watering during the V6 to V8 stage – about three weeks after emergence.

Water uptake at the V10 stage (10 fully developed leaves or 10 leaf collars) is less important than at V6 to V8.

Moisture demand kicks up again during the two-week period before and after pollination. Leaf rolling is severe enough to impact yield. That's roughly the V12 to V14 growth stage when kernel rows around the ears are being determined.

Ear size is determined between growth stages V14 to V17. If water is inadequate at this time, a small ear size may be set.