Pecan shells harden in late August. Water deficiency in August, before the shell hardens, causes the trees to drop of most of the crop as described in the first question. This drop follows a good rain or irrigation following the dry period, especially in sandy soil. Since it follows a rain, drought often doesn't seem to be the cause. An early freeze will do the same, but the pecans will be well filled.
Pops are stick tights with no meat inside.
He also thinks that a characteristic of pecans, alternate bearing, is also involved. Some pecan varieties, like many other fruit crops tend to produce heavy crops one year followed the next year by light crops. According to Dr. Herrera, established pecan trees need 150 to 200 gallons of water on the hottest day of the summer. In very dry weather, especially in a lawn setting in which there are not many trees around to break the wind, it is difficult to provide sufficient water to the trees. He also observed that few pecan trees in a lawn are provided that much water in the first place.