From UGA Chatham County Extension Agent David Linville:
We are in a serious drought. I have not had a drop of rain at my house in 6 weeks. I know some places got an inch or 2 a few days ago. I am getting phone calls about the leaves of trees and shrubs yellowing up and then dropping. This is a survival mechanism of the plants when they are without water. If this drought continues, I am afraid we are going to see a lot of dead trees and ornamentals next spring. Weakened trees and shrubs are also susceptible to beetle and bore damage. The plants no longer have the strength to protect themselves.
Tip #1. DO NOT FERTILIZE! Many people then put down fertilizer to help the plant and this is absolutely the wrong procedure. Fertilizer forces plants to grow which means the plant needs even more water.
Tip #2. I do not have an irrigation system but I am strongly suggesting you water your trees. Hook up the water sprinkler to your garden hose. I place the garden hose about 15 feet (give or take some) away from the tree and I let it water for 4 hours in a complete circle. You need to do a deep watering. This is not the time to be worried about your water bill. Taking down a dead tree can cost way over one thousand dollars. You want to put out more than one inch of water. Remember a 100 foot tall tree will send out roots 4-5 hundred feet from the trunk. A mature oak tree will use more than a thousand gallons of water on a hot day. Water your trees right or don’t water at all.
For more information from the UGA Extension Service, visit http://www.ugaextension.com/chatham/anr/CoastalHomeownerLandscapeTurfMonthlyUpdate.html
For more information on outdoor watering, visit http://www.gaepd.org/Documents/outdoorwatr.html
More watering tips from Friend of Trees in Portland, OR