In spite of recent rains, Cobb County is still experiencing Extreme Drought conditions, as shown on the U.S. Drought Monitor website of the National Drought Mitigation Center. Conditions have been dry enough for long enough that many trees that have not been watered adequately are showing signs of drought stress.
Different plants will show the stress differently, but in general, leaves may curl, wilt, turn yellow or brown, or drop off completely. Maple trees, for example, tend to lose leaves from the ends of their furthest twigs, almost giving them the look of having just had a burr haircut. Since symptoms of drought stress can resemble damage caused by diseases and insects, calling the Extension Office to check for other possible causes of problems is a good idea.
Instructions for providing adequate water to trees are included in the section on irrigation in the UGA Cooperative Extension publication "Shade and Street Tree Care”:
"Apply water to mature trees after two to four weeks without normal rainfall. Water deeply and infrequently to recharge the root zone. Check the depth of water penetration by pushing a thin steel rod into the soil. The probe will push easily through wet soil but with difficulty through dry soil. Probe the soil two to three days after watering to determine depth of penetration, and make sure the water is reaching a depth of 12 to 18 inches. Allow the tree to absorb the water before the next irrigation."