Question
Sudden dead leaves on  forsythia.  Planted in shade.  Very frequent watering due to new sod.  All of the leaves on two or three stems are dead.  The stems are dead with holes at the tips.  Seems it has been very quick and sudden.  Has jumped to one stem of a second bush.  The leaves do not appear to be attacked.  Could Roundup weed killer have traveled 7 or 8 feet to get into plants?  The roundup would have to go uphill.  Plants were put in one year ago.  We are in Georgia and are in a year long drought but I don't think that is it as we irrigate.

Answer
Roundup can move anywhere from anywhere.  The key to roundup is that you would see a yellowing in the terminal of the plant most likely without leaf death.  The plant may be experiencing transplant shock even a year after being put into the ground.  Cut any dead branches off and then sit back and see what happens into next spring.  It is not likely that there is a root rot in a drought year.  Forsythias are normally very resistant to diseases and insect pests.  I would do nothing except watch the plant over the next few months.  I think it will be OK.  Good Luck.