Question
I was asked to look at a Leyland Cyprus in the Washington DC area. It was a replacement Cyprus and is aprox 20 feet high and was acquires 12 months ago. The top 5 feet of the tree has now died. It is on a friend's property so I don't know how long it took to die off of whether is moved down the tree slowly. It is in a garden bed on a slight sloping area. Any suggestions would be grateful to rescue the Cyprus.

Answer
Since you said that the top was dead I would think this is an insect called a weevil. It attacks the trunk and bores into the wood killing the area above the attack. There should be a slight swelling or maybe sap flowing from the trunk where the dead area and the live area meet. There are also a couple of foliage diseases that will cause Leyland Cypress to dieback, these usually show up as individual limbs dying either on the sides or the top.

With just the top dying the weevil is the best answer. These can be controlled by cutting the dead top at the living part and spraying the trunk with an insecticide called Onyx. Check with your local nursery fro Onyx. The spray will protect the tree through the growing season from additional attacks. Over time one of the side limbs near the top will take over as the new top but you will have a slight crook in the trunk. this will take several years for the limb to grow as the top leader.