My co - worker is trying to save some very old Jeffrey Pines (6,000 Ft elevation) at his house.

They are being killed by Bark Beetle infestation.

Any recommendations on how to treat this? According to him the trees have not been getting enough water which has caused the sap production in them to decrease and the sap is what deters the beetles. Outside of watering them more, are there any other steps he can take that?

Any and all suggestions welcome. 

Best,

Beth McClung