Beetle attacks certainly do affect plant water status — by both fungal disruption of xylem water flow, and loss of some water via resin solution exudation, which is obvious when you look at any tree under attack — unless that tree is so dehydrated already that it has so little water to exude. (realclimate.org)
In hardwoods, water moves throughout the tree in xylem cells called vessels, which are lined up end - to - end and have large openings in their ends. (scientificamerican.com)
These two features allow water to be pulled like a rubber band up small capillary tubes like xylem cells. (scientificamerican.com)