The first sign of attack are holes penetrating tree bark that are surrounded by sawdust. The are referred to as “pitch tubes” and remain visible for days after the initial attack. Eventually blue colored sap begins to appear on the outside of the tree after the beetles have completed their takeover. About a year after the attack the pine needles of the tree turn red, orange, and yellow which is why beetle kill forests have a red hue from a distance. After two to four years of infestation the trees turn grey and the final death process sets in.