Norway spruce trees produce a mixture of substances as protection against insects and fungal infestation https://www.ice.mpg.de/496050/PR_Zaman
Norway spruce trees produce various monoterpenes to protect against insects and fungal infestation. Mixtures of monoterpenes have been shown to be more effective than single monoterpenes against bark beetles and two of the three fungi tested. The study is the first to show both the synergistic effects of a variety of substances and the use of different defenses against different enemies as an explanation for why trees use mixtures of defenses rather than single substances for defense.
— typical components of resin — to combat bark beetles and the fungi associated with