Christmas tree pests and weeds required restrictions and requirements to be placed upon Christmas tree growers with plantations in "gypsy moth regulated areas". The restrictions and requirements included ongoing site monitoring, active moth eradication by the grower, accurate record keeping, and government directed moth eradication programs. Failure to abide by the rules could result in revocation of the "approved grower" status from the Canadian Food Inspection Agency. The major types of conifers cultivated, pines, Douglas-firs, true firs, and spruce trees, are all affected by some types of insect pests. Douglas-firs are most vulnerable to the Cooley spruce gall adelgid. The true firs are most susceptible
Tree of virtues and tree of vices (c. 1310-1340). The nodes of the tree-diagrams are the Cardinal Virtues and the Cardinal Vices, respectively, each with a number of secondary virtues or secondary vices shown as leaves of the respective nodes. While on a tree of virtues, the leaves point upward toward heaven, on a tree of vices the leaves point downward toward hell. At the root of the trees, the virtues of "humilitas" "humility" and the vice of "superbia" "pride" is shown as the origin of all other virtues and vices, respectively. By this time, the concept of showing hierarchical concepts of medieval philosophy in diagrams also