The Genus Eucalyptus (Myrtaceae) consisting of over 700 tall evergreen trees is widely distributed and extensively planted for wood, pulp, medicines and aesthetic values. The foliage of the tree is rich in essential oils that are used extensively in perfumery, pharmaceuticals and food industries, and are held responsible for a wide spectrum of biological activity of the tree. Additionally, the terpenoid rich essential oil also plays a significant role in regulating floor vegetation under the trees due to its allelopathic properties. Of late, there have been attempts to utilize this property of the essential oils for the management of weeds, fungi, microbes and nematodes. The present paper attempts to discuss this broadspectrum potential of eucalyptus oil and constituent monoterpenes.