The present invention relates to compositions comprising terpenes which are particularly suitable for treating plant infections, to methods of making such compositions, and to methods of using them. The present invention also relates to compositions comprising terpenes and hollow glucan particles or cell wall particles and methods for preparing such compositions; such compositions increase terpene stability and activity and provide a suitable carrier for the terpenes. The invention also relates to methods of using such compositions in the medical, veterinary and agricultural fields. In particular, the terpenes disclosed are thymol, eugenol, geraniol, citral and L-carvone.