Ambrosia: A plant genus of the family ASTERACEAE. The POLLEN is one cause of HAYFEVER.Artemisia: A plant genus of the family ASTERACEAE with strong-smelling foliage. It is a source of SANTONIN and other cytotoxic TERPENES.Ophiostomatales: An order of fungi in the phylum ASCOMYCOTA that are important plant pathogens.Rhinitis, Allergic, Seasonal: Allergic rhinitis that occurs at the same time every year. It is characterized by acute CONJUNCTIVITIS with lacrimation and ITCHING, and regarded as an allergic condition triggered by specific ALLERGENS.Pollen: The fertilizing element of plants that contains the male GAMETOPHYTES.Beetles: INSECTS of the order Coleoptera, containing over 350,000 species in 150 families. They possess hard bodies and their mouthparts are adapted for chewing.Meteorological Concepts: The atmospheric properties, characteristics and other atmospheric phenomena especially pertaining to WEATHER or CLIMATE.Air Movements: The motion of air currents.Xylariales: An order of ascomycetous FUNGI which includes many economically important plant parasites as well as saprophytes.Croatia: Created 7 April 1992 as a result of the division of Yugoslavia.Allergens: Antigen-type substances that produce immediate hypersensitivity (HYPERSENSITIVITY, IMMEDIATE).