Ozone: yellow, dark reddish mottling or bronze colored discoloration of the upper side of the leaf, interveinal; lower leaf surface without symptoms; more intense on older than on young leaves.
sulphur dioxide: yellow discoloration of the current years needles, extending from the needle tips; yellowish leaf discoloration, extending from the central part of the leaf, interveinal.
Fluor hydrogen: on conifers resembling damage by sulphur dioxide; on braodleaved trees discoloration extending from the rim of the leaf or spots between the veins. Chloric hydrogen: yellowing or reddening of the leaf rim, shoot dieback and death of plants; the symptoms can be mistaken for nutrient deficiencies, drought damage or fungal diseases.
Affected tree species
Alder; All tree species; Apple; Ash; Beech; Birch; Bladdernut; Boxelder; Buckthorn; Cedar; Cherry; Common grape wine; Common medlar; Common whitebeam; Cotoneaster; Dogwood; Douglas fir; Edible chestnut; Elder; Elm; English ivy; European Hornbeam; European mountain ash; Ex-Robinia; False Cypress; Fir; Forsythia ; Framire; Giant sequoia; Ginkgo; Hackberry; Hawthorne; Hazel; Hemlock; Holly; Hophornbeam; Horse chestnut; Japanese Pagoda tree; Juniper; Larch; Leyland cypress; Lilac; Linden, Lime; Magnolia; Mulberry; Oak; Olive tree; Pear; Pine; Plane; Poplar; Privet; Redwood; Rhododendron; Rose; Serviceberry; Southern Catalpa; Spindle; Spruce; Thuja; Tree-of-heaven; Walnut; Wild service tree; Willow; Yew;
Leaf; Needle; Stem; Shoot/Twig/Branch; Root;
Ozone: even in high dosage (on slopes of mountains loaded by industrial aerial pollutants) not defined as an agent weakening the trees (even loss in increment doubtful); longtime effects and combined effects with other agents unknown. sulphur dioxide, fluor hydrogen and chloric hydrogen: high doses cause decline of plants in the surrounding of emission sources.
Further information: the BFW operates an Austria-wide bio-monitoring for Norway spruces and pines (ca. 1500 trees/year) to assess immissions (Bioindikatornetz).
Curative measures None possible; in the vicinity of emission sources use of tolerant species for afforestation. Examples for immission-tolerant species: sulphur dioxide – Cedar, Sycamore maple, Edible chestnut, Elderberry, Thuja, Plane, Black pine; fluor hydrogen – Common alder, Thuja, Oaks, Planes, Willows