Foliar Ozone Symptoms
How Do I Know It's Ozone?
Ozone-induced damage in leaves of black cherry (Prunus serotina), willow (Salix spp.), yellow poplar (Liriodendron tulipifera), grape variety Chambourcin (Vitis vinifera), ozone sensitive and tolerant snap beans (Phaseolus vulgaris).
One of the most frequent questions we are asked is: "How do you know the plant damage is from ozone and not something else?" Below is a checklist of the most common ozone (O3) injury symptoms plants display. Not all plants display exactly the same symptoms, and plants can be harmed by elevated levels of O3 without displaying the damage described here-some plants may not grow as large for example, and/or may have lower seed production.
SUMMARY OF COMMON OZONE-INDUCED LEAF INJURY SYMPTOMS
This summary and photos above courtesy of Prof. John Skelly
- Begins as just a few "stipples", angular in shape.
- Stippling coloration may vary from light tan to reddish-purple to black.
- Stipple injury appears on the upper leaf surface only, the lower leaf surface remains free of injury.
- No stippling occurs in the veins or veinlets of leaves.
- Symptoms are usually more prominent on sun-exposed leaves.
- Injury increases with increasing exposure to ozone air pollution (as the summer season progresses).
- With prolonged exposure, leaves may begin to turn yellow (chlorosis) and/or leaf cells may begin to die (necrosis).
- Later in the summer season, the stipple areas can become quite prominent being dark purple, red, or tan to dark brown depending upon plant species.
- Older leaves at the base of plants show more injury, and may drop early from the plant.
In some cases it may be difficult to distinguish O3 damage from other diseases or deficiencies and it may be advisable for an expert to inspect the affected plant(s).
For photos of what ozone damage looks like in many different plants, visit these sites:
Ozone-induced leaf damage in common milkweed plants at the SLSC Ozone Garden in 2013 (above), and the progression of damage in a single leaf.
Ozone-induced leaf damage in cutleaf coneflower plants at the SLSC Ozone Garden in 2013 (above), and the progression of damage in a single leaf.