Hot, humid weather with stagnant air masses may lead to ozone damage on crops. Ozone warnings were recently issued for much of New York. These warnings are intended for people with respiratory problems and let them know they should limit their outdoor activity and try to stay as much as possible in air-conditioned locations. These warning are also a good indicator that ozone damage may occur in plants.

Common ozone symptoms are small, irregular, shaped spots that range in color from dark brown to black (stipple like) or light tan to white (fleck like). These spots are found only on the upper surface of the leaf.  Very young and old leaves are less susceptible to ozone while newly mature leaves are the most susceptible. With severe damage, symptoms may extend to the lower leaf surface.

Insect feeding (red spider mite and some leafhoppers) produce flecks on the upper surface of leaves, much like ozone injury. Flecks from insect feeding are usually spread uniformly over the leaf surface while ozone flecks are concentrated in specific areas, usually most pronounced at the leaf tip and along the margins.



The most sensitive crops include: Bean, Broccoli, Muskmelon, Onion, Potato, Radish, Spinach, Sweet Corn, Tomato

Intermediate crops include: Carrot, Endive, Parsley, Parsnip, Turnip

Tolerant crops include: Beet, Cucumber, Lettuce