OZONE AND SULFUR-DIOXIDE EFFECTS ON REPRODUCTION AND HOST-PARASITE RELATIONSHIPS OF SELECTED PLANT-PARASITIC NEMATODES

The effects of air pollution on the reproduction of five species of plant-parasitic nematodes with different feeding habits and host effects were studied by exposing soybean or begonia hosts to ozone (O3) and sulfur dioxide (SO2), singly or in combination, and to charcoal filtered (control) air. Exposure of infected soybean plants to O3 and O3-SO2 mixture inhibited reproduction and development of Heterodera glycines and Paratrichodorus (Nanidorus) minor, but the increase of Belonolaimus longi caudatus was usually unaffected. Exposure of soybean host plants to SO2 enhanced the reproduction of Pratylenchus penetrans compared with that in plants exposed to the charcoal filtered air control or to O3. Foliar injury of begonia by O3 or an O3-SO2 mixture inhibited the increase of Aphelenchoides fragariae. The suppressive effects of A. fragariae were greater in leaves pre-exposed to O3 or an O3-SO2 mixture before rather than after leaves were inoculated with nematodes. The growth of nematode infested soybean plants and leaves of begonia was inhibited by O3 and the O3-SO2 mixture compared with that of similar control plants grown in the presence of nematodes and charcoal filtered air. Nodulation of soybean plants inoculated with B. longicaudatus and P. minor was suppressed by O3 and the O3-SO2 mixture. The inhibition of nodulation of soybean by H. glycines was extensive; the pollutants had no further detectable effect.