2,6-dichloro-isonicotinic acid (INA) induces resistance in green beans to the rust pathogen, Uromyces appendiculatus, under field conditions

Field trials during late summer to early spring in two consecutive years demonstrated that applying 2,6-dichloroisonicotinic acid (INA) to bean seedlings (cv. Redlands Pioneer) when they were 16 to 20 days old protected plants against rust disease caused by subsequent inoculation with Uromyces appendiculatus. Protected plants had 2-10 times fewer uredinia than control plants, and protection was sustained throughout most of the growing season (i.e. for at least 5 weeks). Treatment with 2,6-dichloro-isonicotinic acid also curtailed the spread of the disease to upper uninoculated leaves, which had 4-5 times fewer uredinia than the same leaves of control plants. There was no additional resistance gained by applying a second or 'booster' INA treatment.