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 yea rs demonstrated that applying 2,6-dichloroisonicotinic acid (INA) to b ean 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 u redinia than control plants, and protection was sustained throughout m ost of the growing season (i.e. for at least 5 weeks). Treatment with 2,6-dichloro-isonicotinic acid also curtailed the spread of the diseas e to upper uninoculated leaves, which had 4-5 times fewer uredinia tha n the same leaves of control plants. There was no additional resistanc e gained by applying a second or 'booster' INA treatment.