OXATHIIN CHEMICALS FOR CONTROL OF BRONZING OF WHITE BEANS

Carbathiin (2,3-dihydro-5-carboxanilido-6-methyl-1,4-oxathiin) or its sulfoxide analog, carbathiin-monoxide sprayed at a rate of 2.2 kg/ha gave appreciable control of ozone injury on white beans (Phaseolus vulgaris L.). When either of the two chemicals was applied to white bean plots on 2 August 1973, 2 days before a major ozone eipsode, the amount of premature leaf drop was reduced and yields increased as compared to unsprayed checks. Spraying the chemicals after the ozone episode was ineffective in reducing ozone injury. Pyracarbolid, a related oxathiin analog, did not protect white beans from ozone injury in field trials. Benomyl sprays gave a slight reduction in premature leaf drop but did not increase yields significantly when applied just before the ozone episode in early August. None of the chemicals was effective when applied after the incident of high ozone levels. A cost benefit analysis indicated that a single carbathiin spray applied prior to high ozone levels was effective and economical for the control of bronzing of white beans.