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Abstract
Ten compounds applied as foliar spray were screened for reducing and delaying bolting in fall-planted carrots (Daucus carota L.). Only butanedioic acid mono-(2,2-dimethylhydrazide) (daminozide) was effective; seedstalk height was reduced and root size was unaffected. Daminozide effectiveness was greatest in weak-bolting cultivars. Two sprays of 5000 ppm, 2 weeks apart at about 4 and 2 weeks prior to natural bolting were most effective, suggesting that daminozide does not interfere in the cold temperature induction process, but rather has a delaying and inhibitory effect on the initial seedstalk elongation. Two sprays of 500 liters/ha of daminozide solution of 5000 ppm gave promising results. Root quality was improved without influencing carrot yield or dry matter content. Although (2-chloroethyl)trimethymammonium chloride (chlormequat) suppressed bolting in some experiments, it was less effective than daminozide at comparable rates and higher rates decreased yield.