The effects of hydrogen cyanamide on budburst and fruit maturity of 'Thompson Seedless' grapevine

The effect of hydrogen cyanamide (H2CN2) on budburst and fruit maturity of 'Thompson Seedless' grapes was examined. Nine year old vines of cv. Thompso n Seedless grafted on R.110 rootstock and supported on overhead tendone tre llis (parral), were treated with either 2% or 4% of H2CN2, 53 and 67 d befo re expected budbreak and compared with unsprayed vines. The earliest treatm ent with 4% H2CN2 enhanced budbreak and advanced fruit maturity by 17 d. Ho wever, the same concentration applied 53 d before natural budbreak advanced the date of maturity by only 4 d. All the treatments increased significant ly the percentage of budburst compared with the control. H2CN2 had no signi ficant effect on yield, but a positive effect on fruit quality. A higher in dex of maturity was obtained by the treatment: 4% H2CN2, 67 d before budbre ak. All the treatments of H2CN2 induced more uniform budburst compared with the control. The best uniformity was obtained by the earliest spray using the higher concentration (3%).