SURFACTANTS IMPROVE THE RESPONSE OF GRAPEVINES TO HYDROGEN CYANAMIDE

The effects of surfactants on the efficacy of hydrogen cyanamide (H2CN 2) applied to 'Perlette' grapevines (Vitis vinifera L.) grown in the C oachella Valley of California were examined in 1994 and 1995. Vines we re pruned in mid-December in both years and treatments applied at 1000 L.ha(-1) the following day to dormant spurs and cordons using a hand- held spray wand. In 1994, H2CN2 was applied at 0.5%, 1%, or 2% by volu me in combination with 0%, 0.5%, 1%, 2%, or 3% by volume of the amine- based surfactant Armobreak. In 1995, H2CN2 was applied at 0.5%, 1%, or 2% by volume in combination with Armobreak at 0% or 2% by volume. In 1994, budbreak rate was highly dependent upon H2CN2 concentration when 0% to 1% Armobreak was used; budbreak was generally most rapid for vi nes treated with 2% H2CN2 and slowest for vines treated with 0.5% H2CN 2. When 2% or 3% Armobreak was used, however, little effect of H2CN2 c oncentration was observed. Results were similar in 1995, but the budbr eak of vines treated with 2% H2CN2 + 2% Armobreak lagged behind that o f vines treated with 1% H2CN2 + 2% Armobreak. The number of days after treatment required for 70% budbreak generally declined as the concent rations of H2CN2 and Armobreak were increased. A separate experiment c onducted in 1995 revealed that several surfactants varying in chemical composition, Armobreak, Activator 90 and Agridex, had similar effects on H2CN2 efficacy. The results indicate that the addition of surfacta nts to H2CN2 solutions can significantly reduce the amount of active i ngredient necessary for maximum efficacy on grapevines. Chemical names used: hydroxypolyoxyethylene polyoxypropylene ethyl alkylamine (Armob reak); alkyl polyoxyethylene ether (Activator 90); paraffin petroleum oil(Agridex).