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R.A. Neja, N.K. Dokoozlian, and N.C. Ebisuda

Field experiments conducted in 1994 (low-chill winter) and 1995 (high-chill winter) examined the effects of surfactants on the efficacy of hydrogen cyanamide (H2CN2) applied to `Perlette' grapevines (Vitis vinifera L.) in the Coachella Valley of California. In 1994, when surfactants were not used, vines treated with 1% and 2% H2CN2 exhibited similar rates of budbreak and grew more rapidly than vines treated with 0.5% H2CN2. When 1% or more of the surfactant Armobreak was used, budbreak was generally similar among all H2CN2 concentrations. The number of days after treatment required for 70% budbreak declined as H2CN2 and Armobreak concentrations were increased. Results were similar in 1995, however, budbreak was inhibited when vines were treated with 2% H2CN2 + 2% Armobreak. A separate experiment conducted in 1995 revealed that two other surfactants, Activator 90 and Agridex, had similar effects on the efficacy of H2CN2 as Armobreak. The results indicate that, when 2% surfactant is used, the standard commercial H2CN2 concentration used in California may be reduced 75% while maintaining treatment efficacy. Chemical names used: hydroxypolyoxyethylene polyoxypropylene ethyl alkylamine (Armobreak); alkyl polyoxyetheylene ether (Activator 90); paraffin petroleum oil (Agridex).

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N.K. Dokoozlian, L.E. Williams, and R.A. Neja

An experiment was conducted to examine the interaction between chilling exposure (0, 50, 100, 200, 400, and 800 hours at 3C) and hydrogen cyanamide (H2CN2) concentration [0%, 1.25%, and 2.50% (v/v)] on the budbreak of dormant grape buds (Vitis vinifera L. `Perlette') collected in late fall before the onset of temperatures ≤13C. Budbreak at 22C was most rapid for cuttings exposed to 800 chill hours and least rapid for cuttings that received no chilling. Budbreak of cuttings receiving 50 to 200 hours of chilling was similar and lagged behind that of cuttings exposed to 400 or 800 hours. Maximum observed budbreak improved with increased chilling exposure. Hydrogen cyanamide hastened the growth of all chilling treatments and increased the percent budbreak of cuttings receiving ≤400 chill hours. When cuttings were not treated with H2CN2, the number of days required for 50% budbreak declined sharply as chilling exposure increased from 0 to 400 hours. In contrast, this interval was reduced only slightly as chilling increased from 400 to 800 hours. Hydrogen cyanamide-treated buds exhibited a more gradual decline in the number of days required for 50% budbreak with increased chilling exposure. In this study, the physiological efficacy and economic benefits of H2CN2 applications diminished with increased chilling exposure.

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N.K. Dokoozlian, N.C. Ebisuda, and R.A. Neja

The effects of surfactants on the efficacy of hydrogen cyanamide (H2CN2) applied to `Perlette' grapevines (Vitis vinifera L.) grown in the Coachella Valley of California were examined in 1994 and 1995. Vines were 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, H2 CN2 was applied at 0.5%, 1%, or 2% by volume 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 vines treated with 2% H2CN2 and slowest for vines treated with 0.5% H2CN2. When 2% or 3% Armobreak was used, however, little effect of H2CN2 concentration was observed. Results were similar in 1995, but the budbreak of vines treated with 2% H2CN2 + 2% Armobreak lagged behind that of vines treated with 1% H2CN2 + 2% Armobreak. The number of days after treatment required for 70% budbreak generally declined as the concentrations of H2CN2 and Armobreak were increased. A separate experiment conducted 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 surfactants to H2CN2 solutions can significantly reduce the amount of active ingredient necessary for maximum efficacy on grapevines. Chemical names used: hydroxypolyoxyethylene polyoxypropylene ethyl alkylamine (Armobreak); alkyl polyoxyethylene ether (Activator 90); paraffin petroleum oil (Agridex).

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N.K. Dokoozlian, N.C. Ebisuda, and R.A. Neja

The effects of surfactants on the efficacy of hydrogen cyanamide (H2CN2) applied to `Perlette' grapevines (Vitis vinifera L.) grown in the Coachella Valley of California were examined in 1994 and 1995. Vines were 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 volume 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 vines treated with 2% H2CN2 and slowest for vines treated with 0.5% H2CN2. When 2% or 3% Armobreak was used, however, little effect of H2CN2 concentration was observed. Results were similar in 1995, but the budbreak of vines treated with 2% H2CN2 + 2% Armobreak lagged behind that of vines treated with 1% H2CN2 + 2% Armobreak. The number of days after treatment required for 70% bud-break generally declined as the concentrations of H2CN2 and Armobreak were increased. A separate experiment conducted 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 surfactants to H2CN2 solutions can significantly reduce the amount of active ingredient necessary for maximum efficacy on grapevines. Chemical names used: hydroxypolyoxyethylene polyoxypropylene ethyl alkylamine (Armobreak); alkyl polyoxyethylene ether (Activator 90); paraffin petroleum oil (Agridex).