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Inadequate winter chilling periodically becomes a serious problem for the commercial peach industry in the Southeast, especially along the Gulf Coast. A number of countries around the world are using hydrogen cyanamide (Dormex-SKW) to replace lack of chilling in peaches and other fruit plants. Studies were conducted over 3 years (1990-1992) to evaluate the effects of hydrogen cyanamide on replacing lack of winter chilling in 'Ruston Red' peach, (850 hour chill requirement). Findings indicated full tree sprays in early fall and late winter (after buds had become active) caused excessive bud thinning and crop reduction. Applications made when 65 to 85% of chilling requirement was satisfied (no visible bud activity) were very effective at concentrations of 0.5 to 1.0% V/V of 49% Dormex. Rates above 2% were very toxic causing crop loss. Dormex effectively replaced a shortage of 265 chilling hours of 'Ruston Red' during one season resulting in full cropping while controls failed to crop.

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Lack of winter chilling can be a serious problem for commercial peach producers in the Southeast. Studies were conducted over 3 years (1989-91) to evaluate the effects of hydrogen cyanamide (Dormex-SKW) on replacing lack of winter chilling on 7 varieties of peaches. This study specifically reports on the effects of hydrogen cyanamide on 'Ruston Red' peach, a 850-hour variety.

Results from 1990 studies using whole tree sprays to the point of runoff indicated a problem with the efficacy and phytotoxicity. In 1991, a combination of hydrogen cyanamide (49%) rates (0, 0.5, 1, 2, and 4% V/V) and timings (0, 25, 50 and 75% of chilling level) were evaluated using 7-year-old 'Ruston Red' peach trees. Only 590 hours of chilling at 7.3°C and lower were accumulated at this site. Rates of 0.5 75% (actually only 70%) chilling level induced full cropping while control trees produced practically no crop.

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Lack of winter chilling periodically becomes a serious problem for commercial peach producers in the Southeast, especially along and near the Gulf Coast areas. Studies were conducted over 3 years (1989-1991) to evaluate the effects of hydrogen cyanamide (Dormex - SKW) on replacing lack of winter chilling in 7 varieties of peaches.

Initial findings using whole tree sprays to point of runoff indicated a problem with efficacy and phytotoxicity. A combination of hydrogen cyanamide rates (0, .5, 1, 2 and 4% V/V) and timings (0, 25, 50 and 75% of chilling level) were evaluated in 1991. Rates above 2% were phytotoxic. Rates of 0.5 to 1.0% were safe and effective when applied at 75% chilling.

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