Mineral and vegetable oils as effective dormancy release agents for sustainable viticulture in a sub-tropical region

Increasing restrictions on the use of agrochemicals in agriculture is a major limiting factor for grapevine (Vitis vinifera L.) growers, especially with respect to the use of hydrogen cyanamide as a bud dormancy-releasing compound, which is usually necessary in sub-tropical regions. In this context, a trial of the cultivar ‘Carmem’ was carried out in a commercial vineyard located in Paraná State, Southern Brazil, with the aim of developing an environmentally friendly and economically viable bud-break treatment. The following treatments were applied over two consecutive years: (i) control (water); (ii) 2% (v/v) vegetable oil (VO); (iii) 2% (v/v) mineral oil (MO); (iv) 2% (v/v) VO + 2% (v/v) MO; or (v) 3% (v/v) hydrogen cyanamide (HC). In both years, treatments (iv) and (v) increased bud-break percentages by a similar extent, from 24-25.0% to 60-95%. Both treatments also increased the number of berry clusters and yield, from 0.9-1.3 kg to 3.3-4.6 kg per vine, and decreased catalase activity in buds until 24 h after treatment. It appears that treatment (iv) could provide a substitute for the use of 3% (v/v) hydrogen cyanamide in viticulture in the sub-tropics, and could be a sustainable alternative based on lower cost and environmental impact.