Overcoming dormancy in ‘Laetitia’ plum trees with the use of mineral oil, vegetable oil and copper sulphate

Some regions do not provide adequate chilling for growing plum trees, requiring the use of sprouting inducers, which mostly can be highly toxic to the environment. The objective of this work was to test the efficiency of copper sulphate and vegetable and mineral oils in breaking dormancy of plum trees for use in an organic production system. In the first year (2018/2019), the greatest hastening of sprouting was observed for treatments using mineral oil 2% + vegetable oil 2% (one or two applications). Moreover, all treatments using vegetable oil and mineral oil showed greater final sprouting, differing significantly from the other treatments. In the second year (2019/2020), treatments with one application of 2% copper sulfate or 1% mineral oil + 1% vegetable oil hastened sprouting, although for final sprouting at 20 days after treatments, there were no significant differences. In both years, there was reduction in catalase activity in plant buds for most treatments with mineral and vegetable oils, except for mineral oil 2% + 2% vegetable oil (1 application) in the first year. This effect was also observed for treatments with one application of 1 or 2% copper sulphate, in both crops. In both cycles, there were frequent periods of rain during flowering, which impaired fruit set, leading to inconsistent results in relation to production aspects. The highest fruit mass was verified for the treatment with an application of 2% mineral oil + 2% vegetable oil in the first year. The treatment with an application of 2% copper sulphate showed a higher number of fruits in both years. Considering the results, the effects of two applications of 2% mineral oil + 2% vegetable oil were promising and could be a viable alternative for breaking the dormancy of ‘Laetitia’ plum trees in sustainable systems of fruit production.