Evaluation of side effects of growth regulators used as anti-frost in apricots and plums on fertility characteristics

Temperate zone fruit trees are subjected to the risk of spring frost damage of flowers and new growths due to returning frosts in early spring which has been repeatedly warned for. Apart from the usual techniques of mechanical control of this risk, the use of synthetic chemicals, including growth regulators, has been proposed and implemented to create a protective cover or delay the growth starting time or flowering period of fruit trees even for a few days. Our studies have shown that most of these regulators affected the fruiting behavior of fruit trees in the past years. Four chemicals with brand names Guard^®, CropAid^®, Thiofer^® and Postafert^®, which are commercially advertised as anti-frosts, were used in an experimental orchard during 2019-2020, to reduce the spring frost damage of the flowers of plum and apricot trees. The concentrations used were prepared based on instructions provided by the manufacturer. The experiment took place in field as well as in laboratory inside phytotron. The results showed the side effects of some of the applied substances for specific traits, such as pollen germination ratio, flower density per shoot length and the percentage of total soluble solids (TSS) in fruit juice. Evaluations on electrolyte leakage in flower tissues have shown their effect in reducing ion leakage. In the field experiments, the temperature drop was lethal for several days after the flowers bloomed, and the chemicals applied did not show any efficacy.