The Effect of the Bioregulators Agrispon® and Ergostim on the Vegetative and Reproductive Growth of Apples

An experiment was conducted in 1990, 1991, and 1992 in Croatia to evaluate the effect of the bioregulators AgrisponR and Ergostim on the vegetative and reproductive growth and development of the apple (Malus pumila L.) varieties Elstar and Golden Delicious. Agrispon is a non-toxic plant and mineral extract containing zeatin, triacontanol, and other components. Ergostim is an L-cysteine and folic acid derivative. Both products were applied twice, three weeks after flowering, and 10 to 15 days later the chlorophyll content of leaves increased throughout the season, while carotenoids increased during the early growth stage. Leaf growth and petiole length were both affected for Golden Delicious apples, but only petiole length was affected for the cv. Elstar. Enhanced photosynthetic activity for both products produced a significant increase in apple yield and size for Elstar in 1990, for Golden Delicious in 1991, and for Elstar in 1992. Only Agrispon significantly increased Golden Delicious yields in 1992. These bioregulators have been shown to help maximize returns from fertilizer and other off-farm investments, showing their place in sustainable agriculture systems.