EFFECT OF THINNING ON SIZE OF ´GOLDEN DELICIOUS´ AND ´DELICIOUS´ APPLES ESTABLISHED IN CENTRAL MEXICO

To increase the size of ‘Golden Delicious’ and ‘Delicious’ apples produced in an adult orchard established in the highlands of Queretaro State in central Mexico, several chemical thinners (NAA at 5-10 mgL^-1, carbaryl at 400-600 mgL^-1, and BA at 50-75 mgL^-1), as well as manual thinning at two fruits per cluster, were evaluated. All the treatments were realized when the diameter of the fruit had reached 10-15 mm. Fifty eight days after full bloom (DAFB), a significant increase in the diameter of the fruit was observed in ‘Golden Delicious’ manually thinned, treated with BA at 75 mgL^-1 and with carbaryl at both of the doses evaluated, which didn’t occur with either dose of NAA. At ripening, only carbaryl at 600 mgL^-1 increased the size of the fruit. In contrast, none of the treatments affected the diameter of the fruits of ‘Delicious’ 58 DAFB. However, at ripening, a significant increase in fruit size could be observed with manual thinning, BA at 50 mgL-1, and with carbaryl (at 400 and 600 mgL^-1). We conclude that only carbaryl at 600 mgL^-1 was able to enhance the size of ‘Golden Delicious’ apples, whereas in ‘Delicious’ carbaryl at either dose rate, manual thinning and the hormonal product BA, all resulted in equally efficient thinning.