Przerzedzanie zawiązków owocowych jabłoni odmiany Golden Delicious [Apple fruitlet thinning of Golden Delicious trees]

Abstract

NAA, carbaryl and ethephon were applied separately or in mixture or additionaly with SADH on the Golden Delicious trees, in five experiments, with the aim of regulating fruiting and increase fruit size. The best results were obtained after treatment with carbaryl at cone. 2500–3000 mg/L separately or with the mixture of carbaryl and NAA at cone. 1500 and 40 mg/L, respectively. These chemicals in general caused succesful thinning and increased fruit size. The lower yield was recompensed by higher quality of apples. The results after treatments with carbaryl in mixture with NAA were comparable to those after hand thinning. NAA increased of apple size effectively also, but only at cone. 40 mg/L or higher. However at cone. higher than 40 mg/L the chemical caused injuries of the leaves and youngest shoots. NAA applied separately was less effective than in the mixture with carbaryl. Ethephon at conc. 400 mg/L, applied 14 days after blooming, caused succesful thinning in general and increased fruit size but to a smaller degree than the other chemicals. However ethephon applied in mixture with NAA increased size similarly as hand thinning. In subsequent year the trees sprayed with the mixture of ethephon and NAA yielded abundantly and the apples were smaller than control onces, consequently. Ethephon applied jointly with carbaryl didn't increase the fruit size in spite of the reduction their number. The mixture of ethephon and SADH caused succesful thinning and increased the fruit size in the year of thinning. But in subsequent year the apples were smaller than in control as a consequence of higher yield.