New apple thinning agents and their combination evaluated on cultivar Braeburn
2002
Stopar, M. (Agricultural Inst. of Slovenia, Ljubljana (Slovenia)) | Zadravec, P. (Sadjarski center Gacnik, Pesnica pri Mariboru (Slovenia))
Three year's old 'Braeburn'/M9 apple trees have been sprayed with fruit thinning compounds, namely, ammonium thiosulphate (ATS) and ethephon during the period of full bloom. Furthermore, 1-naphthaleneacetic acid (NAA) and 6-benzyladenin (BA) have been applied at average fruitlet diameter 10 mm. ATS 0.5 %, BA 50 ppm and NAA 10 ppm affected slight shedding of fruitlets when sprayed separately. On one hand, the application of these chemicals slightly reduced the yield while on the other the average fruit weight and return bloom were enhanced. Ethephon 150 ppm when applied separately affected neither thinning of fruitlets in the crown nor enhanced flower bud formation. The applied combination of ATS 0.5 % (at full bloom) and BA 50 ppm (at 10 mm fruitlet diameter) or ATS 0.5 % (at full bloom) and NAA 10 ppm (at 10 mm) or tank mix spraying of NAA 10 ppm + BA 50 ppm (at 10 mm) caused relatively strong thinning, enlarged fruit size greatly and enhanced return bloom. Additionally, consecutive applications of ethephon 150 ppm (at full bloom) and BA 50 ppm or NAA 10 ppm (at 10 mm) resulted in relatively strong abscission of fruitlets in the crown and increased return bloom. However, total yield was not decreased as much as with applied combinations of ATS with NAA or BA. To sum up, all consecutive applications of two thinning agents have had stronger influence on thinning of fruitlets than separate applications of each thinning compound.
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