The efficacy of chemical and mechanical thinning strategies for 'African Rose¿' Japanese plum (Prunus salacina Lindl.)
Japanese plum production is a significant component of the South African deciduous fruit industry. Thinning is an important practice in plum production and there is a huge need for new thinning strategies. The purpose of this study was to evaluate new chemical thinning strategies on 'African Rose'. The chemicals evaluated were 1-aminocyclopropane-1-carboxylic acid (ACC) at 150, 300 and 500 µL L-1 in the 1st season and 400, 600 and 800 µL L-1 in the 2nd season, and 6-benzyladenine (6-BA) at 100 or 300 µL L-1 in the 1st season and 100 µL L-1 in the 2nd season. 6-BA was included to prevent ACC-induced leaf drop. ACC was also combined with mechanical thinning utilizing the Darwin 300 and hand thinning during bloom included as treatment.All the foliar applications were made when the average fruitlet size was 8-10 mm. ACC consistently reduced the commercial hand thinning requirement in both seasons. In the second season, there was a linear decrease in yield efficiency as the ACC rate increased, while a quadratic response was seen in fruit size with the two higher rates inducing larger but similar fruit size. The combination treatment of ACC (600 and 800 µL L-1) and the Darwin 300 thinned more aggressively, improved fruit size and shifted harvest distribution earlier without decreasing the yield efficiency compared to the control. The recommended ACC rate for 'African Rose' would be 600 µL L-1. No leaf drop/phytotoxicity or broken stones were recorded.
Theron, K.I., Steenkamp, H., Lötze, G.F.A. and Steyn, W.J. (2016). The efficacy of chemical and mechanical thinning strategies for 'African Rose¿' Japanese plum (Prunus salacina Lindl.). Acta Hortic. 1138, 61-68
1-aminocyclopropane-1-carboxylic acid (ACC), 6-benzyladenine (6-BA), thinning, yield, fruit quality