Effect of adjuvants dioctyl sulfosuccinate sodium salt and methyl oleate on the thinning effect of two fruit thinning agent

In order to explore the chemical fruit thinning system suitable for different apple varieties, naphthalene acetic acid (NAA), 6-benzylaminopurine (6-BA) as fruit thinning agents, dioctyl sulfosuccinate sodium salt (AOT) and dioctyl sulfosuccinate sodium salt + methyl oleate (AOT + MO) as tank-mix adjuvants were applied to two apple cultivars, "Yueguan" and "Longfeng". Physicochemical property determination experiments of different assistant systems were carried out to observe their impact, spreading and permeation behaviors on the surface of apple peels. Fruit quality after treatment was determined by spraying different assistant systems in combination with different concentrations of fruit removers at young fruit stage and counting inflorescence fruit set rate, flower fruit set rate, single double fruit rate, for different treatments. The results showed that adding 0.1% AOT (m/m) or 0.3% (AOT + MO) (m/m) adjuvants significantly reduced the dynamic surface tension of the solution and the contact angle at the target interface. This reduced or inhibited the splash and bounce behavior of the droplets on the peel, while promoting deposition, spreading and penetration behavior of the droplets. The addition of 0.1% AOT and 0.3% (AOT + MO) adjuvants to the oil dispersion (OD) could significantly improve the thinning effect of the fruit thinning agent. For "Longfeng" apple, 40 mg/L NAA AS + 0.1% AOT (m/m) treatment shown no difference with artificial thinning, significantly improving the fruit quality, which was better than artificial thinning. For "Yueguan" apple,150 mg/L 6-BA + 12.5 mg/L NAA OD + 0.3% (AOT + MO) (m/m) treatment matched artificial thinning, and significantly improved the fruit quality over artificial thinning.