Organosilicone Surfactants Sometimes Reduce Corrected Soluble Solids in Processing Oranges Treated with EcoLyst

Abstract

EcoLyst (a formulation of N-N-diethyl-2-(4-methylbenzyloxy) ethylamine hydrochloride, at 0.034 g·ml ^-1), is a plant growth regulator that was reported to increase soluble solids concentration (SSC) in juice oranges by 0.6 to 1.2˚ Brix in initial research and development trials. In our previous report, replicated field experiments largely failed to confirm the excellent early reports, despite numerous trials at different material rates and spray timings conducted over many locations and several years. Based on initial reports, all of these trials had included Silwet L-77 adjuvant at 0.05%. A single trial on ‘Valencia’ ( Citrus sinensisL.) in 2000 compared EcoLyst application with numerous surfactants, including a no surfactant treatment and a non-treated control. At harvest, the exclusion of surfactant resulted in significantly higher SSC than in the control and treatments that included surfactants. To test the hypothesis that surfactant use may be compromising EcoLyst efficacy, experiments compared EcoLyst response with and without Silwet L-77 on 6 blocks of ‘Hamlin’ and 3 blocks of ‘Valencia’ sweet oranges, all in commercial orchards. Only two trials, one in each year of the study, showed an increase in SSC from EcoLyst treatment relative to non-treated controls. More interestingly, in these two trials and in one additional trial, inclusion of Silwet L-77 with EcoLyst resulted in a significant SSC reduction relative to EcoLyst alone. This suggests that the surfactant was sometimes deleterious to fruit SSC development and/or EcoLyst enhancement of SSC.