Citrus Fruit Abscission Induced by Methyl-jasmonate

Methyl jasmonate (MJ) was tested as a potential abscission chemical to enhance mechanical harvest of `Hamlin' and `Valenica' orange [ Citrus sinensis (L.) Osb.]. In field experiments, a solution of 1, 5, 10, 20, or 100 m m MJ was applied either as a stem wrap to individual fruit or as a spray to entire trees or canopy sectors. Solutions of 10, 20, and 100 m m MJ resulted in significant and consistent reduction of fruit detachment force and caused fruit drop within 7 to 10 days. Fruit loosening was preceded by an increase in the internal ethylene concentration of fruit similar to that of other experimental abscission compounds. While concentrations of 10 m m and less caused no or negligible phytotoxicity, solutions exceeding 10 m m MJ induced unacceptable levels of leaf abscission.