Application method and timing of gibberellin A4/7 treatments for increasing pollen conebud production in southern pines

Abstract

In 4 different years' experiments with loblolly (Pinustaeda L.), slash (Pinuselliottiielliottii Engelm.), and longleaf (Pinuspalustris Mill.) pine, timing of gibberellin A_4/7 (GA_4/7) treatments was critical for optimal promotion of pollen conebuds. Two or three biweekly treatments given at strategic times were equivalent to six given from May to August. July to August applications best promoted pollen conebuds. Using the cationic surfactant Aromox C/12, aqueous foliar sprays of 200 mg/L of GA_4/7 were more effective than ethanolic topical bud treatments for pollen conebud induction in slash pine. Addition of naphthaleneacetic acid enhanced the GA_4/7 effect in loblolly pine but diminished it in slash and longleaf pine.