Tolerance of Citrus Rootstocks to Preemergence Herbicides

Abstract

Seven preemergence herbicides, Lasso (alachlor), Surflan (oryzalin), Devrinol (napropamide), Solicam (norflurazon), Goal (oxyfluorfen), Treflan (trifluralin), and Ronstar (oxadiazon) all at 1.1 and 2.2 kg/ha (1.0 and 2.0 lb/A) were evaluated for weed control and phytotoxicity to Carrizo citrange [Citrus sinensis (L.) Osb. × Poncirus trifoliata (L.) Raf.], Trifoliate orange [Poncirus trifoliata (L.) Raf.] and Swingle citrumelo [Poncirus trifoliata (L.) Raf. × Citrus paradisi Macf.] citrus rootstock seedling. Goal (oxyflurofen) was most effective in controlling weeds, but was also phytotoxic to all 3 rootstocks. Surflan (oryzalin) provided satisfactory weed control (about 70%) without any phytotoxicity to citrus rootstocks but Lasso (alachlor) and Devrinol (napropamide) did not effectively control the weeds. Carrizo citrange was most susceptible to Goal (oxyfluorfen), while Swingle citrumelo was more sensitive to Treflan (trifluralin) and Ronstar (oxadiazon). Trifoliate orange was intermediate in tolerance to all herbicides. Some herbicide treatments reduced the plant height but not the trunk diameter of Carrizo citrange and Swingle citrumelo. Trunk diameter of Trifoliate orange was significantly reduced by herbicide treatments, but was unaffected in Carrizo citrange and Swingle citrumelo.