Susceptibility of Selected Woody Plants to Hexazinone on South Texas Rangeland

Abstract

Grid applications of hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione] pellets at 2.2 kg ai/ha or less did not effectively control honey mesquite [Prosopis juliflora(Swartz) DC. var.glandulosa(Torr.) Cockerell ♯3PRCJG], blackbrush acacia (Acacia rigidulaBenth. ♯ ACARI), lotebush condalia [Condalia obtusifolia(Hook.) Weberb. ♯ CNCOF], granjeno (Celtis pallidaTorr. ♯ CETPA) or twisted acacia [Acacia tortuosa(L.) Willd.] growing as mixed stands on clay loam or clay soils. Efficacy of hexazinone apparently was affected little by variation in rainfall ranging from 35% less to 51% greater than the long-term average during the year of application. Apparent mortality of honey mesquite, granjeno, and lotebush condalia was increased by increasing the application rate from 2.2 to 4.5 kg/ha on clay loam soils. Control of honey mesquite, blackbrush acacia, and twisted acacia with 2.2 kg/ha was better when applied to sandy clay loam than to clay soils.