Susceptibility of Selected Woody Plants to Pelleted Picloram

Abstract

Picloram pellets, aerially applied at 1.1 kg/ha in the spring to South Texas mixed-brush, effectively controlled spiny hackberry and pricklypear, and 2.2 kg/ha temporarily controlled blackbrush acacia. However, agarito, desert yaupon, lotebush, Texas persimmon, and whitebrush were only slightly susceptible to soil applications of picloram, and honey mesquite and creeping mesquite were tolerant. Range site exerted a significant influence only with initial defoliation of twisted acacia. Although canopy reduction of twisted acacia after one growing season was higher on Shallow than on Rolling Blackland or Claypan Prairie range sites, it was apparently only moderately susceptible to pelleted picloram. Shredding prior to pellet applications did not improve the level of brush control compared to applying the picloram to undisturbed brush stands. There was no consistent difference in brush control within an application rate between 5% or 10% active ingredient formulations of picloram pellets.