Effects of Prickly Pear Control (Prescribed Fire x Herbicide) on Three Important Food Plants of Northern Bobwhite: An Observation

Abstract

Millions of acres of Texas rangelands have been infested by prickly pear cactus (Opuntia spp.).  Because prickly pear is perceived as a nuisance plant to livestock producers, many landowners control prickly pear through a tandem of prescribed fire and an aerial application of picloram (4-amino-3,5,6-trichloropicolinic acid).  While the effectiveness of such a practice has been documented, its effects on important wildlife food plants has received little attention.  The objective was to compare density of 3 important food plants for northern bobwhite (Colinus virgnianus) between a burned-only and burned-and-sprayed area.  A 1,198-ac pasture was burned in February 1998, and subsequently sprayed with picloram a 400-ac portion in April.  Density for ragweed (Ambrosia psilostachya), croton (Croton sp.), and snow-on-the-mountain (Euphorbia marginata) was determined by randomly sampling 40 circular plots (20 in. radius) in both treatment areas during July 1998.  Ragweed had a higher mean density in the burned-only area (19.8 plants/yd2) compared to the burned-sprayed (1.3 plants/yd2; P = 0.0001).  Croton also had a higher mean density in the burned-only area (1.6 plants/yd2) than in the burned-sprayed (0.2 plants/yd2; P = 0.02).  There was no difference in snow-on-the-mountain mean density between burn-only (0.3 plants/yd2) and burned-sprayed (0.3 plants/yd2; P = 0.5).  Because forbs represent important food plants for wildlife, further research is needed to document the immediate and long-term impacts of picloram-treated sites.