Influence of huisache (Acacia farnesiana) canopy on herbaceous forage production, silverleaf nightshade (Solanum elaeagnifolium) presence, and grazing economics in South Texas rangelands.

In South Texas, huisache populations have been increasing, and improved control efforts are being explored. The goal of this project was to study the impacts of huisache (Acacia farnesiana) on forage resources in South Texas. To accomplish this, I studied the effect of huisache canopy on understory herbaceous forage production and composition, huisache canopy influence on the presence of silverleaf nightshade, and the costs and benefits of herbicide treatments on huisache-invaded pastures. I conducted the study at four sites located in the Coastal Bend region of Texas: Kleberg, Refugio, San Patricio, and Victoria Counties. The results show that huisache canopy had no effect on total above ground herbaceous biomass. I also found that: silverleaf nightshade abundance decreased as distance from huisache trunks increased, with 1.63 plants per m2 at 0-0.5m, 1.02 plants per m2 at 0.5-1m, and 0.47 plants per m2 at distances >1m; and at current levels, the added cost of treating huisache could not be justified for stocker operations across all sites: Refugio Co. experienced a loss of $82.44/acre, San Patricio Co. experienced a loss of $102.20/acre, Victoria Co. experienced a loss of $81.68/acre, and Kleberg Co. experienced a loss of $212.60/acre when the costs and benefits of treating huisache were simulated. These results provide insight that at current levels of huisache, control efforts will provide little benefit with respect to herbaceous forage production or being economically justifiable but may result in lower amount of silverleaf nightshade being observed on the sites.