- Animals: bovine
- Animal Production: range improvement
- Pest Management: biological control, weed ecology
Several species of leaf-feeding beetles, Diorhabda spp., have been shown to be highly effective biological control agents of saltcedar in Texas and other western states. Biological control of saltcedar is a target specific and inexpensive tactic that can provide long term, sustainable management of saltcedar and is especially suitable for use in the rangelands and natural areas of West Texas.
We will implement biological control of saltcedar, a well documented, proven and sustainable control practice, by establishing populations of leaf beetles which defoliate and suppress growth and survival of saltcedar. We will establish beetles at strategic locations on west Texas ranches, monitor their dispersal and impact on saltcedar growth, and document the initial recovery of grasses and forbs as saltcedar is defoliated by beetle feeding. We will work with the Texas AgriLife Extension Service and NRCS to conduct annual field days for ranchers and land managers to learn about biological control of saltcedar and how it can provide sustainable suppression of this exotic, invasive shrub.
Project objectives from proposal:
Objective 1: Establish Self-Sustaining Populations of Saltcedar Leaf Beetles at five locations in north central Texas.
Project Accomplishments March 2010-March 2011. Saltcedar leaf beetles were collected and released at five sites in north central Texas during June-August, 2010. From 15,000- 20,000 beetles were released at each site for a total of 81,000 beetles. During surveys in October, beetles were common and had increased to numbers sufficient to defoliate saltcedar trees at two sites. At the remaining three sites, only a few beetles were present and no tree defoliation had occurred. The lack of high beetle populations at the collection site near Big Spring, TX limited the number of beetles available for release in 2010. Additional beetles will be released at these sites in 2011.
Saltcedar beetle populations did not increase or disperse in 2010 as rapidly as they did in 2009. One explanation is a large proportion of the beetle population, as pupae, may have drown as a result of the heavy and prolonged rainfall that occurred in late June and early July across much of west Texas. The pupal stage occurs on the soil surface for about 5-6 days before the adult beetle emerges. Pupae are therefore susceptible to drowning when low lying areas flood and streams and rivers overflow. Remnants of Hurricane Alex, downgraded as a tropical storm, brought heavy rainfall into the West Texas area in beginning in late June. From June 29 through July 9, rainfall occurred on 8 of these 11 days at Big Spring, TX and totaled 3.34 inches. If a large portion of the beetle population was in the pupal stage at this time, which is likely, these pupae could have drown during this period of rainfall. As saltcedar and therefore beetles occur in areas prone to flooding, this unusual rainfall event may have resulted in an overall decline in beetle populations at many sites.
Objective 2. Document Recovery of Grasses and Forbes Following Saltcedar Defoliation by Saltcedar Leaf Beetles.
Project Accomplishments March 2010-March 2011. Vegetation survey plots were established at two sites to document changes in vegetation as saltcedar declines. Baseline data were collected in October on percent cover, species composition and density and will be collected again in 2011 to monitor vegetation changes.
Objective 3. In cooperation with NRCS andTexas AgriLife Extension Service, participate in field days for ranchers, farmers, area landowners and land managers to learn about biological control of saltcedar.
Project Accomplishments March 2010-March 2011. Presentations on saltcedar biological control were made at seven conferences, workshops and meetings and attended by 465 participants, of which an estimated 290 were ranchers, farmers and landowners. Two field tours of sites where saltcedar beetles were present were held during the year and attended by about 33 participants.