Sustainable and profitable control of invasive plant species by small ruminants
Both overgrazed small ruminant rangeland and invasion of aggressive vegetation are environmental concerns in the southeastern USA, St. Croix, and Puerto Rico. This project proposes to address plant:animal interface concerns that will contribute to resolving both issues by expanding the use of small-scale commercial flocks to control invasive weeds. How this is done effectively, on what species and at what cost will be addressed in five representative locations throughout the southern SARE region. Intensive, short-duration goat/sheep browsing (ISDGB) techniques for controlling weeds is the goal. In addition, the presentations and publications produced should encourage the commercialization of ISDGB by small ruminant farmers and managers of land with invading vegetation.
1) Develop ISDGB trials that address flock owner/landowner questions and serve as local demonstrations of this method for environmentally sustainable invasive plant control.
2) Research specific plant:animal interface issues that will develop into the techniques that effectively control of permanently eradicate invasive plants in each environment and for each species, including stocking rates, seasonal vulnerability, browsing duration, and negative effects on both native vegetation and flock performance.
3) Develop farmer-to-farmer contacts, demonstrations, brochures, popular press articles, web pages, and refereed articles to foment greater commercial application of ISDBG in the region.
4) Assist both landowners and goat/sheep flock mangers in determining equitable cost sharing (economics) for the commercial application of ISDGB.
Group: Project meetings and discussions were held with team members in conjunction with a Southern Consortium for Small Ruminant Parasite Control meeting in Virginia and a New Orleans American Society of Agronomy meeting.
Texas AgriLife Research
Third-year data was collected from an on-station trial using producer-acquired goats browsing hardwoods dominated by an understory of greenbriar (Smilax spp.). Two brush-management treatments, three stocking rates, and four post-ISDBG vegetation treatments were superimposed. One off-station location (private ranch in Brown County) has had brush control treatments applied through 2008 (target species mesquite, Prosopis juliflora var. glandulosa) for an on-farm trial that focuses on mechanical and chemical control methods in conjunction with ISDBG. Data from both trials will be collected in 2008. Two-year data from the greenbriar trial was prepared by Dr. Lisa Boggs, visiting scientist from Southwestern Oklahoma University, for the Southern SARE meeting entitled “Got Weeds? Get goats!!”
Our project SARE web site was updated as information came in from the other sites and can be viewed at:
The 2006 video of the ISDBG, created by the Texas AgriLife Extension can still be viewed at:
Fort Valley State University:
Sheep were used to control kudzu (Pueraria lobata, a climbing leguminous invasive found throughout the southeastern USA) in an open field, specifically looking at the effect of repeated browsing versus single-application of ISDBG. Preliminary analysis of the results indicates that sheep are very effective at controlling the growth but that destruction of the plant may require repeated heavy grazing as well as some follow-up using an herbicide to kill plants weakened by browsing. These herbicide applications, ISDBG or herbicide/ISDGB regimens will be studied in 2008.
Plant samples and data from the on-farm and on-station studies feeding corral vine (Antigonon leptopus, an invasive ornamental prevalent on most Caribbean islands) to St. Croix hair sheep were analyzed in the lab and statistically, respectively. These results have been disseminated to producers. A follow-up study replacing 0, 25 and 50% of the diet with the woody legume tantan (Leucaena leucocephala, another invasive prevalent throughout the islands, very high in protein but also containing toxic mimosine) has been planned for 2008.
In 2006, goats were rotated back and forth between two grazed plots of perennial peanut. They were moved when they had consumed everything in the plot and just before they started pulling up the peanut rhizomes. If left in the plots too long they would begin digging up or pulling up the rhizomes. Apparently the rhizomes are very palatable. In 2006 the Round-up wicking treatment gave the best weed control, goat grazing second best, and mowing last.
In 2007 the weather and rainfall was much better for perennial peanut production. By June the plots were producing more forage than the goats could eat. The goats selected peanuts over the undesirable forbs. Although the goats did graze the weedy forbs to some extent, they did not weaken the stand at all. Results for 2007 suggested that Round-up wicking gave the best weed control followed by mowing. Goat grazing provided essentially no control in this high-rainfall at the light stocking rate. The trials will be conducted one more year as designed.
University of Puerto Rico:
In 2007, a study in the Lajas Valley of Puerto Rico targeted leucaena (Leucaena leucocephala Lam. de Wit). Fifteen year-old trees of leucaena (>50%)-mixed with guineagrass were cut to ground level and leucaena allowed to sprout back to 100-cm and intensively stocked with 12 mature goats for a 12 mo period. Goats were removed after all the leaves and twigs were consumed. Leucaena re-sprouts were counted on 10 marked areas prior to introducing goats.
Leucaena was not affected by intensive stocking with goats. Despite extensive damage to leucaena stems, re-sprouts occurred from the crown and were ready for browsing within 28 d, even during dry periods.
Also in 2007, a study in Gurabo targeting climbing mimosa, locally called casta (Mimosa casta), covering 100% of area were fenced in 4 replicates and stocked with 10 mature goats for 7-10 d until all leaves and twigs of casta were consumed. Goats consume leaves and twigs of casta readily before consuming the grass component. There was 50% reduction on climbing mimosa during a 6-mo period. Sites are continuously monitored to assess recovery rate of these legumes and the increase in proportions of grass component in the plots.
Impacts and Contributions/Outcomes
As we approach the end of our grant, land-owner interest in using ISDGB for controlling invasives is growing. Web site hits, phone calls and e-mails are on the increase at all five locations. For example, based on the 2006 results on control of Albizia, biological control using goats has increased in Puerto Rico. What we need to do as a group is to assist land-managers and small-flock owners as they seek commercial ways of incorporating this as an additional income-generating activity off-farm.
Fort Valley State University
University of Puerto Rico
USVI Agricultural Experiment Station
University of the US Virgin Islands