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: Site visits by the project coordinator in 2006 included St. Croix; discussions were held with team members in Puerto Rico and Indianapolis (American Society of Agronomy meetings). An oral presentation and proceedings article at the 2006 Caribbean Food Crops Society Meeting resulted in the following project-sponsored publication:
Muir, J.P., E. Valencia, S. Weiss, and T. Terrill. 2006. Small ruminants for biological control of invasive vegetation. Proceedings XXIV Caribbean Food Crops Society Meeting. July 9-14, San Juan Puerto Rico.
Second-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 2007 (target species mesquite, Prosopis juliflora var. glandulosa) for an on-farm trial that focuses on land preparation methods and timing of ISDBG. The on-station trial will be repeated again in 2006 while the on-farm trial will be initiated as soon as mesquite leaves out in spring 2007. Control treatments will continue for 12 more months. Preliminary data from the greenbriar trial was presented by Dr. Lisa Boggs, visiting scientist from Southwestern Oklahoma University, to her fellow faculty members. Visits by the project coordinator to FVSU, St. Croix and Mayaguez are planned for 2007 to assist with project planning and implementation. A web site has been created and can be viewed at:
A video of the ISDBG was created by the Texas Cooperative Extension and can be viewed at:
Fort Valley State University:
Preliminary data on invasive kudzu has been collected at Fort Valley in 2006, with a goat-control trial initiated in 2007. Indications are that goats readily target kudzu but that regrowth occurs and needs to be controlled with either repeated ISDGB or herbicides. These herbicide applications, ISDBG or /herbicide/ISDGB regimens will be studied in 2007.
A trial feeding corral vine (Antigonon leptopus, an invasive ornamental prevalent on most Caribbean islands) to St. Croix hair sheep has indicated acceptance by animals and fair gains. An on-farm demonstration has also indicated that sheep will eat the vines, including stems, but are less attracted to the regrowth. Both the study and the demonstration are scheduled to be repeated in 2007, with an effort to identify why corral vine regrowth appears to be less palatable to the hair sheep than older growth.
The use of sheep to control weeds under orange groves continues.
University of Puerto Rico:
Invasive legume species in the wet sites of Puerto Rico are mainly Albizia procera, climbing mimosa (Mimosa casta) and catclaw (M. pellita; formerly M. pigra). On-farm goat ISDGB trails on these invasives resulted in a 28% reduction in A. procera trees 8 months into the study, with extensive damage observed on sapling bark. During the same period mature goats were rotationally stocked on catclaw mimosa and climbing mimosa. Goats consume basal leaves of catclaw but did not little damage to the branches or stems. There was however 90% reduction on climbing mimosa. Sites are being monitored to assess recovery rate of these legumes.
Another study in the Lajas Valley of Puerto Rico targeted leucaena (also called tantan, Leucaena leucocephala). Six paddocks (25 x 25-m) were fenced. The existing 15 yr-old trees of leucaena (>50%) with an understory of guineagrass (Panicum maximum) were cut to ground level and leucaena allowed to ratoon (resprout) back to 100 cm and intensively stocked with 12 mature ewes for a 6-mo period. Animals were removed after all the leaves and twigs were consumed. Leucaena re-sprouts were counted on 10 marked areas 2-wks after ewes were removed. Leucaena was not affected by intensive stocking, but guineagrass was greatly reduced. In this study, ewes were observed to graze the grass component first and then have to be forced to consume the leucaena. This study has been changed to use mature goats (nannies) as these are more selective of the leucaena than the guineagrass.
Impacts and Contributions/Outcomes
At all locations, on-farm cooperators (both landowners suffering from weed invasion and flock managers looking for additional income generation opportunities) have become aware of the potential for ISDGB as a novel agricultural activity. Landowners are aware that goats can control invasive weeds, but they do not know how to implement this approach or how to incorporate 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