Small Ruminants For Biological Control Of Invasive Weeds

The invasion of fallow cropland, pasture and woodland by native and non-native weeds is a common problem throughout the Caribbean and southern USA. In Florida alone, 29% of non-cultivated plants are classified as non-native. Coral vine (.Antigonon leptopus), cogongrass {Imperata cylindrica), Japanese climbing fern (lygopodium japonicum), and leucaena (leucaena leucocephala) are well-documented examples of non-natives that have become widespread invasive species in the Caribbean. The use of intensive, short duration goat/sheep browsing (ISDGB) may be an efficacious, remunerative, and ecologically mild form of manipulating unwanted vegetation. Growing concern about invasive plants, in conjunction with a strong small ruminant market, provides a fortuitous opportunity to combine profitable animal husbandry with biological control of weeds. Both stocking rates and rotations have proven important in reducing perennial brush by using small ruminants, but the key word is "reduction" and not "eradication". Even when heavy stocking rates force intensive browsing, goats and sheep cannot always completely destroy target species, and these can still make a comeback in subsequent years from rootstocks or soil seed banks. Timing for ISDGB or combinations of different weed control methods that include ISDBG may have to be developed to ensure long-term eradication. An additional concern is the potential damage to non-target plants, such as desirable native species. The commercial application of ISDGB requires greater knowledge, including effects of prior vegetation manipulation, season of application, stocking rates, duration of exposure, and growing conditions, all of which combine to affect the degree of successful weed control and subsequent survival of desirable native species. A consortium of researchers in Puerto Rico, St. Croix, and the southeastern USA is currently studying how best to implement ISDGB with the assistance of a Southern Sustainable Agricultural Research and Education grant.