Pueraria phaseoloides eradication from Santa Cruz Island (Galapagos)
The feasibility of eradication of an introduced plant depends principally on the costs, which in turn depend on the biology, detectability and distribution of the plants as well as other logistical considerations. Information from prior eradication attempts could assist in estimating costs, but there is little information available on the costs of eradication attempts of a specific plant. It therefore seems important to report tactics and costs, in order to contribute to general analyses of the factors that influence costs and feasibility. Since monetary costs change, such a report should not only present financial costs, but also the elements in more stable units such as person-hours, transport (distances) and quantities of herbicide or other material.
Pueraria phaseoloides (Fabaceae) is a close relative of the very invasive P. lobata. It is native to tropical Asia and is considered a noxious weed and a quarantine weed by the Global Compendium of Weeds. The plant is widely grown in tropical Ecuador for ground cover in orchards and as a forage plant and soil improver. A bag of seeds of the plant was voluntarily imported to Santa Cruz Island by a farmer in 1995 and sown in a single pasture in an agricultural zone. A few of these plants produced flowers by 1996. The plant was noticed by the Charles Darwin Research Station in March 1996 and when the potential danger of the species was explained to the farmer he agreed to allow the eradication of the plant. The project schedule was as follows:
- March 2006: discovery and initial consultations
- April 2006: search of the species in the field and surroundings, enquiries made to farmers. The plant was only found in the recorded field, application of 41% glyphosate salt from a backpack sprayer was performed.
- April-May 1996: meetings to arrange the eradication and approval by the regional authority.
- Spring 1996, 1997: complete searches of the field, spraying of the plant found. Last plant seen in September 1997.
- March 1998, June 1999, January 2001: complete searches of the field, no plant found.
The total cost of the eradication project was approximately 1600 USD (≈1200 EUR) over five years. About 80% of the total cost was 108 person-hours of labour, 75% of which were spent searching for the plant. It appears that the searching of plants in the field always requires a substantial part of the budget in eradication projects. Eradication was particularly relevant in this case as the place of introduction was clearly identified, was restricted to a small area and was accessible. Pueraria phaseoloides is now considered eradicated from Santa Cruz Island.
A Global Compendium of Weeds. http://www.hear.org/gcw/alpha_select_gcw.htm
Tye A (2007) Cost of rapid-response eradication of a recently introduced plant, tropical kudzu (Pueraria phaseoloides), from Santa Cruz Island, Galapagos. Plant Protection Quarterly 22(1), 33:34.