Estimation of population density, survival and dispersal rates of the West Indian sweet potato weevil, Euscepes postfasciatus Fairmaire (Coleoptera: Curculionidae), with mark and recapture methods

Estimation of the population density, survival and dispersal rates of the West Indian sweet potato weevil, Euscepes postfasciatus, was attempted in three areas of different vegetation with mark-recapture methods. Recapture was done by special traps baited with sweet potatoes. In a young sweet potato field, the population density and survival rate were estimated to be 576/441 m2 and 0.88/10-day period by the JOLLY-SEBER method and 479/441 m2 and 0.72/10-day period by JACKSON's positive method. On the other hand, in a mature sweet potato field, neither marked nor wild weevils were captured. In a study field which had recently been cleared (no vegetations), only marked insects were captured. In this field, rerecapture techniques were used to estimate the survival rate. Using the JOLLY-SEBER method and JACKSON's positive method, the estimated rates were 0.84/5-day period and 0.98/5-day period, respectively. Thus, under field conditions during winter and spring in Okinawa, both survival rate and population density of E. postfasciatus adults were high in the young sweet potato field. The results also showed that the capture rate was influenced by vegetation types. A better trapping method for mature sweet potato fields must be developed. The dispersal rate of 33 m per 5-day period in the cleared field showed high mobility of this flightless beetle under some unsuitable habitat conditions.