2008 Volume 43 Issue 1 Pages 37-47
Mass trapping with a synthetic sex pheromone lure to control the sugarcane click beetle Melanotus okinawensis Ohira (Coleoptera: Elateridae) was conducted in an agricultural area (81.4 ha) on Ikei Island (158.3 ha), Okinawa, Japan, with 970–1,000 traps (10.6 traps/ha) from 2000 to 2005. The total number of beetles captured by 725 traps was 22,701 in 2000, which decreased to 27.6% in 2005. Mean trap catch by 50 monitoring traps showed a similar decrease (to 26.1%) during the six-year trapping. Mean catches by 10 monitoring traps in an untreated area (Miyagi Island: 107 ha) did not decrease. Trends of population density in the area estimated by release-recapture experiments indicated a population decrease of about 90% from 2000 to 2005. Furthermore, the number of wild adults discovered on sugarcane and collected by hand in the treated area also decreased every year, by up to 86.2% by 2005. The population in the untreated area did not decrease consistently. The mating rates of females collected weekly in 2001 and 2002 were 73.9 and 85.7% in the treated area, which was slightly lower than in untreated areas (92.7 and 96.7%). We defined the male removal rate as the proportion of reduced survival duration. We estimated the male removal rate using two methods. The estimate obtained from the number of recaptured individuals was 0.345 while the estimate obtained from the difference in sex ratios between the treated and untreated areas was 0.319. These values appeared too small to explain the great reduction in population density in the treated area. Nevertheless, these results indicated that mass trapping with a high density of sex pheromone traps may effectively reduce an isolated population of M. okinawensis.
