Distance-dependent capture probability of male Mediterranean fruit flies in trimedlure-baited traps in Hawaii

Many countries operate regional trapping programs for the detection of exotic tephritid fruit flies, which because of their polyphagous habits pose a serious threat to fruit and vegetable crops. Detection of the Mediterranean fruit fly (medfly), Ceratitis capitata (Wiedemann), relies primarily on trimedlure (TML), a synthetic male-specific lure, yet few studies have measured the relationship between distance from TML-baited traps and the probability of male capture, and consequently the detection sensitivity of medfly trapping programs is largely unknown. The present study measured distance-dependent capture probabilities for male C. capitata in TML-baited traps using mark–release–recapture procedures. Releases were performed at distances of 25, 50, 100, and 200 m at 4 sites in Hawaii, and the resulting capture rates were used to estimate the minimum detectable population size (detection probability > 99.9%) for a trapping density of 5 TML traps per 2.59 km² (= 1 mi², the density used in California, USA). Capture rates were similar for 3 of the sites (6.5%, 3.8%, 1.1%, and 0.1% for the 4 distances, respectively) and yielded an estimated minimum detectable population of ≈ 2300 males, a value similar to that obtained in a comparable study conducted in California. For unknown reasons, capture rates were significantly lower at the remaining site (1.8%, 0.6%, 0.1%, 0.04%) and the estimated minimum detectable population was correspondingly much larger (≈ 10,000 males). Implications of these results for medfly detection programs are discussed.