Mark-Release-Recapture Experiments on the Effectiveness of Methyl Eugenol–Spinosad Male Annihilation Technique Against an Invading Population of Bactrocera dorsalis

Abstract

Bactrocera dorsalis is a pest of major concern in fruit-growing areas where it is not established. Control and eradication often employs male annihila- tion technique, using methyl eugenol as an attractant (MAT-ME). We conduced a small-scale mark-release-recapture study comparing two densities of MAT-ME (“high” = 225 spots per km2; “low” = 100 spots per km2) with a control by counting males recaptured in sentinel traps baited with ME 40 m from the release point. We hypothesized that recaptures would be reduced under the two MAT treatments by equivalent amounts compared with the control, reflecting male mortality from the treatments. We found a large degree of variation in trap recaptures between replicates and treatments, and no significant difference between recaptures under the high treatment and control. Recaptures were significantly lower under the low treatment, indicating greater mortality compared with control and high. We propose the “MAT-ME saturation hypothesis” to explain this result: increasing the number of stations per square mile increases mortality of receptive males until too many stations create a high enough background of ME that the males don’t effectively follow a gradient to MAT sources. Our findings highlight that further research into the effect of increasing MAT-ME spot density on male mortality is needed.