Crop‐System Variation in Methyl‐Eugenol‐Responsive Male Bactrocera Assemblages Covaries With Geographic and Landscape Context

ABSTRACT

Methyl eugenol trapping is widely used to monitor male Bactrocera , but capture patterns can reflect crop context, geography, elevation and surrounding landscape as well as species biology. We analysed a harmonised dataset from nine apple, nine guava and nine citrus orchards in East Java, Indonesia, using nine traps per orchard in two sampling periods (486 trap‐period observations). Among 16,185 males, Bactrocera carambolae Drew & Hancock represented 57.6% of apple captures, whereas Bactrocera dorsalis (Hendel) represented 71.9% of guava and 94.8% of citrus captures. Repeated‐measures negative‐binomial models showed markedly higher B. carambolae captures in apple than in guava or citrus, while absolute B. dorsalis captures did not differ among crop systems and sampling period had no overall effect. Crop system explained substantial variation in elevation ( R ²  = 0.742), plant age and latitude. Accordingly, the crop association detected by simple PERMANOVA ( R ²  = 0.269, p  = 0.0012) weakened after conditioning on broad geography ( p  = 0.0618) or elevation ( p  = 0.0682). A pre‐specified AICc candidate set identified crop‐only as the highest‐ranked model for B. carambolae , whereas landscape‐configuration models ranked slightly above crop‐only for B. dorsalis and total captures; these rankings were not robust to leave‐one‐orchard‐out and spatial‐covariance sensitivity analyses. Bactrocera umbrosa (Fabricius) occurred in eight of nine guava orchards but was absent from citrus. These results support context‐aware trap surveillance while showing that lure‐based crop associations should not be interpreted as confirmed host use, infestation or crop damage.