Bait Response and Fruit‐Associated Abundance Patterns of Two Introduced Zaprionus Species in Tropical Orchards

ABSTRACT

Fruit‐associated drosophilids are expanding in fruit‐growing landscapes, but field information on bait response and fruit‐associated occurrence remains limited for recently introduced species. We evaluated Zaprionus indianus Gupta and Zaprionus tuberculatus Malloch (Diptera: Drosophilidae) in homestead orchards of the Agreste region of Paraíba, Northeastern Brazil. From May 2024 to April 2025, two McPhail traps per orchard were exposed monthly for 15 days, one baited with guava juice and one with hydrolysed protein, while damaged fruits at intermediate‐to‐advanced ripening stages were collected from plants and the ground. Bait response was analysed using negative‐binomial generalised estimating equations with all 120 trap exposures, including zero captures. After Holm correction, guava juice was associated with higher capture rates for Z. tuberculatus females (RR = 7.12, 95% CI 2.63–19.29), Z. tuberculatus males (RR = 7.08, 2.44–20.55) and Z. indianus males (RR = 3.64, 1.44–9.22), but not Z. indianus females (RR = 1.06, 0.53–2.12). The fruit dataset comprised 43 batches (411 fruits; 31.131 kg), and all 480 target adults emerged from guava. In guava, recovery rates did not differ between species in plant‐collected fruit (RR = 1.18, 95% CI 0.44–3.20), whereas Z. indianus had a markedly higher recovery rate than Z. tuberculatus in ground‐collected fruit (RR = 11.46, 3.00–43.72). This pattern was robust to standardisation by fruit mass. Temperature and relative humidity were positively associated with trap‐level abundance, whereas precipitation was not. More broadly, our findings show that surveillance of expanding fruit‐associated drosophilids can be strengthened by accounting for species‐ and sex‐specific bait responses and by combining adult trapping with fruit‐based evidence of successful development. Such complementary monitoring can support early detection and ecological assessment of introduced drosophilids in heterogeneous fruit‐growing landscapes.