Laboratory Performance and Two-Year Field Assessment of the Seed-Feeding Beetle Algarobius Prosopis Against Recruitment of Invasive Prosopis Juliflora in Oman

Mesquite [Prosopis juliflora (Sw.) DC.] is among the most problematic invasive woody plants in Oman; its prolific seed production drives spread and recruitment. We evaluated the seed-feeding beetle Algarobius prosopis (LeConte) (Coleoptera: Chrysomelidae: Bruchinae) in laboratory experiments and a two-year field comparison in Barka, South Al Batinah Governorate. Across 100 paired mature-pod samples, mean sample mass declined from 133.48 ± 5.15 g before beetle exposure to 67.02 ± 2.60 g after exposure (mean loss 66.46 ± 2.58 g, or 49.79 ± 0.19%; Wilcoxon signed-rank test, P < 0.001). Adult emergence holes averaged 15.81 ± 2.22 per sample but were not associated with mass loss (Spearman ρ = 0.118, P = 0.241). Reproduction succeeded in all four mature-pod cages and in none of four immature-pod cages (Fisher exact test, P = 0.029), and F1 adults emerged in all 90 single-pair containers provisioned with two, four, or eight mature pods, approximately 60 d after exposure. No F1 adults emerged from chickpea (Cicer arietinum L.), faba bean (Vicia faba L.), or common bean (Phaseolus vulgaris L.) in nine replicated exposures. Following release of 17,360 laboratory-reared adults at four sites, recent mesquite recruitment was not detected at any release site during two years of monitoring, whereas it was present at all three untreated control sites, particularly after rainfall (Fisher exact test, P = 0.029). These results indicate that A. prosopis can be mass-reared on mature mesquite pods and that its release was associated with reduced mesquite recruitment under Omani field conditions. Because the field comparison involved few sites and lacked pre-release seedling counts, and because non-target screening was limited to three crop legumes, the findings should be regarded as preliminary evidence justifying expanded host-range testing, seed-viability assessment, and replicated field trials before A. prosopis is incorporated into integrated mesquite management programs.