Moisture-Dependent Effects of Soil Amendments on Adult Emergence of Ceratitis capitata in Clay and Sandy Loam Soils

Late third-instar larvae of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), leave host fruit and pupate in soil; consequently, soil physical conditions and moisture can influence successful adult emergence. We examined the effects of compost, farmyard manure, biochar, and elemental sulfur under three moisture treatments referenced to 100%, 50%, and 25% of the initial field capacity of each unamended soil in two independent factorial pot experiments conducted under controlled laboratory conditions with a clay soil and a sandy loam soil. Each amendment × moisture combination had five independent replicate pots (n = 5), each receiving 20 late third-instar larvae, and adult emergence was recorded for 15 days. In clay soil, moisture and the amendment × moisture interaction significantly affected adult emergence, whereas the amendment main effect was not significant. In the unamended clay soil, adult emergence declined to 50% at 50% field capacity but remained 98% and 93% at 100% and 25% field capacity, respectively. In sandy loam, amendment and moisture main effects were significant, but their interaction was not. Biochar and farmyard manure had the highest mean adult emergence, with no significant difference between them. Across amendments, adult emergence was lower at 25% than at 100% field capacity. These results show that soil amendments do not consistently reduce adult emergence of C. capitata; the observed responses to amendment and moisture treatments may have implications for integrated pest management.