The effectiveness of helmeted guineafowl Numida meleagris (Linnaeus 1766) in controlling the banded fruit weevil Phlyctinus callosus (Schönherr 1826), and their impact on other invertebrates in apple orchards in the Western Cape Province, South Africa

Abstract

The role of indigenous vertebrate predators, especially birds, in controlling pest insects is poorly known. This study quantifies the effectiveness of helmeted guineafowl Numida meleagris (Linnaeus 1766; Aves: Numididae) in controlling the banded fruit weevil Phlyctinus callosus (Schönherr 1826; Coleoptera: Curculionidae), a pest in apple and nectarine orchards in the Western Cape Province, South Africa. The impact of guineafowl on other invertebrates and on apple crops is also assessed. Periodic counts of weevils under trunk bands showed that guineafowl did not reduce weevil numbers significantly, but suction samples indicated that weevils were more abundant in plots without guineafowl. On average only 1.07 weevils were found in 30 guineafowl crops (range 0–14 weevils). The results suggest that although guineafowl consume weevils, they have a negligible impact on large weevil populations. Other invertebrates, especially molluscs and elaterid larvae (Coleoptera) were often eaten. Guineafowl reduced insect diversity in apple orchards either directly through predation or indirectly by altering the structure of the cover plants. The damage that guineafowl allegedly cause to apples was not confirmed.