Depth of pupation of the wild olive fruit fly, Bactrocera (Dacus) oleae (Gmel.) (Dipt., Tephritidae), as affected by soil abiotic factors

Abstract

Abstract: The influence of four abiotic factors (temperature, soil type, compaction, moisture) on the pupation depth of the wild Bactrocera (Dacus) oleae (Gmel.) larvae was studied using soils sampled in the field. Two temperatures (25 and 12°C), three different soil types (alluvial deposits, soil from decaying of limestone, soil from decaying of flysch), two compaction levels (low and high) and two moisture levels (10 and 50% field capacity) were tested in a factorial experiment with a total of 96 experimental units. Five larvae were placed on the soil surface of each test container and when burrowing was completed pupae were retrieved and pupation depth was recorded. The majority of larvae pupated in the top 3 cm and the mean depth of all units was 1.16 cm. The means differed significantly depending on soil type, moisture, the temperature–soil type interaction and the soil type–moisture interaction. Larvae pupated at a greater depth in limestone than in the other two soils. Depths were greater in soils at 50% field capacity than in those at 10% field capacity. In limestone and flysch the depth was greater at 25°C whereas no differences were found in alluvial soil. Different moisture levels had diverse effects in the three soil types; in alluvial soil and in flysch the increased moisture resulted in greater values but in limestone these were slightly lower. These results can be used in developing non chemical control measures and designing efficient sampling techniques for the insect in the ground.