Entomopathogens from Agricultural Soil and Their Potential to Control the Banded Fruit Weevil, Phlyctinus callosus (Schönherr) (Coleoptera: Curculionidae)

Abstract

The banded fruit weevil (BFW), Phlyctinus callosus (Coleoptera: Curculionidae), is a major indigenous pest of deciduous fruits and grapevine in the Western Cape province of South Africa. Entomopathogens are effective in controlling soil-borne and above-ground stages of insect pests. Soil samples were collected from deciduous fruit orchards and vineyards in the Western Cape, baited with mealworms to isolate entomopathogenic nematodes (EPNs) and entomopathogenic fungi (EPF), which were identified using molecular techniques and assessed for their potential as biocontrol agents of BFW adults. A correlation analysis was performed to determine the effect of soil parameters on the presence of the entomopathogens. EPNs were trapped in 12 (17 %) samples, while Heterorhabditis bacteriophora and Heterorhabditis safricana were the only two species isolated. EPF were isolated from 26 (37 %) samples baited, with 14 fungal isolates identified as Beauveria bassiana (Cordycipitaceae) and 12 identified as Metarhizium anisopliae (Clavicipitaceae) complex. Heterorhabditis bacteriophora (53 %) gave significantly higher (P < 0.05) control of adult BFW than H. safricana (37 %). Metarhizium anisopliae (79 %) gave significantly higher (P < 0.05) control of BFW adults than B. bassiana (63 %). Organic matter, magnesium and phosphorus had a negative relationship with the occurrence of EPNs. A negative relationship was also reported between the occurrence of EPF, and organic matter and potassium. The results indicated that soils from the deciduous fruit orchards and vineyards from the Western Cape contain both EPNs and EPF with potential to be used in an integrated pest management system against soil-borne and above-ground stages of BFW.