Volatile Organic Compounds from Entomopathogenic and Nematophagous Fungi, Repel Banana Black Weevil (Cosmopolites sordidus)

SIMPLE SUMMARY: Banana cultivation is crucial in all the tropical countries of the world. Banana weevil (Cosmopolites sordidus) is a coleoptera whose larvae feed on the corm of the plant making tunnels on the inside. Tunneling causes reductions in crop yield due to the loss of plants, by decaying or breakage of rhizomes and reduces the weight of the bunches. Banana weevil in Spain is present in almost all the islands of the Canary archipelago, so it is important to control this pest. This control is carried out by means of preventive or natural techniques, removing infected banana plants or by using traps with aggregation pheromones or kairomones. A sustainable alternative would be the use of biological control agents isolated and evaluated beforehand. To this end, laboratory tests have been carried out on the study of the behavior of the banana weevil with volatile compounds naturally present in fungi isolated from the banana crops of Tenerife. Laboratory tests indicated that the compounds repel banana weevil and mask the attractive activity of kairomone. The implementation of the results for the management of the pest could produce advancements in the agrobiotechnological sustainability of the world banana cultivation, increasing its production. ABSTRACT: Fungal Volatile Organic Compounds (VOCs) repel banana black weevil (BW), Cosmopolites sordidus (Germar, 1824), the key-pest of banana [Musa sp. (Linnaeus, 1753)]. The entomopathogens Beauveria bassiana (Bb1TS11) and Metarhizium robertsii (Mr4TS04) were isolated from banana plantation soils using an insect bait. Bb1TS11 and Mr4TS04 were pathogenic to BW adults. Bb1TS11, Bb203 (from infected palm weevils), Mr4TS04 and the nematophagous fungus Pochonia clamydosporia (Pc123), were tested for VOCs production. VOCs were identified by Gas Chromatography/Mass Spectrometry–Solid-Phase Micro Extraction (GC/MS-SPME). GC/MS-SPME identified a total of 97 VOCs in all strains tested. Seven VOCs (styrene, benzothiazole, camphor, borneol, 1,3-dimethoxy-benzene, 1-octen-3-ol and 3-cyclohepten-1-one) were selected for their abundance or previous record as insect repellents. BW-starved adults in the dark showed the highest mobility to banana corm in olfactometry bioassays. 3-cyclohepten-1-one (C7), produced by all fungal strains, is the best BW repellent (p < 0.05), followed by 1,3-dimethoxy-benzene (C5). The rest of the VOCs have a milder repellency to BW. Styrene (C1) and benzothiazole (C2) (known to repel palm weevil) block the attraction of banana corm and BW pheromone to BW adults in bioassays. Therefore, VOCs from biocontrol fungi can be used in future studies for the biomanagement of BW in the field.