Bioassays of a Cordyceps sp. Isolate as a Candidate Mycoinsecticide Against Bemisia tabaci MEAM1 Adults

Abstract

The whitefly Bemisia tabaci MEAM1 (Gennadius) (Hemiptera: Aleyrodidae) is a major agricultural pest that infests a wide range of crops and transmits several plant viruses, leading to significant yield losses worldwide. The intensive use of chemical insecticides for its control has contributed to the development of resistance, highlighting the need for alternative management strategies. This study evaluated the pathogenicity of a Cordyceps sp. isolate (GenBank accession: PV848091) obtained from B. tabaci adults collected in soybean fields in Bom Jesus, Piauí, Brazil. Morphological characterization and molecular identification based on ITS rDNA sequencing confirmed its taxonomic placement within the genus Cordyceps. Pathogenicity bioassays were conducted under controlled laboratory conditions by exposing B. tabaci adults to leaf discs treated with two conidial concentrations (1 × 10⁵ and 1 × 10⁶ conidia/mL). Survival was monitored daily for 9 days, and infection was confirmed by fungal sporulation on cadavers. Both concentrations significantly reduced adult survival, with final survival probabilities ranging from 25% to 50%. Median lethal time (LT₅₀) estimates were 5.0 days for 1 × 10⁵ conidia/mL and 7.0 days for 1 × 10⁶ conidia/mL, indicating delayed mortality at the higher concentration, possibly due to spore aggregation or saturation effects. These results demonstrate the pathogenic potential of Cordyceps sp. PV848091 against B. tabaci MEAM1 adults and support its evaluation as a candidate mycoinsecticide in integrated pest management programs. Future research should include dose–response bioassays, assessment of efficacy across developmental stages, and field validation.