Evaluation of the Potential of Fungal Biopesticides for the Biological Control of the Seed Bug, <i>Elasmolomus pallens</i> (Dallas) (Hemiptera: Rhyparochromidae)

• Main Authors: Fredrick Fidelis Umaru, Khanom Simarani
• Format: Article
• Language: English
• Published: MDPI AG 2020-05-01
• Series: Insects
• Subjects: biological control; aflatoxin; Aspergillus flavus; Metarhizium anisopliae; insect cadaver; biocontrol agent
• Online Access: https://www.mdpi.com/2075-4450/11/5/277

<i>Elasmolomus pallens</i> is a post-harvest insect pest of groundnuts which causes severe yield loss to farmers, particularly in Africa and Asia. Resistance to synthetic chemicals has been on the rise among insects and is a constraint on insecticides regulations. In view of the drive for alternative approaches to synthetic insecticides, this study evaluated the potential of biopesticides based on entomopathogenic fungi against <i>E. pallens</i> under laboratory conditions. Fungal isolates from the bug cadaver including <i>Fusarium proliferatum</i> F1, <i>Aspergillus tamarii </i>F2, <i>A. flavus </i>F3, <i>Trichoderma atroviride </i>F4, <i>A. niger </i>F4, and <i>Metarhizium anisopliae</i> (Meschn.) Sorokin, originating from the cadaver of <i>Zonocerus variegatus </i>were screened for virulence against the bug. Adult bugs were dipped briefly in conidial concentration 1 × 10⁸ conidial mL⁻¹ and observed at 25 ± 2 °C, 80 ± 10 RH and 14: 10 L:D for 10 days. The fungal isolates caused mortality ranging from 48 to 100% based on their potential to infect and kill the bug. Five conidial concentrations (1 × 10⁴ to 1 × 10⁸ conidia mL⁻¹) were evaluated against adult bugs in the multiple-dose virulence bioassay. Lethal concentrations (LC₅₀ and LC₉₀) values of 6.75 × 10⁶and 4.42 × 10⁹conidia mL⁻¹ were obtained for <i>A. flavus</i> F3 while <i>M. anisopliae</i> had 8.0 × 10⁶ and 6.14 × 10⁸conidia mL⁻¹ respectively. Lethal time (LT₅₀ and LT₉₀) values were 3.3 and 6.2 days for <i>A. flavus</i> F3 compared to 3.6 and 5.6 days for <i>M. anisopliae</i>, respectively. Thus, <i>A. flavus </i>F3 showed potential against <i>E. pallens</i>; and can be considered as an ideal isolate for incorporation into formulations for field applications.