Activity of Metarhizium brunneum and Beauveria bassiana against early developmental stages of the false codling moth Thaumatotibia leucotreta

• Published in: Journal of invertebrate pathology 2020-02, Vol.170, p.107312-107312, Article 107312
• Main Authors: Mondaca, Lilach Lily, Da-Costa, Noam, Protasov, Alex, Ben-Yehuda, Shaul, Peisahovich, Alla, Mendel, Zvi, Ment, Dana
• Format: Article
• Language: English
• Subjects: Animals; Beauveria - pathogenicity; Beauveria - physiology; Egg; Entomopathogenic fungus; Host-Pathogen Interactions; Humidity regime; Larva; Larva - growth & development; Larva - microbiology; Metarhizium - pathogenicity; Metarhizium - physiology; Moths - growth & development; Moths - microbiology; Ovum - growth & development; Ovum - microbiology; Persistence; Pest Control, Biological; Pupa - growth & development; Pupa - microbiology; Thaumatotibia leucotreta; Virulence
• ISSN: 0022-2011; 1096-0805
• DOI: 10.1016/j.jip.2019.107312

[Display omitted] •Eggs of false codling moth are susceptible to Hypocrealean entomopathogenic fungi.•Young eggs are more susceptible to fungal infection than mature eggs.•Conidia persist over time and reduce egg hatch at non-optimal relative humidity.•Citrus fruits treated with conidia gained some protection from colonization by FCM larvae. This study evaluated the efficacy of two entomopathogenic Hypocrealean fungi, Metarhizium brunneum (laboratory isolate) and Beauveria bassiana (the commercial product Botanigard), for preventative control of the false codling moth, Thaumatotibia leucotreta. The mortality of eggs and first instar larvae was studied in three different assays. First, fungal virulence was examined under optimal laboratory conditions (25 °C, 85% RH) by placing T. leucotreta eggs on conidia-impregnated filter paper. One-day-old eggs and first instar larvae were susceptible to both fungi. In contrast, 5-day-old eggs (advanced embryo development) were susceptible to M. brunneum, but not to B. bassiana. The activity of both fungi against eggs was assessed under two humidity regimes: 85% RH—optimal for fungal germination, and 60% RH—the average humidity in the laboratory. Pieces of parchment paper serving as oviposition surfaces were treated with each of the fungi and introduced to gravid females at different time points after inoculation (0, 2, 7 and 14 days). Although the tested fungal species differed in their virulence to T. leucotreta eggs, both reduced hatching rate under both humidity regimes to 8.3–58.3%, compared to 71.7–83.3% in the control treatments. To evaluate reduction of T. leucotreta infestation of fruit, ‘Ori’ citrus fruit (easy peeler Citrus sinensis) were treated with each of the fungi. Eggs were placed on the fruit peels and the fruit were maintained under room conditions (25 °C, 60% RH). Between 41.7% and 54.1% of fruit in control groups were infested by the T. leucotreta larvae. Treatments with either of the fungi resulted in about 16% infestation of the fruit with larvae, a marked (3.3-fold) reduction.