A standardised bioassay method using a bench‐top spray tower to evaluate entomopathogenic fungi for control of the greenhouse whitefly, Trialeurodes vaporariorum

Abstract

BACKGROUND: Bioassays evaluating entomopathogenic fungi (EPF) isolates for effective microbial control of whitefly are a fundamental part of the screening process for bioprotectants, but development of repeatable, robust bioassays is not straightforward. Currently, there is no readily available standardised method to test the efficacy of EPF on whitefly. Here, we describe the calibration and use of a spray tower to deliver a standardised protocol to assess EPF activity; the method was validated using 18 EPF from four genera in tests against greenhouse whitefly, Trialeurodes vaporariorum (Westwood).RESULTS: At 138 kPa, the sprayer delivered 0.062 mL mm −2 (620 L ha −1 ) and an even deposition of spray across the central 1590 mm 2 of the spray area. Average conidial deposition for all EPF was 252 conidia mm −2 and equivalent to 2.5 × 10 12 conidia ha −1 at an application concentration of 1 × 10 7 conidia mL −1 . Conidial deposition of a test Beauveria bassiana suspension increased with increasing application concentration. Egg laying by T. vaporariorum adults was restricted to 177 mm 2 using clip cages specifically designed to ensure that third-instar T. vaporariorum received a uniform spray coverage. Nymphs occupied 373 ± 5 mm 2 of the leaf after migrating during the first instar. Average T. vaporariorum mortality totaled 8-89% 14 days after application of 1 × 10 7 conidia mL −1 of each EPF isolate. CONCLUSION: Combining the calibrated sprayer and bioassay method provides a reliable, standardised approach to test the virulence of EPF against whitefly nymphs. This laboratory-based assay is affordable, replicable and allows the user to alter the dose of conidia applied to the target.

Endophytic Colonisation of Solanum lycopersicum and Phaseolus vulgaris by Fungal Endophytes Promotes Seedlings Growth and Hampers the Reproductive Traits, Development, and Survival of the Greenhouse Whitefly, Trialeurodes vaporariorum

“…The management of T. vaporariorum especially in protected agriculture has been successful using biological control agents such as parasitoids Encarsia formosa (Gahan) and Eretmocerus eremicus (Rose and Zolnerowich) (Hymenoptera: Aphelinidae) (Gonzalez et al, 2016); predators like Amblyseius swirskii (Athias-Henriot) (Acari: Phytoseiidae) and Delphastus catalinae (Horn) (Coleoptera: Coccinellidae) (Spence et al, 2020), and some species of entomopathogenic fungi, namely, Beauveria bassiana (Balsamo) Vuillemin, Metarhizium anisopliae (Metschnikoff) Sorokin (Hypocreales: Clavicipitaceae), and Isaria fumosorosea (Wize) Brown and Smith (Hypocreales: Cordycipitaceae) (Gökçe et al, 2005;Gonzalez et al, 2016).…”

Controlling insecticide resistant clones of the aphid, Myzus persicae, using the entomopathogenic fungus Akanthomyces muscarius: fitness cost of resistance under pathogen challenge

“…Furthermore, 20–22 even‐aged adult apterous aphids were treated in a 55 mm Petri dish with the LC 50 of A. muscarius conidial suspension. Fungal suspensions were applied with a microspray tower consisting of an acrylic cylindrical tube, a top cap and artist airbrush (HP‐SBS ECL3500 with standard nozzle, ANEST Iwata‐Medea, USA), similar to those in other EPF studies 56,57 . Precise specifications and validation of the consistency of this set‐up have been described previously 55 .…”

“…Fungal suspensions were applied with a microspray tower consisting of an acrylic cylindrical tube, a top cap and artist airbrush (HP-SBS ECL3500 with standard nozzle, ANEST Iwata-Medea, USA), similar to those in other EPF studies. 56,57 Precise specifications and validation of the consistency of this set-up have been described previously. 55 The volume and pressure settings after calibration were determined as 400 μL and 83 kPa.…”

Efficacy of Metarhizium anisopliae and (E)–2–hexenal combination using autodissemination technology for the management of the adult greenhouse whitefly, Trialeurodes vaporariorum Westwood (Hemiptera: Aleyrodidae)

“…Metarhizium anisopliae (Metschnikoff) Sorokin (Hypocreales: Clavicipitaceae) is among these entomopathogenic fungi proven to cause mortality in all stages of T. vaporariorum life cycle (16,17). However, most of the pathogenicity studies have primarily focused on the nymphal stages (9,11,(18)(19)(20)(21), where fungal formulations were mainly applied through leaf spraying and dipping methods (15,21). There are very limited studies on the adult stage of T. vaporariorum where the fungus was used as dry conidia (17).…”