Interactions between the Entomopathogenic Fungus Metarhizium anisopliae ICIPE 20 and the Endoparasitoid Dolichogenidea gelechiidivoris, and Implications for Combined Biocontrol of Tuta absoluta

Abstract

The Integrated Pest Management (IPM) approach have been widely promoted and used for the management of native and invasive pests, while the use of various components of the IPM can have a synergetic, additive, or antagonistic effect on each other; this study evaluated the susceptibility of Dolichogenidea gelechiidivoris (Marsh) (Hymenoptera: Braconidae), to the Metarhizium anisopliae (Metschnikoff) ICIPE 20 through direct and indirect infection approaches. The effect of fungus on parasitoid longevity, survival of parasitized-larvae, preference of the parasitoid to fungal treated and untreated larvae, and percent parasitism of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) under different infection scenarios were assessed. The direct application of dry conidia to the parasitoid prior to exposure to the host, reduced D. gelechiidivoris longevity, though the infected female wasps still yielded high parasitism (over 70%). Infecting the parasitized larvae at different ages led to a respective reduction of parasitoid emergence by 35% and 23% for infection at 1 and 5 days post-parasitisation. Exposure of healthy-D. gelechiidivoris adults to a plant-sprayed with fungus did not affect their longevity, and no discriminatory host selection was observed. The highest mortality (~80%) of T. absoluta was achieved when D. gelechiidivoris and M. anisopliae ICIPE 20 were used in combination, indicating an additive impact on the target pest; however, field validation can shed more light on this outcome.

Entomopathogens and Parasitoids Allied in Biocontrol: A Systematic Review

“…Trichogramma pretiosum [ 24 , 47 , 52 ] and E. formosa [ 29 , 38 , 40 , 51 ] were the most researched parasitoids, followed by A. colemani [ 23 , 30 , 32 , 35 , 46 ], C. flavipes [ 55 , 58 ], and Diaeretiella rapae [ 18 , 43 ]. In terms of microorganisms, B. bassiana [ 17 , 18 , 24 , 26 , 32 , 33 , 35 , 40 , 42 , 43 , 48 , 51 , 52 , 54 , 55 , 57 , 58 , 59 , 60 , 61 , 63 , 64 , 65 ] was the most studied fungus, followed by M. anisopliae [ 30 , 34 , 36 , 37 , 48 , 49 , 50 , 51 , 53 , 55 , 57 , <...…”

“…Thirty-eight out of forty-nine combinations of biocontrol agents were reported as compatible [ 18 , 19 , 20 , 22 , 24 , 25 , 26 , 29 , 32 , 34 , 35 , 36 , 37 , 39 , 41 , 43 , 44 , 45 , 47 , 49 , 50 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 62 , 63 , 64 , 65 ] ( Table 1 ). Six combinations were reported as incompatible [ 17 , 27 , 28 , 42 , 51 ], often due to a lower emergence rate caused either by bad timing, direct infection, or too high dosage.…”

“…The influences of combined biocontrol agents on pest mortality were analysed in ten laboratory experiments extracted from nine studies [ 25 , 28 , 38 , 44 , 45 , 50 , 57 , 62 , 65 ]. Out of 41 observations made in these experiments, 14 reported a positive effect, with significantly higher pest mortality when biocontrol agents were combined compared to the strongest agent used alone.…”

“…Out of 41 observations made in these experiments, 14 reported a positive effect, with significantly higher pest mortality when biocontrol agents were combined compared to the strongest agent used alone. In 11 of these, the interaction was less than additive [ 25 , 28 , 57 , 65 ]. In two further observations, it was additive [ 50 ], and in one, it was synergistic [ 50 ].…”

“…We used Citavi software (version 6.11.0.0) to import the included studies. We extracted data on (1) pest, (2) control agents, (3) crop, (4) location, (5) study design, (6) evolution of pest and biocontrol agent populations, (7) crop damage, (8) crop yield, and (9) compatibility of biocontrol agents from the 49 selected articles [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 ]. Each combination of biocontrol agents was considered an experiment, leading to 1...…”