Abstract
This paper investigates 71 isolates of two genera of entomopathogens, Metarhizium and Beauveria, and a biostimulative genus Trichoderma, for their ability to infect yellow mealworms (Tenebrio molitor) and to stimulate maize (Zea mays) growth. Fungal origin, host, and isolation methods were taken into account in virulence analysis as well. Isolates Metarhizium brunneum (1154) and Beauveria bassiana (2121) showed the highest mortality (100%) against T. molitor. High virulence seems to be associated with fungi isolated from wild adult mycosed insects, meadow habitats, and Lepidopteran hosts, but due to uneven sample distribution, we cannot draw firm conclusions. Trichoderma atroviride (2882) and Trichoderma gamsii (2883) increased shoot length, three Metarhizium robertsii isolates (2691, 2693, and 2688) increased root length and two M. robertsii isolates (2146 and 2794) increased plant dry weight. Considering both criteria, the isolate M. robertsii (2693) was the best as it caused the death of 73% T. molitor larvae and also significantly increased maize root length by 24.4%. The results warrant further studies with this isolate in a tri-trophic system.
Highlights
71 fungal isolates were analyzed for their virulence against T. molitor (Table 1)
Only M. robertsii and M. guizhouense were isolated with Tenebrio as bait, while with Galleria as bait approximately half of the isolates were B. bassiana and the other half belonged to the genus Metarhizium
There are some reports where B. bassiana was recovered more frequently when Galleria was used as bait, while Tenebrio bait resulted in more frequent isolation of Metarhizium species [28,30,31]
Summary
Entomopathogenic fungi are primarily known for their ability to parasitize insects and kill or severely harm them [1,2,3]. Fungi of the hypocrealean family Cordycipitaceae include important entomopathogens, of which certain species of Metarhizium, Beauveria and Isaria are most studied. The use of these typically facultative parasitic fungi as biopesticides is prevalent due to the wide range of target hosts and their ability to complete their life cycles independently from insect hosts [4]. Entomopathogens can colonize the rhizosphere and plant tissues as endophytes and act as plant growth promoters [5,6]
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