Sublethal effects of different fungal isolates on Helicoverpa armigera (Lepidoptera: Noctuidae)

Tamires Doroteo De Souza,Fabricio Oliveira Fernandes,Ricardo Antônio Polanczyk,Ariadne Costa Sanches

doi:10.1186/s41938-020-00327-9

Tamires Doroteo De Souza, Fabricio Oliveira Fernandes + Show 2 more

Open Access

https://doi.org/10.1186/s41938-020-00327-9

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Abstract

BackgroundBroad-spectrum pesticides and Bt crops have been used against the cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), but their effect on the environment and the development of resistance are the main limitations for these control measures. The use of mycobiopesticides is an ecofriendly and efficient alternative. Fungicides have a wide distribution and a high genetic variability, which allows their screening for more virulent isolates. Therefore, the objective of this work was to evaluate the interactions of H. armigera larvae with Metarhizium anisopliae and Beauveria bassiana, on mortality, virulence, sublethal effects, and life table aspects.Main bodyThe isolates that caused mortality rates of H. armigera above 80% were selected for further assays. Virulence was measured by LC50 estimates, using Probit analysis to sublethal effects, and the bootstrap procedure to estimate the biological parameters: time for development, fertility, longevity, pre-ovipositional period, egg viability, and sex ratio. The H. armigera mortality rates caused by B. bassiana and M. anisopliae ranged from 45 to 100% and from 40 to 90%, respectively. Longevity, fertility, and survival rates are affected in all treatments. The pupal weight of individuals treated with fungi was lower than in the control. Deformations were observed in H. armigera pupae developed from larvae treated with B. bassiana.ConclusionThe use of sublethal concentrations of isolates of M. anisopliae and B. bassiana resulted in an adverse effect on the biological parameters of H. armigera.

Highlights

The cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), is one of the most important insect pests of cotton in the world
Mortality rates Mortality rates of 2nd-instar H. armigera caterpillars caused by the isolates of M. anisopliae and B. bassiana were different
The highest means were found at the treatments of Biological Institute of Campinas (IBCB) 425 and School of Agriculture Luiz de Queiroz (ESALQ) 860 for M. anisopliae, and IBCB 1363 and IBCB 36 of B. bassiana (Fig. 1)

Summary

Introduction

Background The cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), is one of the most important insect pests of cotton in the world. It attacks more than 200 host plants (Challa et al 2013). Selecting promising isolates to control specific insect pests is possible due to their wide distribution, high intraspecific genetic variability, and spectrum of action (Goettel et al 2010). Broad-spectrum pesticides and Bt crops have been used against the cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), but their effect on the environment and the development of resistance are the main limitations for these control measures. Deformations were observed in H. armigera pupae developed from larvae treated with B. bassiana

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