Potential of the Parasitoid Tetrastichus howardi (Olliff, 1893) (Hymenoptera: Eulophidae) on the Control of Helicoverpa armigera (Hübner, 1805) (Lepidoptera: Noctuidae)

Juliana Simonato,Mirian M Kubota Grigolli,José F J Grigolli,Ivana F Da Silva,Harley N De Oliveira

doi:10.5539/jas.v12n7p146

Juliana Simonato, Mirian M Kubota Grigolli + Show 3 more

Open Access

https://doi.org/10.5539/jas.v12n7p146

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Abstract

Helicoverpa armigera (Hubner, 1805) (Lepidoptera: Noctuidae) is an insect pest that attacks several cultures and has been a cause of concern in Brazil. The objective of this study was to evaluate parasitism in pupae and caterpillars of H. armigera by Tetrastichus howardi (Olliff, 1893) (Hymenoptera: Eulophidae), in laboratory, as well as checking if T. howardi parasitoid has the ability to locate and infect H. armigera. In the laboratory, pupae of H. armigera and Diatraea saccharalis (Fabricius, 1794) (Lepidoptera: Crambidae) were exposed to 15 T. howardi females for 24 hours. Third, fourth and fifth instars of H. armigera were exposed to three T. howardi females for 24 hours. In the field experiment, cages were installed. Ten caterpillars of the fifth instar of H. armigera were released in each cage and waited for the necessary period for them to soak in the soil. After this period, 150 T. howardi females were released in each of four cages and in one cage there was no release of parasitoids. In the laboratory, the percentage of parasitized and emergent pupae was 100% in both hosts. The life cycle of T. howardi in H. armigera pupae was 15 days, and for D. saccharalis it was 16 days. The progeny was significantly larger for the host H. armigera (689.00) compared to D. saccharalis (358.27). The sex ratio was 0.91 and 0.87 for H. armigera and D. saccharalis, respectively. The longevity of males (25.60 days) and females (26.95 days) in the treatment with H. armigera differed from the treatment with D. saccharalis, which was 21.70 days for males and 22.95 days for females. For the experiment with H. armigera caterpillars, it was found that only two caterpillars from the fifth instar were parasitized with emergence of parasitoids in the pupal phase, with a progeny of 81 individuals; egg-adult cycle was 19.5 days; sex ratio of 0.88; male longevity was 19.6 days and for females 20.3 days. Despite the high rate of parasitism of T. howardi in H. armigera pupae in the laboratory, the same did not occur for caterpillars. In the field evaluation, of the total of 50 caterpillars released in the cages, 34 pupae were collected. Of these, 31 pupae had emergence of the H. armigera moth. No parasitism by T. howardi was found in H. armigera pupae. Further studies should be conducted to evaluate T. howardi parasitism in H. armigera pupae under field conditions.

Highlights

As Brazil has reached records of soybean Glycine max (L.) Merrill production with each harvest, it is the second largest soybean producer in the world, with great prospects of being the largest producer (Lima et al, 2019)
In Brazil, the natural occurrence in H. armigera caterpillars of Archytas marmoratus (Townsend, 1915) (Diptera: Tachinidae) (Guerra et al, 2014) and Campoletis sonorensis (Cameron, 1886) (Hymenoptera: Ichneumonidae), A. incertus (Macquart, 1851) (Diptera: Tachinidae) parasitoids has been recorded, associated with H. armigera, in which the larval parasitism rate was higher than 41% in areas of structured cotton refuge, without the use of chemical insecticides (Luz et al, 2018)
Helicoverpa armigera pupae (n = 30) with a mass between 0.328 and 0.418g and D. saccharalis pupae (n=30) with a mass between 0.187 and 0.228g, both 24 hours after pupation were individualized in flat-bottomed glass tubes (8.5 × 2.5 cm) and exposed to parasitism by 15 T. howardi females up to 24 hours old

Summary

Introduction

As Brazil has reached records of soybean Glycine max (L.) Merrill production with each harvest, it is the second largest soybean producer in the world, with great prospects of being the largest producer (Lima et al, 2019). In Iran, 36 parasitoids have been reported to be associated with immature forms of H. armigera, with natural biological control levels ranging from 5 to 80%, depending on the crop and the stage of development in which the pest is found (Fathipour & Sedaratian, 2013). In Brazil, the natural occurrence in H. armigera caterpillars of Archytas marmoratus (Townsend, 1915) (Diptera: Tachinidae) (Guerra et al, 2014) and Campoletis sonorensis (Cameron, 1886) (Hymenoptera: Ichneumonidae), A. incertus (Macquart, 1851) (Diptera: Tachinidae) parasitoids has been recorded, associated with H. armigera, in which the larval parasitism rate was higher than 41% in areas of structured cotton refuge, without the use of chemical insecticides (Luz et al, 2018)

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