Abstract
This project has an objective to study the biological parameters of Trichogramma pretiosum on eggs of H. armigera . The three strains of T. pretiosum were evaluated: TM, TMC and TLEM, from different places. The experimental establishing was completely randomizing with twenty repeats per treatment, being used by a female parasitoid by repetition and later on they were offered 20 H. armigera eggs. The experiment was kept on BOD cameras to 25 ± 2° C, UR 60 ± 10% and photo phase of 14 hours. Evaluating the following biological parameters: parasitism percentage, emergency percentage, number of adults emerged per egg, sex ratio, viability, and longevity and cycle duration. The parasitism percentage, viability and number of individuals per egg were higher for TM and TMC. The TMC strain presented a larger sex ratio proportion, not being different statistically from the TM stream. The longevity of the strain TM was different regarding the others. There was no variation regarding the cycle duration. Therefore, according with the evaluated biologic parameters, it is concluded that Trichogramma pretiosum strain TM obtained a better egg development of H. armigera on laboratory conditions.
Highlights
Among the insect pests that are able to limit the production of soybean, we emphasize the (Hemiptera: Pentatomidae) bugs and the complex of defoliating caterpillars. This situation has worsened with the recording of the occurrence of Helicoverpa armigera (Hübner, 1805) (Lepidoptera: Noctuidae) in Brazil (Czepak, Albernaz, Vivan, Guimarães, & Carvalhais, 2013; Tay et al, 2013; Gómez et al, 2016), where it was classified as an A1 quarantine pest and it is currently found in the states of Goiás, Bahia, Mato Grosso and Piauí mainly associated to soybean, cotton and tomato crops (Czepak et al, 2013; Gómez et al, 2016)
We evaluated the following biological parameters of T. pretiosum: parasitism percentage by counting the darkened eggs; emergence percentage, emergence percentage by counting of adults; viability percentage acquired by counting the host eggs that had outlet orifice of the adults viewed under a stereoscopic microscope; number of adults emerged per egg calculated using the formula: No of females + No of males
We observed differences in the aggressiveness of the strains evaluated on the H. armigera eggs being TM and TMC the superior strains in relation to TLEM, respectively (Figure 1A)
Summary
Among the insect pests that are able to limit the production of soybean, we emphasize the (Hemiptera: Pentatomidae) bugs and the complex of defoliating caterpillars This situation has worsened with the recording of the occurrence of Helicoverpa armigera (Hübner, 1805) (Lepidoptera: Noctuidae) in Brazil (Czepak, Albernaz, Vivan, Guimarães, & Carvalhais, 2013; Tay et al, 2013; Gómez et al, 2016), where it was classified as an A1 quarantine pest and it is currently found in the states of Goiás, Bahia, Mato Grosso and Piauí mainly associated to soybean, cotton and tomato crops (Czepak et al, 2013; Gómez et al, 2016). Such knowledge enables selecting strains that are well adapted to the pest to be controlled (Bezerra & Parra, 2004)
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