BRS Tapaihum and BRS Acauã cultivars showed the lowest cumulative insect emergence and instantaneous rates of population growth, and the highest insect mortality, mainly when the grains were obtained from plants inoculated with rhizobial strains. © 2016 Society of Chemical Industry.
-The objective of this work was to determine the biological parameters and thermal requirements of Trichogramma pretiosum TM strain reared on Helicoverpa armigera eggs. A card containing 20 eggs of H. armigera was offered for each T. pretiosum female, at temperatures of 18, 20, 22, 25, 28, 30 and 32°C. All life stages of T. pretiosum were observed under the given temperature conditions. The optimum temperature for the parasitism of T. pretiosum was 25°C, and the highest longevity was found at the same temperature. The highest parasitoid emergence rates occurred at temperatures of 22, 25 and 28°C. The highest proportion of T. pretiosum individuals emerged per egg was observed at 18°C. Concerning the sex ratio, the highest proportion of females occurred at 28°C, and the highest percentage of parasitism viability was observed at this same temperature. The lowest thermal threshold for total preimaginal development and thermal requirements of T. pretiosum were 10.82°C and 134.55 degree-days, respectively. The estimated number of generations of T. pretiosum in the average temperatures of municipality of Bom Jesus, state of Piauí, Brazil is four per month.Index terms: Trichogrammatidae, biological control, parasitoid, temperature. Parâmetros biológicos e exigências térmicas de Trichogramma pretiosum sobre ovos de Helicoverpa armigera Resumo -O objetivo deste trabalho foi determinar os parâmetros biológicos e as exigências térmicas deTrichogramma pretiosum linhagem TM sobre ovos de Helicoverpa armigera. Para cada fêmea, foi oferecida uma cartela contendo 20 ovos de H. armigera, às temperaturas de 18, 20, 22, 25, 28, 30 e 32°C. Todos os estádios de vida de T. pretiosum foram observados sob as dadas condições de temperatura. A temperatura ótima para o parasitismo de T. pretiosum foi de 25°C e a maior longevidade foi verificada à mesma temperatura. As maiores taxas de emergência do parasitoide foram às temperaturas de 22, 25 e 28°C. A maior proporção de indivíduos de T. pretiosum emergidos por ovo foi observada a 18°C. Quanto à razão sexual, a maior proporção de fêmeas ocorreu a 28°C, e o maior percentual de viabilidade do parasitismo foi observado à mesma temperatura. O limiar térmico inferior para o desenvolvimento pré-imaginal total e as exigências térmicas de T. pretiosum foram de 10,82°C e 134,55 grau-dias, respectivamente. O número estimado de gerações de T. pretiosum às temperaturas médias do Município de Bom Jesus, Piauí, foi de 4 por mês.Termos para indexação: Trichogrammatidae, controle biológico, parasitoide, temperatura.
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. Palavras-chave: Controle biológico, lagarta da soja, parasitoide de ovos.Parâmetros biológicos de três linhagens de Trichogramma pretiosum (Riley, 1879) (Hymenoptera: Trichogrammatidae) sobre ovos de Helicoverpa armigera (Hübner, 1805) (Lepidoptera: Noctuidae) RESUMO. Este trabalho teve como objetivo estudar os parâmetros biológicos de Trichogramma pretiosum em ovos de H. armigera. As três linhagens de T. pretiosum avaliadas foram: TM, TMC e TLEM, oriundas de diferentes localidades. O delineamento experimental foi inteiramente casualizado com vinte repetições por tratamento, sendo utilizada uma fêmea do parasitoide por repetição e posteriormente foram oferecidos 20 ovos de H. armigera. O experimento foi mantido em câmaras BOD a 25 ± 2° C, UR 60 ± 10% e fotofase de 14 horas. Avaliou-se os seguintes parâmetros biológicos: porcentagem de parasitismo, porcentagem de emergência, número de adultos emergidos por ovo, razão sexual, viabilidade, longevidade e duração do ciclo. A porcentagem de parasitismo e viabilidade e número de indivíduos por ovo foram superiores para as linhagens TM e TMC. A linhagem TMC apresentou a maior proporção para razão sexual, não diferindo estatisticamente da linhagem TM. A longevidade da linhagem TM se destacou em relação às demais. Não houve variação com relação a duração do ciclo. Assim de acordo com os parâmetros biológicos avaliados, conclui-se que Trichogramma pretiosum linhagem TM obteve o melhor desenvolvimento nos ovos de H. armigera em condições de laboratório.
This study aimed to assess the resistance of grain from two varieties of maize landraces in initial breeding in Bom Jesus-PI, with respect to S. zeamais attack. Seeds of two maize landraces were used: purple straw maize from two different origins (São Paulo (SP) and Espírito Santo (ES)) and Peruvian purple maize. The experimental design was completely randomized with four replications. The data for each response variable were subjected to analysis of variance, applying the F-test (p ≤ 0.05), and when significant differences were found, there was a comparison of means by Tukey test (p ≤ 0.05). The statistical analyses were performed using the software SAS ® . In a free-choice test and bioassay for evaluating the nutritional index (no choice test), maize varieties differed significantly by Tukey test and the cultivar SP was considered resistant, while the cultivars purple and ES were considered susceptible.
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