Browsing by Author "Ahumada Becker, María Isabel"

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    Biogeographical Patterns of Herbivore Arthropods Associated with Chenopodium quinoa Grown along the Latitudinal Gradient of Chile
    (2021) Chorbadjian Alonso, Rodrigo Armen; Ahumada Becker, María Isabel; Urra, Francisco; Elgueta, Mario; Gilligan, Todd M.
    Identifying the particular guilds of herbivore arthropods that affect the production of crops is key to developing sustainable pest-management strategies; however, there is incomplete information about the identity of herbivore arthropods that could potentially damage the production of both highland and lowland quinoa landraces grown in Chile. By both reviewing the literature and conducting field collections across a large latitudinal gradient, we generated an updated list of 43 herbivore arthropods associated with quinoa production in Chile. In general, most species are polyphagous feeders, and only seven are specialists. The number and identity of species varied in relation with the latitude, such that four distinctive assemblages of herbivores were identified, each containing 32, 27, 34, and 22 species between latitudes 18-26, 26-32, 32-40, and 40-44 degrees S, respectively. The most northern production area (18-26 degrees S) is affected by nine unique species, including the major quinoa pest Eurysacca quinoae PovolnATIN SMALL LETTER Y WITH ACUTE (Lepidoptera: Gelechiidae). Similarly, the central area (32-40 degrees S) contains four unique species, including Eurysacca media PovolnATIN SMALL LETTER Y WITH ACUTE (Lepidoptera: Gelechiidae) and Orthotylus flavosparsus (Sahlberg) (Hemiptera: Miridae). The particular species assemblages described here will help further development of local pest-management practices.
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    Efectos de la defoliación causada por insectos mordedores (Trichoplusia ni) y de forma mecánica sobre parámetros cuantitativos y cualitativos del grano de quínoa (Chenopodium quinoa).
    (2019) Ahumada Becker, María Isabel; Chorbadjian Alonso, Rodrigo Armen; Pontificia Universidad Católica de Chile. Facultad de Agronomía e Ingeniería Forestal
    Los insectos pueden provocar daño en las plantas disminuyendo su crecimiento y producción afectando el rendimiento. Sin embargo, las plantas pueden compensar el daño, concepto denominado tolerancia. Referente a esto, no ha sido estudiada la respuesta a la defoliación sobre la cantidad y calidad del grano de la quínoa (Chenopodium quinoa Willd.) El objetivo de este trabajo fue evaluar el efecto del daño foliar, causado por insectos y de forma artificial en tres intensidades de daño sobre parámetros cuantitativos y cualitativos de los granos de quínoa. Las plantas fueron sometidas a diferentes intensidades de defoliación (20, 40 y 60%) producidas por larvas de gusano medidor del repollo (Trichoplusia ni Hübner) y de forma artificial. Se observó que la quínoa es capaz de tolerar hasta un 60% de defoliación produciendo el mismo rendimiento, biomasa, índice de cosecha y altura que plantas sin defoliar. Incluso con un nivel de defoliación de 20% tiende a sobrecompensar. Plantas defoliadas artificialmente presentaron menor cantidad de ramificaciones y menor cantidad de área foliar que las defoliadas por insecto y que las sin defoliar. Respecto a los aspectos cualitativos, no hubo diferencias entre el número, peso y peso de 1000 granos separados en diferentes calibres. En la composición química de los granos no hubo efecto sobre el contenido de fenoles ni la capacidad antioxidante. En el caso de las sapogeninas, la defoliación afectó su concentración, pero solo con la defoliación mecánica. Este es el primer estudio de tolerancia a la defoliación con distintos niveles mediante insectos mordedores y mecánicamente en plantas de quínoa.
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    Laboratory assays of the insecticidal activity of cyantraniliprole and imidacloprid on Brevicoryne brassicae, Myzus persicae (Hemiptera: Aphididae) and Trialeurodes vaporariorum (Hemiptera: Aleyrodidae) pests species and a biological control agent Chrysoperla defreitasi (Neuroptera: Chrysopidae)
    (2019) Ahumada Becker, María Isabel; Chorbadjian Alonso, Rodrigo Armen
    Cyantraniliprole has a broader insecticidal spectrum than the previously developed diamides. Because cyantraniliprole also targets hemipteran pests, it could provide an alternative to neonicotinoids like imidacloprid. However, there is limited information concerning how its broad-spectrum activity affects biological control agents. Toxicity of cyantraniliprole and imidacloprid to green peach aphid (Myzus persicae [Sulzer, 1776]), cabbage aphid (Brevicoryne brassicae [Linnaeus, 1758]) and greenhouse whitefly (Trialeurodes vaporariorum [Westwood, 1856]) nymphs was determined using both systemic and direct spray exposure. In addition, the direct spray activity of cyantraniliprole and imidacloprid on larvae of green lacewing, Chrysoperla defreitasi Brooks, 1994, was studied. Estimated LC50 values indicated that M. persicae, B. brassicae and T. vaporariorum were more susceptible to the systemic exposure to cyantraniliprole than to direct spray (0.148 vs. 24.284, 0.004 vs. 11.004, and 0.268 vs. 30.832 mg L-1, respectively). Similarly, susceptibility of M. persicae, B. brassicae and T. vaporariorum to imidacloprid was more pronounced when exposed systemically than through direct contact (0.018 vs. 1.149, 0.006 vs. 0.514, and 0.249 vs. 6.419 mg L-1, respectively). Hence, the population of B. brassicae was 40-fold more susceptible to cyantraniliprole than M. persicae when exposed to its systemic activity, and 2.2-fold more susceptible to cyantraniliprole's direct spray activity than M. persicae. Interestingly, T. vaporariorum was less susceptible to the direct spray activities of cyantraniliprole compared to that of imidacloprid by 4.8-fold, but both insecticides were equally toxic for this species after systemic exposure. Crysoperla larvae were less susceptible to direct exposure to cyantranaliprole in comparison with imidacloprid (640.295 vs. 26.974 mg L-1). In comparison to imidacloprid, direct spray insecticidal activity of cyantraniliprole was less toxic to these hemipteran pests and to chrysoperla larvae. This suggests that the selectivity of cyantraniliprole towards C. defreitasi, as measured by direct spray only, could decline if its concentration is increased to target these hemipteran pests by foliar sprays.