Foraging activity of Palmistichus elaeisis (Hymenoptera: Eulophidae) at various densities on pupae of the eucalyptus defoliator Thyrinteina arnobia (Lepidoptera: Geometridae)
Keywords:
biological control, looper of eucalyptus, parasitism, pupal parasitoidAbstract
Parasitoids are the main component of biological control of Lepidoptera defoliators in forested areas, and the densities of host insects can affect the efficiency of these natural enemies. The aim of this work was to study the biology and parasitism of Palmistichus elaeisis Delvare & LaSalle (Hymenoptera: Eulophidae) at various densities of females on individual pupae of Thyrinteina arnobia Stoll (Lepidoptera: Geometridae), the major Lepidoptera pest in eucalyptus (Myrtaceae) plantations in Brazil. Thyrinteina arnobia pupae were exposed to P. elaeisis females at various parasitoid-to-host ratios: (1:1, 3:1, 6:1, 9:1, 12:1, 15:1, 18:1, and 21:1), with 12 replications. The parasitism (81.8%) and emergence (100%) rates of P. elaeisis on T. arnobia pupae were highest with 15 ovipositing females per host. The life cycle (egg to adult) of P. elaeisis was shortest (19.8 ± 0.5 d) at a ratio of 21:1. The largest production of P. elaeisis per T. arnobia pupa was obtained at the ratios of 15:1 (298.4 ± 5.0) and 18:1 (287.4 ± 4.3). The female sex ratio of parasitoid offspring was highest (0.97 ± 0.01) with a parasitoid-to-host ratio of 12:1. The density of 15 P. elaeisis females per T. arnobia pupa was the most appropriate one for providing high parasitism (81.8%), emergence (100%), and progeny (298.4 ± 5.0) of this parasitoid.
Resumo
Parasitoides são os principais componentes de controle biológico de lagartas desfolhadoras em áreas florestais e o número de fêmeas por hospedeiro pode afetar a eficiência desses inimigos naturais. O objetivo deste trabalho foi estudar a biologia e o parasitismo de Palmistichus elaeisis Delvare e LaSalle (Hymenoptera: Eulophidae) em diferentes densidades de fêmeas desse parasitoide por pupa de Thyrinteina arnobia Stoll (Lepidoptera: Geometridae), principal lepidóptero-praga em plantações de eucalipto no Brasil. Pupas de T. arnobia foram expostas ao parasitismo por fêmeas P. elaeisis nas seguinte proporções de parasitoides/hospedeiro: 1:1, 3:1, 6:1, 9:1, 12:1, 15:1, 18:1 e 21 :1, com 12 repetições. O parasitismo (81,8%) e emergência (100%) de P. elaeisis em pupas de T. arnobia foram maiores com 15:1 parasitoides/hospedeiro. O ciclo de vida (ovo-adulto) de P. elaeisis foi mais curto (19,8 ± 0,5 dias) em uma proporção de 21:1. A maior produção de P. elaeisis por pupa de T. arnobia foram obtidas nas densidades de 15:1 (298,4 ± 5,0) e 18:1 (287,4 ± 4,3), respectivamente. A razão sexual do parasitoide foi maior (0,97 ± 0,01), com 12:1. A densidade de 15 P. elaeisis fêmeas por pupa de T. arnobia foi o mais adequado por apresentar maior parasitismo (81,8%), emergência (100%) e progênie (298,4 ± 5,0) do parasitoide.
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