Capacidade reprodutiva de Podisus nigrispinus (Heteroptera: Pentatomidae) com diferentes freqüências de acasalamento e troca de parceiros em plantas de soja

• Autor(a) principal: Soares, Marcus Alvarenga
• Data de Publicação: 2006
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/4587
• topic: Soja; Controle biológico; Podisus nigrispinus; Soybean; Biological Control; Podisus nigrispinus; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOTECNIA

The soy, Glycine max (L.) Merrill, is the most important export culture for many countries such as the United States, Argentina and Brazil. Its cultivation in extensive monocultures can increase the risk of pests including defoliating caterpillars and the biological control with predators represent an important tool in the integrated pest management of them. Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) is the most studied Pentatomidae predator for this crop. The objective of this research was to study the reproductive characteristics, the parameters of the fertility an life expectancy tables and morphological changes of the espermateca of P. nigrispinus with different mating frequencies and change of males on soy plants of the Conquest cultivar. The treatments were: T1- one mating period- pairs of P. nigrispinus were maintained together during five days and separated definitively; T2- changing males- males of this predator was changed every five days randomly during the whole life of the female; T3- intermittent periods of mating- males of P. nigrispinus were separately from the females during periods of ten days every five days during the whole life of the females; T4- continuous contact- males and females of P. nigrispinus were maintained together during their whole life. The pairs of P. nigrispinus received water, daily, and four pupae of T. molitor twice a week. The number of eggs per female of P. nigrispinus was similar between treatments with 520.81 ± 77.33, 509.00 ± 61.10, 615.81 ± 90.54 and 496.87 ± 35.37 eggs in the T1, T2, T3 and T4, respectively but that of the nymphs was lower in the T1 with 256.12 ± 54.58. The survival of females of P. nigrispinus was lower in the treatments T2 and T4 and the liquid reproductive rate (Ro) smaller in the T1 with 115.34 ± 15.65 females produced per female of this predator. The other treatments had values of Ro similar with 184.86 ± 23.04, 209.27 ± 28.91 and 182.03 ± 27.01 females produced, respectively in the T2, T3 and T4. The intrinsic growth rate (rm) and the finite reason of increase (λ) were lower in the treatment T1 and the maximum reproductive value (VRx) of P. nigrispinus was 40.44, 32.76, 48.09 and 35.14 females per female in the treatments T1, T2, T3 and T4 respectively. A single mating period was not enough to maintain the egg viability of P. nigrispinus. The smallest values of Ro, and rm in the T1 reinforce the fact that females of this predator do not maintain its fertility, only, with a mating period. The espermateca of P. nigrispinus females does not present a volume sufficient to store enough spermatozoids for their whole life. The espermateca is of round shape with great amount of spermatozoids and secretions in its interior after the mating. However, this organ becomes prolonged and empty with folds in its epiderm along the lifetime of females of this predator due to the depletion of spermatozoids. On the other hand, the periods between mating are beneficial to maintain the number and the appropriate viability of eggs and to increase the survival of P. nigrispinus females. The highest peak of specific fertility (mx) and the reproductive value (VRx) in the T3 than in the T2 and T4 shows that repeated mating followed by periods of absence of males can stimulate the fertility of P. nigrispinus.