Quantifying the harmful potential of ten essential oils on immature Trichogramma pretiosum stages.

The use of chemical insecticides and non-selective natural products authorized for use in organic farming may reduce the effectiveness of egg parasitoids. The side-effects of ten plant essential oils on immature stages of Trichogramma pretiosum were evaluated. Carapa guianensis, Origanum vulgare and Zingiber officinalle during the F1 generation, and Azadirachtin and Mentha piperita in the F2 generation were slightly harmful (class II: 30-79%) to the emergence of this parasitoid. All essential oils affected the longevity of females of the F1 and F2 generations. Thymus vulgaris and Z. officinalle were the oils most harmful to female longevity. Carapa guianensis proved slightly harmful (class II: 30-79%) to parasitism in the F1 generation when applied during the egg-larval and pre-pupal stages and O. vulgare in the F1 generation in the pre-pupal stage alone, of this parasitoid. The sex ratio was lower than 0.5 during the pre-pupal stage of the F1 generation with Azadirachtin, C. guianensis, O. vulgare, Piper nigrum and Syzigium aromaticum, but this parameter was not affected for the other biological stages of T. pretiosum in the F1 and F2 generations. The Azadirachtin, C. guianensis, M. piperita, O. vulgare, T. vulgaris and Z. officinalle oils revealed a mild toxic effect to the immature stages of T. pretiosum and, therefore, it should be used according to patterns of ecological selectivity. Allium sativum and Citrus sinensis essential oils were not harmful to T. pretiosum, and can be used in Integrated Pest Management.

Can the Understory Affect the Hymenoptera Parasitoids in a Eucalyptus Plantation?

The understory in forest plantations can increase richness and diversity of natural enemies due to greater plant species richness. The objective of this study was to test the hypothesis that the presence of the understory and climatic season in the region (wet or dry) can increase the richness and abundance of Hymenoptera parasitoids in Eucalyptus plantations, in the municipality of Belo Oriente, Minas Gerais State, Brazil. In each eucalyptus cultivation (five areas of cultivation) ten Malaise traps were installed, five with the understory and five without it. A total of 9,639 individuals from 30 families of the Hymenoptera parasitoids were collected, with Mymaridae, Scelionidae, Encyrtidae and Braconidae being the most collected ones with 4,934, 1,212, 619 and 612 individuals, respectively. The eucalyptus stands with and without the understory showed percentage of individuals 45.65% and 54.35% collected, respectively. The understory did not represent a positive effect on the overall abundance of the individuals Hymenoptera in the E. grandis stands, but rather exerted a positive effect on the specific families of the parasitoids of this order.

Degeneration and cell regeneration in the midgut of Podisus nigrispinus (Heteroptera: Pentatomidae) during post-embryonic development.

Cell death, proliferation, and differentiation in some developmental stages of insects have been studied in the midgut of ametabolous, which undergo only continuous growth, and holometabolous, which undergo complete metamorphosis. However, in hemimetabolous insects, evolutionarily intermediate between ametabolous and holometabolous, midgut reorganization during the post-embryonic development has been poorly studied. The present study evaluates the post-embryonic development of the midgut of a hemimetabolous insect, Podisus nigrispinus, to test the hypothesis that these insects have programmed cell death and proliferation followed by differentiation of regenerative cells during midgut growth from nymphs to adult. The morphometrical data showed a 6-fold increase in midgut length from the first instar nymph to the adult, which did not result from an increase in the size of the midgut cells, suggesting that the growth of the midgut occurs by an increase in cell number. Cell death was rarely found in the midgut, whereas proliferation of regenerative cells occurred quite frequently. The growth of the midgut of P. nigrispinus appears to result from the proliferation of regenerative cells present in the epithelium; unlike ametabolous and holometabolous insects, the midgut of P. nigrispinus does not undergo extensive remodeling, as shown by the low frequency of digestive cell death.

Predation rate of Spodoptera frugiperda (Lepidoptera: Noctuidae) larvae with and without defense by Podisus nigrispinus (Heteroptera: Pentatomidae)

The effect of the defense of the prey Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) on predation rates of Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) females was studied. P. nigrispinus preyed 1.0, 1.4, 1.2, 3.8 and 3.0 and 0.4, 0.8, 1.6, 2.8 and 3.2 third instars of S. frugiperda larvae with and without defense, respectively, with the densities of one, two, four, six and eight larvae. The attack rate and the manipulation time were, respectively, 0.67 ± 0.39-h and 6.72 ± 2.88 h for P. nigrispinus females fed with larvae with defense and 2.51 ± 0.16-h and 0.51 ± 0.77 h for those without defense. The functional response of the predator P. nigrispinus varies with the defense and the density of the prey S. frugiperda, with larger consumption of prey without defense at higher densities.

Objetivou-se determinar o efeito da defesa da presa Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) na taxa de predação por fêmeas de Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae). Podisus nigrispinus, predou 1,0; 1,4; 1,2; 3,8; 3,0 lagartas de terceiro estádio de S. frugiperda com defesa, respectivamente, nas densidades de uma, duas, quatro, seis e oito lagartas, enquanto esses valores foram de 0,4; 0,8; 1,6; 2,8; 3,2 lagartas sem defesa, respectivamente, nessas densidades. A taxa de ataque (a) e o tempo de manipulação (Th) foram, respectivamente, de 0,67 ± 0,39-h e 6,72 ± 2,88 horas para fêmeas de P. nigrispinus alimentadas com lagartas com defesa e de 2,51 ± 0,16-h e 0,51 ± 0,77 horas para aquelas sem defesa. A resposta funcional do predador P. nigrispinus varia com a defesa e a densidade da presa S. frugiperda, com maior consumo de presas sem defesa em altas densidades.

Morphology of female reproductive tract of the predator Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) fed on different diets

Este estudo apresenta a morfologia do sistema reprodutor feminino de Podisus nigrispinus (Dallas) alimentado com larvas de Alabama argillacea (Hübner), Musca domestica L. e de Tenebrio molitor L. ou dieta artificial. As gônadas internas desse predador apresentaram coloração amarelada e, independente da dieta, cada ovário apresentou sete ovaríolos unidos pelos filamentos terminais em uma estrutura em forma de cacho. A análise histológica revelou que o ovário de P. nigrispinus é do tipo meroístico telotrófico com cada ovaríolo dividido morfologicamente em filamento terminal, trofário (câmara nutridora), vitelário e pedicelo. A dieta recebida por esse predador alterou o desenvolvimento e a morfometria de seus ovários. Fêmeas de P. nigrispinus alimentadas com larvas de terceiro ou quinto estádio de A. argillacea apresentaram ovários desenvolvidos com grande número de ovócitos em estágio avançado de desenvolvimento nos ovaríolos. Fêmeas com dieta artificial apresentaram ovários atrofiados e ovaríolos, praticamente, sem ovócitos em seu interior enquanto aquelas alimentadas com larvas de T. molitor ou M. domestica tiveram ovários em estágios intermediários de desenvolvimento. O comprimento do ovaríolo central foi maior em fêmeas alimentadas com larvas de quinto estádio de A. argillacea e menor naquelas com dieta artificial. Ovócitos em estágios mais avançados de desenvolvimento foram observados para fêmeas alimentadas com larvas de terceiro ou quinto estádios de A. argillacea, enquanto ovócitos atrofiados foram observados para aquelas com dieta artificial.