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ABSTRACT This study aims to report the occurrence of Heilipus draco in seeds of Ocotea puberula, and to describe the main injuries caused to the seeds and the effects on germination, as well as the occurrence of parasitoid hymenopterans. To this end, fruits of seven trees were selected, in the extreme south of the Atlantic Forest, Brazil. Fruit collection was carried out weekly in the middle third of the canopy, forming lots, from the beginning of fruit formation until total dehiscence, for two years. In order to examine the damage caused by the granivorous insects inside the fruits, 100 fruits were sectioned taking into account the batch/year with the aid of a scalpel and analyzed using a binocular stereomicroscope. In the same way, 144 fruits from each lot/year were stored individually in transparent plates in order to verify the occurrence and identification of species of granivorous insects. The proof of the influence of the injury caused to the seeds by the granivorous insects was carried out by the germination test, with four replications of 25 seeds, comparing seeds with and without oviposition holes. The species H. draco was found to be associated with the fruits of O. puberula. The egg-layings are endophytic, carried out directly on the seed. Larval parasitism of Hymenoptera Bracon, Omeganastatus, Scambus and Triapsis was observed. It is concluded that the cycle from egg to adult takes place inside the seed of O. puberula, and the injuries caused by the larvae decrease germination.
ABSTRACT
ABSTRACT Forest species can have their seeds damaged by granivorous insects, especially by those in their larval stage. In this context, this study aims to report the occurrence of Amblycerus species in Cordia trichotoma seeds, to describe their main damage to seeds and effects on germination, as well as their associated hymenopteran parasitoids. Therefore, seven trees were selected in the municipality of Taquaruçu do Sul, RS, Brazil. Fruits were collected weekly from the medium third of the tree crown, from the beginning of their formation until total dehiscence. To examine the damage caused by granivorous insects within the fruits, 15 fruits from each tree were sectioned with a scalpel. Furthermore, 10 fruits from each tree were stored individually in clear plates to verify the occurrence and identification of granivorous insect species. Evidence of the damage caused to seeds was verified through the germination test by comparing preserved and damaged seeds, with four repetitions of 25 seeds each. The species Amblycerus longesuturalis and Amblycerus profaupar (Chrysomelidae: Bruchinae) were found associated with fruits of C. trichotoma. Female insects predominantly laid eggs on the superior part between the marcescent calyx and the fruit, and larvae perforated the fruit tegument to start consuming seed embryos and reserves. Bruquine larvae are parasitized by Hymenoptera of Bracon, Mirax, Omeganastatus and Triapsis genera. In conclusion, the germination of C. trichotoma seeds is significantly affected by emergence orifices caused by granivorous species.
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ABSTRACT The cultivation of genetically modified crops in Brazil has led to the need to assess the impacts of this technology on non-target species. Under field conditions, the potential effect on insect biodiversity was evaluated by comparing a homogeneous corn field with conventional and transgenic maize, expressing different Bt proteins in seven counties of Minas Gerais, Brazil. The richness pattern of non-target insect species, secondary pests and natural enemies were observed. The results do not support the hypothesis that Bt protein affects insect biodiversity. The richness and diversity data of insects studied were dependent on the location and other factors, such as the use of insecticides, which may be a major factor where they are used.
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ABSTRACT: The effects of six diets on biological parameters of Euschistus heros (F.) (Heteroptera: Pentatomidae) and its susceptibility to entomopathogenic fungi Beauveria bassiana (Bb) and Metarhizium anisopliae (Ma) were studied. The diets included a standard diet (bean pods+soybeans, peanuts and sunflower) and diets in which the bean pods were combined with only one type of grain, either soybean, peanut, sunflower, pea or sesame seeds. The best performance was that of insects fed on standard diet, which had the shortest development period and 49.5% of egg-to-adult viability. The insects fed the pea diet exhibited less than 30% viability and 11% of adults had wing deformations. The finite rate of increase values for the treatment groups were: standard: 1.091; soybean: 1.077; peanut: 1.071; sunflower: 1.076; pea: 1.058; and sesame: 1.065. The susceptibility to Ma (55%) was greater than Bb (40%) only for insects fed on the sesame diet. Considering the effects of diet on susceptibility to both fungal species comparatively among the diet-treatment groups, the stink bugs fed the restrictive diets were more susceptible compared with those fed the standard diet. We concluded that diet composition affects the biological parameters of E. heros and differentially affects their susceptibility to Bb and Ma fungi.
ABSTRACT
Simplification of natural habitats leads to a modification of the community associated with a host plant. Pequi trees (Caryocar brasiliense) are common to find in central Brazil, especially in the middle of monocultures, such as soy, corn, pasturelands or Eucalyptus plantations. On this scenario we hypothesized that habitat modification differentially affects the diversity of ants and herbivore insects associated with this species. The aim of the work was to test if C. brasiliense trees located in human modified habitats, support a lower species richness and abundance of ants, and a greater species richness and abundance of insect herbivores, compared to preserved cerrado habitats. The study was conducted in a Cerrado area located in Northern Minas Gerais State, Brazil. Ants and herbivore insects were collected monthly during 2005 using beating technique. The results showed that ant species richness was higher in pequi trees located in preserved Cerrado, followed by trees in pastureland and Eucalyptus plantation, respectively. The ant abundance was lower in the Eucalyptus plantation but no difference in ant abundance was observed between trees in pastureland and the preserved Cerrado. Moreover, herbivore insects exhibited lower number of species and individuals in trees located in the preserved Cerrado than in the pastureland and Eucalyptus plantation. We concluded that habitats simplified by human activities may result in diversity loss and may change species interactions.
La simplificación de los hábitats naturales conduce a una modificación de la comunidad asociada con una planta huésped. En la región central de Brasil es muy común encontrar árboles aislados de “pequi” (Caryocar brasiliense) en medio de monocultivos de soya, maíz, pastos o plantaciones de eucalipto. Bajo este escenario, nosotros predecimos que la modificación del hábitat afecta diferencialmente la diversidad de hormigas y herbívoros asociados a árboles de “pequi”. El objetivo de este artículo fue determinar que árboles de “pequi” localizados en hábitats modificados por actividades humanas (i.e. pastizales y plantaciones de Eucalyptus), soportan una menor abundancia y riqueza de especies de hormigas. Por el contrario, se espera una mayor abundancia y riqueza de especies de herbívoros en hábitats modificados. Este estudio fue realizado en un área de Cerrado (sabana brasileña) localizado en el Norte del estado de Minas Gerais, Brasil. Las hormigas y los herbívoros fueron muestreados usando técnicas de golpe. La riqueza de especies de hormigas fue mayor en árboles de “pequi” localizados en áreas preservadas de Cerrado, seguida por árboles de pastizales y finalmente por árboles de plantaciones de Eucalyptus. La abundancia de hormigas fue menor en plantaciones de Eucalyptus, pero no hubo diferencias en la abundancia de hormigas entre árboles de pastizales y áreas preservadas de cerrado. Por otra parte, el número de especies de insectos herbívoros fue menor en árboles de áreas preservadas de Cerrado que en pastizales y plantaciones de Eucalyptus. Concluimos que las actividades humanas reducen la complejidad del hábitat resultando en la pérdida de la diversidad de insectos y procesos ecológicos.