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Abstract The ages of parasitoid females and their hosts can have substantial effects on parasitism and parasitoid efficacy. This relationship has been investigated over the last few decades and found to vary among species. To our knowledge, it was virtually unknown for Trichogramma pretiosum wasps that parasitize Anticarsia gemmatalis eggs. Therefore, the influence of parasitoid and host age on the parasitism of T. pretiosum on eggs of A. gemmatalis was here evaluated in three independent bioassays. Neither the number of parasitized eggs nor that of emerged parasitoids differed between T. pretiosum females of different age. The number of parasitoids per egg and the sex ratio were higher for 5-day-old females. Regarding host age, the number of parasitized eggs was highest for A. gemmatalis eggs aged 24 h (9.60), followed by eggs aged 48 h (1.00), while no parasitism was observed for eggs aged 72 h. The number of parasitoids per egg and sex ratio were not influenced by host age. Preference was significantly higher for host eggs aged 24 h (79.67%), followed by eggs aged 48 h (16.99%) and 72 h (3.33%). Accordingly to these results, the key challenge for a successful T. pretiosum release to control A. gemmatalis in the field is to synchronize the presence of up to 5-day-old adults with the most susceptible phase of the host eggs (1 day).
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ABSTRACT: The objective of this study was to evaluate extent of larval period, larval survival (%), food consumption, and pupal biomass of Spodoptera eridania and Spodoptera frugiperda (Lepidoptera: Noctuidae ) fed on fresh ears of field corn expressing Bt proteins (Cry1F and Cry1F+Cry1A.105+Cry2Ab2). Larvae of Spodoptera spp. survived less than two days when they consumed Bt corncobs and showed 100% mortality. Spodoptera eridania reared on non-Bt corn cobs showed higher larval development (21.6 days) than S. frugiperda (18.4 days) and lower viability (56.4% and 80.2% for S. eridania and S. frugiperda , respectively). A higher amount of corn grains was consumed by S. eridania (5.4g) than by S. frugiperda (3.9g). In summary, this study demonstrated that the toxins Cry1F and Cry1F + Cry1A.105 + Cry2Ab2 expressed in fresh corn cobs contributed to protect ears of corn against S. frugiperda and the non-target pest S. eridania . However, itis important to monitor non-Bt cornfields because of the potential of both species to cause damage to ear sof corn.
RESUMO: Este estudo teve como objetivo avaliar o período de desenvolvimento larval, sobrevivência larval (%), consumo de alimento e biomassa pupalde Spodoptera eridania e Spodoptera frugiperda (Lepidoptera: Noctuidae ), alimentadas com grãos verdes de milho Bt que expressam as proteínas Cry1F e Cry1F + Cry1A.105 + Cry2Ab2). As larvas de Spodoptera spp. alimentadas com milho Bt sobreviveram por até dois dias, registrando-se 100% de mortalidade. A espécie S. eridania alimentada com grãos de milho não Bt apresentou um maior desenvolvimento larval (21,6 dias) do que S. frugiperda (18,4 dias), e menor viabilidade larval (56,4% e 80,2% para S. eridania e S. frugiperda respectivamente). Uma maior taxa de consumo de grãos foi observada para S. eridania (5,4g) do que para S. frugiperda (3,9g). Em síntese, este estudo comprova que as toxinas Cry1F e Cry1F + Cry1A.105 Cry2Ab2 expressas em grãos imaturos de milho contribuem na proteção das espigas de milho contra S. frugiperda e a praga não-alvo S. eridania , entretanto, é importante monitorar as lavouras cultivadas com milho não Bt, devido o potencial de ambas as espécies em ocasionar danos nas espigas da planta.
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ABSTRACT This study aimed to evaluate the development and reproduction of the black armyworm, Spodoptera cosmioides when larvae fed on leaves of Bt-corn hybrids, expressing a single Cry1F and also Cry1F, Cry1A.105 and Cry2Ab2 in pyramided corn and their non-Bt-isoline (hybrid 2B688), as well as on leaves of two soybean isolines expressing the Cry1Ac protein and its non-Bt isoline (A5547-227). We also assessed the effect of these Bt and non-Bt plants on the leaf consumption rate of S. cosmioides larvae. This pest was unable to develop when fed on any of the corn isolines (Bt and non-Bt). When both 1st and 3rd instar larvae were fed on corn leaf, mortality was 100% in both Bt and non-Bt corn. In contrast, when corn leaves were offered to 5th instar larvae, there were survivors. Defoliation and leaf consumption was higher with non-Bt corn than with both of the Bt corn isolines. There was no negative effect of Bt soybean leaves on the development and reproduction of S. cosmioides with respect to all evaluated parameters. Our study indicates that both Bt and non-Bt corn adversely affect the development of S. cosmioides while Bt soybean did not affect its biology, suggesting that this lepidopteran has major potential to become an important pest in Bt soybean crops.
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RESUMO: Este estudo investigou os aspectos biológicos de Dichelops melacanthus (Hemiptera: Pentatomidae) em três temperaturas (19±1°C, 25±1°C e 31±1°C), alimentados com grãos imaturos de milho 2B688Hx (expressa a proteína inseticida Cry1F, para o controle de lepidópteros-alvo) e 2B688. Foi observado que a temperatura de 19±1°C prejudicou o desenvolvimento de D. melacanthus, pois, nessa condição, foi registrada a maior taxa de mortalidade das ninfas, menor peso de adultos e as fêmeas não ovipositaram. Por outro lado, a duração da fase jovem, mortalidade, peso de adultos, fecundidade e viabilidade de ovos não diferiu entre as temperaturas 25±1°C e 31±1°C. Também foi demonstrado que os aspectos biológicos dos percevejos alimentados com grãos imaturos de milho 2B688Hx não diferiram dos que se desenvolveram com a isolinha 2B688. Este estudo comprova que D. melacanthus desenvolve-se melhor em condições de temperaturas mais elevadas (até 31±1°C), e o fato de se alimentar com grãos imaturos de milho 2B688Hx não afeta o seu desenvolvimento.
ABSTRACT: This study investigated the development of Dichelops melacanthus (Hemiptera: Pentatomidae) at different temperatures (19±1°C, 25±1°C and 31±1°C) reared on 2B688Hx (expressing Cry1F insectice protein to control lepidopterans target) immature corn grains. The temperature of 19±1°C impaired the development of D. melacanthus and recorded the highest mortality of nymphs, lower weight and adult females laid no eggs. Moreover, the length of the nymphal biology, adult weight, fecundity and viability of eggs did not differ between temperatures 25±1°C and 31±1°C. It was also shown that the biological aspects of green belly stink bugs fed with 2B688Hx immature grains of corn do not differ from that develop with 2B688 isoline. This study showed that the biological cycle of D. melacanthus is favored at warmer temperature (until 31±1°C), and the consume of immature corn grain 2B688Hx does not affect its development.
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This study aimed to evaluate, in controlled laboratory conditions (temperature of 25±2 °C, relative humidity of 60±10%, and 14/10 h L/D photoperiod), the larval development of Spodoptera eridania (Cramer, 1784) (Lepidoptera, Noctuidae) fed with leaves of Bt maize expressing Cry1F and Cry1F + Cry1A.105 + Cry2Ab2 insecticide proteins and its non-Bt isoline. Maize leaves triggered 100% of mortality on S. eridania larvae independently of being Bt or non-Bt plants. However, it was observed that in overall Bt maize (expressing a single or pyramided protein) slightly affects the larval development of S. eridania, even under reduced leaf consumption. Therefore, these results showed that Cry1F and Cry1F + Cry1A.105 + Cry2Ab2 can affect the larval development of S. eridania, although it is not a target pest of this plant; however, more research is needed to better understand this evidence. Finally, this study confirms that non-Bt maize leaves are unsuitable food source to S. eridania larvae, suggesting that they are not a potential pest in maize fields.
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Introduction: There is a consensus that dentine/resin bonding deteriorates over time, and such degradation is one of the main reasons for limiting adhesive restoration longevity. Enzymes known as matrix metalloproteinases (MMPs) are responsible by enzymatic degradation of collagen fibrils without protection, which are present in the resin-dentine interface. Therefore, these enzymes are involved in the process of adhesive interface degradation. Currently, studies point out chlorhexidine digluconate has antiproteolytic function by inhibiting the action of MMPS. Thus, it is thought this substance application prior to the use of bonding agents could slow the process of degradation of the tooth-restoration interface, resulting in longevity. Objective: To review the literature on the influence of chlorhexidine application on the stability of the adhesive interface. Literature review: Chlorhexidine digluconate proprieties and its application in Dentistry were discussed. Next, hybrid layer formation and degradation was discussed and the mechanism of action of chlorhexidine on preserving this layer was detailed. Finally, scientific studies from the last six years were analyzed on the performance of adhesive systems after chlorhexidine application. Results: Considering the results of reviewed studies, it can be concluded that chlorhexidine application did not interfere on the immediate bond strength to dentin and hybrid layer degradation over time occurred later and/or with lower intensity. Conclusion: Chlorhexidine application interferes positively when incorporated into the adhesion protocols, by promoting hybrid layer stability over time.
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No impact of Bt soybean that express Cry1Ac protein on biological traits of Euschistus heros (Hemiptera, Pentatomidae) and its egg parasitoid Telenomus podisi (Hymenoptera, Platygastridae). Biological traits of the stink bug Euschistus heros and its main biological control agent Telenomus podisi were evaluated under controlled environmental conditions (25 ± 2ºC; 60 ± 10% RH; and 14/10 h photoperiod) by placing first instar nymphs into Petri dishes with pods originating from two soybean isolines (Bt-soybean MON 87701 × MON 89788, which expresses the Cry1Ac protein, and its near non-Bt isoline A5547) where they remained until the adult stage. Due to gregarious behavior exhibited by first instar nymphs, they were individualized only when at the second instar. Adults were separated by sex and weighed, and pronotum width of each individual was subsequently measured. They were placed into plastic boxes containing soybean grains of the same soybean isoline as food source. Egg viability and female fecundity were assessed in adult individuals. Adult females of T. podisi (up to 24h old) were placed with eggs of E. heros from mothers reared on both soybean isolines. Nymphal development time, insect weight, pronotum width, sex ratio, female fecundity, and egg viability (% emergence) of Euschistus heros did not differ between treatments. Eggto-adult development time, female longevity, sex ratio, and percentage of parasitized eggs were not impacted by the Bt-soybean (expressing Cry1Ac protein). Results indicate that the Bt-soybean, MON 87701 × MON 89788, has no direct significant impact on the two studied species.
