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BACKGROUND: Transgenic Bt technology in soybean, with plants expressing Cry1Ac, has been adopted as an insect pest management tool. It was first adopted in large areas of South America and Asia in 2013. The risk of resistance in target pests to this technology demands insect resistance management (IRM) programs. In Brazil, a structured refuge (area of non-Bt soybean) planted adjacent to the Bt soybean crop has been an important IRM recommendation, particularly for the primary lepidopteran defoliators Anticarsia gemmatalis (Lepidoptera: Erebidae) and Chrysodeixis includens (Lepidoptera: Noctuidae). The overall goal of this study was to validate IRM recommendations to Bt soybean. The objectives were to document the impact of soybean phenology, cultivar choice and non-Bt soybean defoliation on moth oviposition. In addition, a mark-release-recapture study estimated the dispersal capacity of these species. Five field experiments per species were performed for 3 years. RESULTS: Our results revealed an increase in A. gemmatalis and C. includens oviposition, respectively, on Bt plants as a consequence of the difference in plant growth stage at the time of oviposition. Defoliation of non-Bt plants significantly increased the oviposition preference of both moth species for Bt plants. The mark-release-recapture experiment indicated an average dispersal distance of ~300 m from the release point for A. gemmatalis, with maximum recapture at 1000 m. CONCLUSION: Overall, our findings emphasize the importance of planting synchronization of Bt soybean and the structured refuge. In addition, when operational aspects in large soybean areas challenge this recommendation, the priority should be for planting the refuge area first. This approach will minimize the impact of selective oviposition of A. gemmatalis and C. includens. © 2024 Society of Chemical Industry.

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We studied the impact of field temperature on the emergence of Telenomus podisi Ashmead (Hymenoptera: Scelionidae) after being released as either protected (encapsulated) or unprotected pupae close to adult emergence. Two independent bioassays (protected pupae vs. unprotected pupae) were carried out in a randomized block experimental design in a 2 (parasitoid rearing temperature regimes) ×4 (release positions within plant canopy) factorial scheme. One of the T. podisi colonies was reared at a constant temperature (25 °C) and 12:12 h L:D (Light: Dark) photoperiod. The second T. podisi colony was reared at fluctuating temperatures (20 °C during 12 h D and 30 °C during 12 h of L). Each bioassay had five replicates. Each replicate contained 40 pupae from each rearing temperature and release position within plant canopy. Parasitoid pupae were released in the bottom third, middle third, or upper third of the plant's canopy, as well as between planting lines. Each bioassay was repeated six times (in different plant developmental stages: R1, R2, R3, R4, R5 and R6). There was no difference in emergence of parasitoids between colonies reared at different temperatures after exposure to field conditions. Emergence of T. podisi was reduced after pupae exposure to temperatures above 35 °C in the field, regardless of the rearing temperature. Telenomus podisi tolerates temperature fluctuations for emergence as long as they fit the optimal range (20 to 30 °C).

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BACKGROUND: The egg-parasitoid wasp Telenomus podisi has received attention as a biological-control agent for one of the most important soybean pests in Brazil, the stink bug Euschistus heros. As yet, no studies have conclusively established strategies for the release of T. podisi. We developed a computational model using cellular automata in the C programming language to investigate release strategies for T. podisi in soybean crops, in order to optimize the use of these wasps in managing E. heros, assuming a two-dimensional grid of cells corresponding to a soybean field. RESULTS: The release strategies capable of maintaining an E. heros population below the Economic Threshold level involved releasing a total of at least 15 000 female parasitoids per hectare, in three or four releases of 5000 or more (equivalent to approximately 7142 or more male and female parasitoids per hectare, assuming a sex ratio of 0.70). A 25-m spacing between release points or strips was indicated. The model is very sensitive to the variation in the number of parasitoids per release and in the number of releases, but little sensitive to the release mode and spacing values. CONCLUSION: The theoretical results produced by the computational model are expected to guide future field studies to improve T. podisi release plans for managing E. heros in soybeans. Therefore, we recommend the release strategy of three to four releases of 5000 or more female parasitoids per hectare, at points or strips spaced 25 m apart, to be tested in field experiments for proper implementation by producers. © 2022 Society of Chemical Industry.

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Environmental variables may markedly influence egg parasitoid performance and must be considered when choosing the best release strategy. Thus, this study aimed to investigate the effects of light, temperature, soil moisture, and precipitation on the emergence and parasitism of parasitoid releases of unprotected and encapsulated pupae. The presence of light favored the parasitism of Trichogramma pretiosum Riley, 1879, and Telenomus remus (Nixon, 1937) but did not impact the parasitism of Telenomus podisi (Ashmead, 1893). The release strategy adopted (release of encapsulated or unprotected pupae) also impacted the results. On one hand, card capsules gave protection against rainfall, limited to 10 mm regarding Tr. pretiosum, while on the other hand, card capsules led to a reduction in the number of captured adults for Te. podisi at 25°C and 30°C. Therefore, Tr. pretiosum, Te. remus, and Te. podisi can be released using both encapsulated and unprotected pupae, with advantages and disadvantages for each strategy, depending on each studied environmental variable. In addition, parasitoid pupae should be released so that the majority emerge during daylight, especially for Te. remus and Tr. pretiosum, since parasitism was greatly reduced in dark environments. Telenomus podisi is not affected by this variable as it demonstrated similar parasitism in light and dark environments.

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BACKGROUND: Economic thresholds (ETs) are well-established for defoliation of soybean, Glycine max, and have been updated for many of the newer cultivars; however, there is increasing grower adoption of cultivars with a reduced leaf area index (LAI). It is of theoretical and practical interest to determine low LAI cultivar tolerance to defoliation. We conducted experiments during two consecutive crop seasons (2017/2018 and 2018/2019) using three soybean cultivars (NS 5959 IPRO, NS 5445 IPRO, and DON MARIO 5.8i) and three defoliation levels (0%, 16.7%, and 33.3%) to evaluate the tolerance of reduced LAI soybean cultivars under different defoliation levels. RESULTS: We observed differences among cultivar's LAI during plant development during both years. Soybean LAI was reduced with increasing defoliation intensity. Tested continuous defoliation levels from plant development stages of V2 to R6 reduced the weight of 1000 seeds and yield but did not impact oil or protein content. CONCLUSIONS: Despite our findings that current ET for defoliators in soybean (30% defoliation during vegetative stage and 15% defoliation during reproductive stage) are valid, it is important to consider that continuous defoliation injury impacts the capacity of the plant to respond to injury and must be further evaluated for ET refinement in future research. © 2020 Society of Chemical Industry.

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In order to optimize the mass rearing of Telenomus podisi Ashmead (Hymenoptera: Platygastridae) for augmentative biological control we tested the suitability of different artificial diets with respect to egg production of Euschistus heros (F.) (Hemiptera: Pentatomidae). For this purpose, biological parameters of E. heros and T. podisi were evaluated in experimental trial with these diets. All tested artificial diets supported the rearing of E. heros. However, female and adult life history traits including longevity, total oviposition, nymph developmental time, and fertility were altered, with poorer results than under the natural diet. However, because of the higher economic cost of the natural diet, its replacement with artificial diets could be beneficial. Since stink bug reared on artificial diet has shorter lifespan, an alternative to overcome this issue is to replace earlier the insects in the insect facility what could still be cheaper than insects reared on natural diet. It was also noted the possibility of using artificial diets without lyophilized components what can further reduce the cost of rearing.

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The study of the technical and economic aspects of rearing natural enemies is essential for its effective use as a biological control agent in the field. The aim of this study was to determine the cost of production of the parasitoid, Telenomus remus (Nixon; Hymenoptera: Platygastridae), reared in eggs of its natural host, Spodoptera frugiperda (J. E. Smith; Lepidoptera: Noctuidae), and the alternative host, Corcyra cephalonica (Stainton; Lepidoptera: Pyralidae). The insects were reared in accordance with their respective methodologies of laboratory rearing. The cost of production of this biocontrol agent is US$ 0.0004 when reared with S. frugiperda eggs and US$ 0.0002 with C. cephalonica eggs.

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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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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.

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.

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Telenomus remus releasing numbers may vary depending on the crop, plant architecture and/or the plant phenological stage. Thus, we examined the number of parasitoids needed for effective pest control of Spodoptera frugiperda on corn, cotton and soybean. In all crops, the parasitism response in relation to increasing numbers of the parasitoids had a quadratic effect. In corn, the maximum parasitism observed was 99.8% and 96.8% at a parasitoid releasing number of 0.231 and 0.264 T. remus females per S. frugiperda egg at phenological stages V4 and V10, respectively. Differently, in cotton and soybean, the highest parasitim were recorded using the highest tested T. remus releasing numbers (0.297 parasitoid per S. frugiperda egg). In cotton, it was 77.8% and 73.1% at the vegetative and reproductive stages, respectively and in soybean, it was 77.3% and 54.4% also at the vegetative and reproductive stages. Thus, the appropriated T. remus releasing number might vary accordingly to the crop and plant phenological stage, being higher for soybean and cotton and lower for corn.

O número de Telenomus remus a ser liberado pode ser variável, dependendo de cada cultura, da arquitetura da planta e/ou do seu estágio fenológico. Assim, foi examinado o número de parasitoides necessários para obter o controle efetivo de Spodoptera frugiperda em milho, algodão e soja. Em todas as culturas, a resposta do parasitismo em relação ao número crescente de parasitoides teve um efeito quadrático. Em milho, o parasitismo máximo observado foi de 99,8% e 96,8% em um número de parasitoides liberados de 0,231 e 0,264 fêmeas de T. remus por ovo de S. frugiperda nos estádios fenológicos V4 e V10, respectivamente. Diferentemente, em algodão e soja, os maiores parasitismos foram verificados liberando o maior número de fêmeas de T. remus testados (0,297 fêmeas por ovos de S. frugiperda). Em algodão, foi 77,8% e 73,1% nos estágios vegetativo e reprodutivo, respectivamente e, em soja, foi 77,3% e 54,4% também nos estágios vegetativo e reprodutivo. Assim, o número apropriado de T. remus a ser liberado pode variar de acordo com a cultura e com o estágio fenológico da planta, sendo mais elevado para soja e algodão e mais baixo para milho.

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Telenomus remus releasing numbers may vary depending on the crop, plant architecture and/or the plant phenological stage. Thus, we examined the number of parasitoids needed for effective pest control of Spodoptera frugiperda on corn, cotton and soybean. In all crops, the parasitism response in relation to increasing numbers of the parasitoids had a quadratic effect. In corn, the maximum parasitism observed was 99.8% and 96.8% at a parasitoid releasing number of 0.231 and 0.264 T. remus females per S. frugiperda egg at phenological stages V4 and V10, respectively. Differently, in cotton and soybean, the highest parasitim were recorded using the highest tested T. remus releasing numbers (0.297 parasitoid per S. frugiperda egg). In cotton, it was 77.8% and 73.1% at the vegetative and reproductive stages, respectively and in soybean, it was 77.3% and 54.4% also at the vegetative and reproductive stages. Thus, the appropriated T. remus releasing number might vary accordingly to the crop and plant phenological stage, being higher for soybean and cotton and lower for corn.

O número de Telenomus remus a ser liberado pode ser variável, dependendo de cada cultura, da arquitetura da planta e/ou do seu estágio fenológico. Assim, foi examinado o número de parasitoides necessários para obter o controle efetivo de Spodoptera frugiperda em milho, algodão e soja. Em todas as culturas, a resposta do parasitismo em relação ao número crescente de parasitoides teve um efeito quadrático. Em milho, o parasitismo máximo observado foi de 99,8% e 96,8% em um número de parasitoides liberados de 0,231 e 0,264 fêmeas de T. remus por ovo de S. frugiperda nos estádios fenológicos V4 e V10, respectivamente. Diferentemente, em algodão e soja, os maiores parasitismos foram verificados liberando o maior número de fêmeas de T. remus testados (0,297 fêmeas por ovos de S. frugiperda). Em algodão, foi 77,8% e 73,1% nos estágios vegetativo e reprodutivo, respectivamente e, em soja, foi 77,3% e 54,4% também nos estágios vegetativo e reprodutivo. Assim, o número apropriado de T. remus a ser liberado pode variar de acordo com a cultura e com o estágio fenológico da planta, sendo mais elevado para soja e algodão e mais baixo para milho.

RESUMO

Telenomus remus releasing numbers may vary depending on the crop, plant architecture and/or the plant phenological stage. Thus, we examined the number of parasitoids needed for effective pest control of Spodoptera frugiperda on corn, cotton and soybean. In all crops, the parasitism response in relation to increasing numbers of the parasitoids had a quadratic effect. In corn, the maximum parasitism observed was 99.8% and 96.8% at a parasitoid releasing number of 0.231 and 0.264 T. remus females per S. frugiperda egg at phenological stages V4 and V10, respectively. Differently, in cotton and soybean, the highest parasitim were recorded using the highest tested T. remus releasing numbers (0.297 parasitoid per S. frugiperda egg). In cotton, it was 77.8% and 73.1% at the vegetative and reproductive stages, respectively and in soybean, it was 77.3% and 54.4% also at the vegetative and reproductive stages. Thus, the appropriated T. remus releasing number might vary accordingly to the crop and plant phenological stage, being higher for soybean and cotton and lower for corn.

O número de Telenomus remus a ser liberado pode ser variável, dependendo de cada cultura, da arquitetura da planta e/ou do seu estágio fenológico. Assim, foi examinado o número de parasitoides necessários para obter o controle efetivo de Spodoptera frugiperda em milho, algodão e soja. Em todas as culturas, a resposta do parasitismo em relação ao número crescente de parasitoides teve um efeito quadrático. Em milho, o parasitismo máximo observado foi de 99,8% e 96,8% em um número de parasitoides liberados de 0,231 e 0,264 fêmeas de T. remus por ovo de S. frugiperda nos estádios fenológicos V4 e V10, respectivamente. Diferentemente, em algodão e soja, os maiores parasitismos foram verificados liberando o maior número de fêmeas de T. remus testados (0,297 fêmeas por ovos de S. frugiperda). Em algodão, foi 77,8% e 73,1% nos estágios vegetativo e reprodutivo, respectivamente e, em soja, foi 77,3% e 54,4% também nos estágios vegetativo e reprodutivo. Assim, o número apropriado de T. remus a ser liberado pode variar de acordo com a cultura e com o estágio fenológico da planta, sendo mais elevado para soja e algodão e mais baixo para milho.

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The success of Trichogramma spp. releases in biological control programs relies upon the knowledge of the parasitoid bio-ecological characteristics and the parasitoid interaction with the target pest. Therefore, this research aimed to evaluate T. pretiosum host preference among eggs of S. frugiperda, S. albula, S. eridania, A. gemmatalis, P. includens, D. saccharalis and A. kuehniella. Polyethylene cages were set to test host preference of T. pretiosum comparing each two groups of host species. The evaluated parameter was parasitism (%) and parasitoid emergence (%). T. pretiosum females parasitized preferably A. kuehniella eggs. However, in the bioassay with A. gemmatalis X P. includens and D. saccharalis X S. frugiperda there was no difference in the parasitism. Then, in the free choice test, in the absence of the host in which the parasitoid was reared (A. kuehniella), T. pretiosum shows no host preference indicating the existence of pre-imaginal conditioning acquired during larval development. The parasitism viability results were variable among the different tested hosts.

O sucesso das liberações de Trichogramma spp. depende basicamente do conhecimento das características bioecológicas do parasitoide e da sua interação com o hospedeiro alvo. Assim, o objetivo deste trabalho foi avaliar a preferência hospedeira de T. pretiosum entre os ovos de S. frugiperda, S. albula, S. eridania, A. gemmatalis, P. includens, D. saccharalis e A. kuehniella. Para os testes de preferência, foram instaladas arenas com garrafas de polietileno e, em cada uma delas, foi colocada uma cartela com ovos de duas espécies de hospedeiros e uma fêmea do parasitoide por 24 horas. Os parâmetros avaliados foram o parasitismo (%) e a emergência (%). As fêmeas de T. pretiosum apresentaram preferência pelos ovos de A. kuehniella. No entanto, nos ensaios com A. gemmatalis X P. includens e D. saccharalis X S. frugiperda, não ocorreram diferenças no parasitismo. Assim, pode-se afirmar que, nos teste de livre escolha, na ausência do hospedeiro em que os parasitoides foram multiplicados (A. kuehniella), as fêmeas não apresentaram preferência ao parasitismo, o que indica a existência de condicionamento pré-imaginal do parasitoide. Os resultados da viabilidade dos ovos parasitados por T. pretiosum variaram entre os diferentes hospedeiros testados.

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This study evaluated the effects of different soybean injury levels at early growth stages of the plants. The experiments were carried out in two different growing seasons, using a randomized complete block design, with 11 treatments in the first and 10 treatments in the second season, and four replications. The 'BRS 133' soybean cultivar was used, and the injury levels tested were: 1-Control; 2-Removal of 1 cotyledon; 3-Removal of both cotyledons; 4-Removal of both cotyledons + 1 unifoliate leaf; 5-Removal of both cotyledons + both unifoliate leaves; 6-Removal of 1 unifoliate leaf; 7-removal of both unifoliate leaves; 8-Cut below unifoliate leaves; 9-Removal of trifoliate leaf sprouts; 10-Total defoliation; 11-Total defoliation + removal of apical bud (only in the first trial). Injury was manually imposed, and insecticides were applied weekly to prevent injury by insects. The results showed that the soybean yield was reduced only when the injury was severe enough to cause plant stand reductions as a consequence of plant death. This occurred for treatments 5, 10 and 11. Under the other treatments, the soybean plants were able to recover. These findings show that the recommended economic threshold of 30% defoliation to initiate pest control is safe, and should be accepted by growers.

Este estudo avaliou os efeitos de diferentes níveis de injúria nos estádios iniciais de desenvolvimento das plantas de soja. Os experimentos foram realizados em duas diferentes safras agrícolas em delineamento de blocos completos casualizados, com 11 tratamentos na primeira e 10 tratamentos na segunda safra, e quatro repetições. A cultivar utilizada foi a 'BRS 133' e os níveis de injúria foram: 1-Testemunha; 2-Remoção de 1 cotilédone; 3-Remoção de ambos os cotilédones; 4-Remoção de ambos os cotilédones + 1 folha unifoliolada; 5-Remoção de ambos cotilédones + ambas as folhas unifolioladas; 6-Remoção de 1 folha unifoliolada; 7-Remoção de ambas as folhas unifolioladas; 8-Corte abaixo das folhas unifoliadas; 9-Remoção do broto das folhas trifolioladas; 10-Desfolha total; 11-Desfolha total + remoção da gema apical (apenas no primeiro ensaio). A injúria foi realizada manualmente e inseticidas foram aplicados semanalmente para impedir injúria por insetos. Os resultados evidenciaram que a produção de soja foi reduzida somente quando a injúria foi severa o suficiente para provocar a redução do estande em consequência da morte de plantas. Isso ocorreu nos tratamentos 5, 10 e 11. Nos demais tratamentos, as plantas foram capazes de se recuperar, o que comprova que o nível de ação de 30% de desfolha que é recomendado para iniciar o controle é seguro e deve ser respeitado pelos sojicultores.

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In recent crop seasons, the whitefly, Bemisia tabaci biotype B has become a serious pest in soybean crops due to high infestations and its control difficulties. Therefore, it is important to search control alternatives in the integrated pest management approach. Thus, it was evaluated in this study the efficacy of the whitefly control using different insecticides in greenhouse conditions and their selectivity to the parasitoids Encarsia formosa, Trichogramma pretiosum and Telenomus remus. Buprofezin 150 g. a.i.ha-1 + mineral oil 0.2% v/v and pyriproxyfen 100 g. a.i.ha-1 were considered the best options for the whitefly management due to combine good pest control efficacy with higher selectivity to the parasitoids except Encarsia formosa for which no treatment was classified as harmless. Betacyflutrin 9.375 + imidacloprid 75 g. i.a. ha-1 was efficient on controlling whiteflies nymphs but was not harmless to the studied natural enemies. In general, the treatments including pyretroids compounds (betacyflutrin 9.375 + imidacloprid 75 + spiromesifen 60, betacyflutrin 9.375 + imidacloprid 75 and lambda-cyhalothrin 26.5 + thiametoxan 35.25 g. a.i. ha-1) were the most harmful to the evaluated parasitoids and therefore it use should be avoid whenever possible.

Nas últimas safras a mosca-branca, Bemisia tabaci biótipo B (Hemiptera: Aleyrodidae) tornou-se praga de importância econômica para a cultura da soja devido à ocorrência de altas infestações e à dificuldade de controle desta praga. Sendo assim, é importante buscar alternativas de manejo com base em um programa de manejo integrado de pragas. Assim, avaliaram-se neste trabalho a eficiência de diferentes inseticidas no controle da mosca-branca em casa-de-vegetação e a seletividade destes aos parasitoides Encarsia formosa, Trichogramma pretiosum e Telenomus remus. Buprofezina 150 g i.a. ha-1 + óleo mineral 0,2% v/v e piriproxifem 100 g. i.a. ha-1 foram consideradas as melhores opções para uso no manejo da mosca-branca devido à boa eficiência de controle da praga associada com a maior seletividade aos parasitoides estudados à exceção de Encarsia formosa para o qual nenhum dos tratamentos avaliados foi classificado como seletivo. Beta-ciflutrina 9,375 +imidacloprido 75 g. i.a. ha-1 foi eficiente no controle de ninfas, mas não foi seletivo aos inimigos naturais avaliados. Em geral, os tratamentos contendo piretróides na sua composição (beta-ciflutrina 9,375 + imidacloprido 75 + espiromesifeno 60 g. i.a. ha-1; beta-ciflutrina 9,375 + imidacloprido 75 g. i.a. ha-1 e lambda-cialotrina 26,5 + tiametoxam 35,25 g i.a. ha-1) foram os mais nocivos aos parasitoides avaliados, portanto seu uso d

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This study evaluated the effects of different soybean injury levels at early growth stages of the plants. The experiments were carried out in two different growing seasons, using a randomized complete block design, with 11 treatments in the first and 10 treatments in the second season, and four replications. The 'BRS 133' soybean cultivar was used, and the injury levels tested were: 1-Control; 2-Removal of 1 cotyledon; 3-Removal of both cotyledons; 4-Removal of both cotyledons + 1 unifoliate leaf; 5-Removal of both cotyledons + both unifoliate leaves; 6-Removal of 1 unifoliate leaf; 7-removal of both unifoliate leaves; 8-Cut below unifoliate leaves; 9-Removal of trifoliate leaf sprouts; 10-Total defoliation; 11-Total defoliation + removal of apical bud (only in the first trial). Injury was manually imposed, and insecticides were applied weekly to prevent injury by insects. The results showed that the soybean yield was reduced only when the injury was severe enough to cause plant stand reductions as a consequence of plant death. This occurred for treatments 5, 10 and 11. Under the other treatments, the soybean plants were able to recover. These findings show that the recommended economic threshold of 30% defoliation to initiate pest control is safe, and should be accepted by growers.

Este estudo avaliou os efeitos de diferentes níveis de injúria nos estádios iniciais de desenvolvimento das plantas de soja. Os experimentos foram realizados em duas diferentes safras agrícolas em delineamento de blocos completos casualizados, com 11 tratamentos na primeira e 10 tratamentos na segunda safra, e quatro repetições. A cultivar utilizada foi a 'BRS 133' e os níveis de injúria foram: 1-Testemunha; 2-Remoção de 1 cotilédone; 3-Remoção de ambos os cotilédones; 4-Remoção de ambos os cotilédones + 1 folha unifoliolada; 5-Remoção de ambos cotilédones + ambas as folhas unifolioladas; 6-Remoção de 1 folha unifoliolada; 7-Remoção de ambas as folhas unifolioladas; 8-Corte abaixo das folhas unifoliadas; 9-Remoção do broto das folhas trifolioladas; 10-Desfolha total; 11-Desfolha total + remoção da gema apical (apenas no primeiro ensaio). A injúria foi realizada manualmente e inseticidas foram aplicados semanalmente para impedir injúria por insetos. Os resultados evidenciaram que a produção de soja foi reduzida somente quando a injúria foi severa o suficiente para provocar a redução do estande em consequência da morte de plantas. Isso ocorreu nos tratamentos 5, 10 e 11. Nos demais tratamentos, as plantas foram capazes de se recuperar, o que comprova que o nível de ação de 30% de desfolha que é recomendado para iniciar o controle é seguro e deve ser respeitado pelos sojicultores.

RESUMO

The success of Trichogramma spp. releases in biological control programs relies upon the knowledge of the parasitoid bio-ecological characteristics and the parasitoid interaction with the target pest. Therefore, this research aimed to evaluate T. pretiosum host preference among eggs of S. frugiperda, S. albula, S. eridania, A. gemmatalis, P. includens, D. saccharalis and A. kuehniella. Polyethylene cages were set to test host preference of T. pretiosum comparing each two groups of host species. The evaluated parameter was parasitism (%) and parasitoid emergence (%). T. pretiosum females parasitized preferably A. kuehniella eggs. However, in the bioassay with A. gemmatalis X P. includens and D. saccharalis X S. frugiperda there was no difference in the parasitism. Then, in the free choice test, in the absence of the host in which the parasitoid was reared (A. kuehniella), T. pretiosum shows no host preference indicating the existence of pre-imaginal conditioning acquired during larval development. The parasitism viability results were variable among the different tested hosts.

O sucesso das liberações de Trichogramma spp. depende basicamente do conhecimento das características bioecológicas do parasitoide e da sua interação com o hospedeiro alvo. Assim, o objetivo deste trabalho foi avaliar a preferência hospedeira de T. pretiosum entre os ovos de S. frugiperda, S. albula, S. eridania, A. gemmatalis, P. includens, D. saccharalis e A. kuehniella. Para os testes de preferência, foram instaladas arenas com garrafas de polietileno e, em cada uma delas, foi colocada uma cartela com ovos de duas espécies de hospedeiros e uma fêmea do parasitoide por 24 horas. Os parâmetros avaliados foram o parasitismo (%) e a emergência (%). As fêmeas de T. pretiosum apresentaram preferência pelos ovos de A. kuehniella. No entanto, nos ensaios com A. gemmatalis X P. includens e D. saccharalis X S. frugiperda, não ocorreram diferenças no parasitismo. Assim, pode-se afirmar que, nos teste de livre escolha, na ausência do hospedeiro em que os parasitoides foram multiplicados (A. kuehniella), as fêmeas não apresentaram preferência ao parasitismo, o que indica a existência de condicionamento pré-imaginal do parasitoide. Os resultados da viabilidade dos ovos parasitados por T. pretiosum variaram entre os diferentes hospedeiros testados.

RESUMO

The success of Trichogramma spp. releases in biological control programs relies upon the knowledge of the parasitoid bio-ecological characteristics and the parasitoid interaction with the target pest. Therefore, this research aimed to evaluate T. pretiosum host preference among eggs of S. frugiperda, S. albula, S. eridania, A. gemmatalis, P. includens, D. saccharalis and A. kuehniella. Polyethylene cages were set to test host preference of T. pretiosum comparing each two groups of host species. The evaluated parameter was parasitism (%) and parasitoid emergence (%). T. pretiosum females parasitized preferably A. kuehniella eggs. However, in the bioassay with A. gemmatalis X P. includens and D. saccharalis X S. frugiperda there was no difference in the parasitism. Then, in the free choice test, in the absence of the host in which the parasitoid was reared (A. kuehniella), T. pretiosum shows no host preference indicating the existence of pre-imaginal conditioning acquired during larval development. The parasitism viability results were variable among the different tested hosts.

O sucesso das liberações de Trichogramma spp. depende basicamente do conhecimento das características bioecológicas do parasitoide e da sua interação com o hospedeiro alvo. Assim, o objetivo deste trabalho foi avaliar a preferência hospedeira de T. pretiosum entre os ovos de S. frugiperda, S. albula, S. eridania, A. gemmatalis, P. includens, D. saccharalis e A. kuehniella. Para os testes de preferência, foram instaladas arenas com garrafas de polietileno e, em cada uma delas, foi colocada uma cartela com ovos de duas espécies de hospedeiros e uma fêmea do parasitoide por 24 horas. Os parâmetros avaliados foram o parasitismo (%) e a emergência (%). As fêmeas de T. pretiosum apresentaram preferência pelos ovos de A. kuehniella. No entanto, nos ensaios com A. gemmatalis X P. includens e D. saccharalis X S. frugiperda, não ocorreram diferenças no parasitismo. Assim, pode-se afirmar que, nos teste de livre escolha, na ausência do hospedeiro em que os parasitoides foram multiplicados (A. kuehniella), as fêmeas não apresentaram preferência ao parasitismo, o que indica a existência de condicionamento pré-imaginal do parasitoide. Os resultados da viabilidade dos ovos parasitados por T. pretiosum variaram entre os diferentes hospedeiros testados.

RESUMO

In recent crop seasons, the whitefly, Bemisia tabaci biotype B has become a serious pest in soybean crops due to high infestations and its control difficulties. Therefore, it is important to search control alternatives in the integrated pest management approach. Thus, it was evaluated in this study the efficacy of the whitefly control using different insecticides in greenhouse conditions and their selectivity to the parasitoids Encarsia formosa, Trichogramma pretiosum and Telenomus remus. Buprofezin 150 g. a.i.ha-1 + mineral oil 0.2% v/v and pyriproxyfen 100 g. a.i.ha-1 were considered the best options for the whitefly management due to combine good pest control efficacy with higher selectivity to the parasitoids except Encarsia formosa for which no treatment was classified as harmless. Betacyflutrin 9.375 + imidacloprid 75 g. i.a. ha-1 was efficient on controlling whiteflies nymphs but was not harmless to the studied natural enemies. In general, the treatments including pyretroids compounds (betacyflutrin 9.375 + imidacloprid 75 + spiromesifen 60, betacyflutrin 9.375 + imidacloprid 75 and lambda-cyhalothrin 26.5 + thiametoxan 35.25 g. a.i. ha-1) were the most harmful to the evaluated parasitoids and therefore it use should be avoid whenever possible.

Nas últimas safras a mosca-branca, Bemisia tabaci biótipo B (Hemiptera: Aleyrodidae) tornou-se praga de importância econômica para a cultura da soja devido à ocorrência de altas infestações e à dificuldade de controle desta praga. Sendo assim, é importante buscar alternativas de manejo com base em um programa de manejo integrado de pragas. Assim, avaliaram-se neste trabalho a eficiência de diferentes inseticidas no controle da mosca-branca em casa-de-vegetação e a seletividade destes aos parasitoides Encarsia formosa, Trichogramma pretiosum e Telenomus remus. Buprofezina 150 g i.a. ha-1 + óleo mineral 0,2% v/v e piriproxifem 100 g. i.a. ha-1 foram consideradas as melhores opções para uso no manejo da mosca-branca devido à boa eficiência de controle da praga associada com a maior seletividade aos parasitoides estudados à exceção de Encarsia formosa para o qual nenhum dos tratamentos avaliados foi classificado como seletivo. Beta-ciflutrina 9,375 +imidacloprido 75 g. i.a. ha-1 foi eficiente no controle de ninfas, mas não foi seletivo aos inimigos naturais avaliados. Em geral, os tratamentos contendo piretróides na sua composição (beta-ciflutrina 9,375 + imidacloprido 75 + espiromesifeno 60 g. i.a. ha-1; beta-ciflutrina 9,375 + imidacloprido 75 g. i.a. ha-1 e lambda-cialotrina 26,5 + tiametoxam 35,25 g i.a. ha-1) foram os mais nocivos aos parasitoides avaliados, portanto seu uso d

RESUMO

Biological control agent preservation is crucial to the integrated pest management success. However, chemical control is yet useful for crop production. Thus, pesticide selectivity to beneficial insects is a feature that must always be taken into account in order to choose the best chemical. Therefore, this research studied the impact caused by different pesticides in the egg parasitoid, Telenomus remus Nixon (Hymenoptera: Scelionidae) emergence, when sprayed on the larvae and pupae stage (Egg masses from 100 to 150 eggs of Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) six and ten days after the parasitism, respectively). Three trials, with 11 treatments and 5 repetitions, were carried out in the laboratory with insecticides, fungicides and herbicides. Each test was carried out with 10 treatments of chemicals and water as control. All chemicals were tested at rates used in soybean crops. Eggs of S. frugiperda parasitized by T. remus, were immersed in the treatments for five seconds. After completely dry, they were placed in plastic bags until the emergence of adults of parasitoids. The viability of parasitism was evaluated and the reduction in the emergence of the parasitoids classified according to the rules of the International Organization for Biological Control (IOBC). The results showed that the insect growth-regulating (IGR) insecticides flufenoxuron, diflubenzuron, methoxyfenozide as well as the insecticides imidacloprid + beta-cyfluthrin and acephate were harmless to the parasitoid immature stages . Spinosad was classified as harmless for larvae of T. remus. Gama-cyhalothrin was slightly harmful to larvae and harmless to pupa of T. remus. Bifenthrin and chlorpyrifos were, respectively, slightly harmful and harmful to both stages of development of T. remus development. Regarding to the tested herbicides, 2,4-D, s-metolachlor, flumioxazin, paraquat dichloride + diuron, paraquat dichloride and glyphosate (Roundup Transorb®) were harmless. However, glyphosate + imazethapyr, clomazone, glyphosate (Gliz®), glyphosate (Roundup Ready®) were harmless to the larvae stage and slightly harmful (class 2) to T. remus pupae. Similar results were obtained with the fungicides flutriafol + tiofanate, carbenzadin, tebuconazol + trifloxystrobin and azoxystrobin + ciproconazol which were classified as harmless. Tiofanate-metil, tebuconazol and epoxyconazol + pyraclostrobin were slightly harmful to larvae and pupae. Inversely, epoxyconazol and azoxystrobin were harmless to larvae and slightly harmful to pupae. Flutriafol was classified as slightly harmful to both development stages of T. remus.

A preservação dos agentes de controle biológico no agroecossistema é indispensável para o sucesso do manejo integrado de pragas. Entretanto, o controle químico de pragas ainda é indispensável em diversas culturas. Nesse contexto, a seletividade dos agrotóxicos aos inimigos naturais deve ser sempre considerada na escolha do melhor produto. Portanto, este estudo verificou o impacto causado por diferentes agrotóxicos na emergência do parasitoide de ovos Telenomus remus Nixon (Hymenoptera: Scelionidae), quando aplicados nas fases de larva e pupa (posturas de 100 a 150 ovos de Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) seis e 10 dias após o parasitismo, respectivamente). Três ensaios, com 11 tratamentos e cinco repetições, foram conduzidos em laboratório com inseticidas, fungicidas e herbicidas, respectivamente. Cada ensaio foi conduzido com 10 tratamentos de agrotóxicos e água como testemunha seletiva. Todos os produtos fitossanitários foram testados nas doses utilizadas na cultura da soja. Ovos de S. frugiperda parasitados por T. remus foram imersos nos tratamentos por cinco segundos e, após secagem total, foram acondicionados em sacos plásticos até a emergência dos adultos dos parasitoides. A viabilidade do parasitismo foi avaliada, e a redução na emergência dos parasitoides foi classificada segundo as normas da International Organization for Biological Control (IOBC). Os resultados mostraram que os inseticidas do grupo dos reguladores de crescimento, como o flufenoxurom, diflubenzurom e metoxifenozido e também os inseticidas imidacloprido + beta-ciflutrina e acefato, foram seletivos às fases imaturas do parasitoide. Espinosade foi classificado como inócuo para larvas de T. remus. Gama-cialotrina foi levemente nocivo para larvas e inócuo para pupas. Bifentrina e clorpirifós foram, respectivamente, levemente nocivo e nocivo para ambas as fases de desenvolvimento de T. remus. Com relação aos herbicidas testados, 2,4-D, S-metolacloro, flumioxazina, dicloreto de paraquate + diurom, dicloreto de paraquate e glifosato (Roundup Transorb®) foram seletivos. Entretanto, glifosato + imazetapir, clomazona, glifosato (Gliz®), glifosato (Roundup Ready®) foram seletivos para a fase de larva e levemente nocivos (classe 2) para a fase de pupa de T. remus. Resultados semelhantes foram obtidos com os fungicidas flutriafol + tiofanato metílico, carbenzadim, trifloxistrobina + tebuconazole e azoxistrobina + ciproconazole, que foram classificados como inócuos. Tiofanato-metílico, tebuconazole e epoxiconazole + piraclostrobina foram levemente nocivos para larvas e inócuos para pupas. Inversamente, epoxiconazole e azoxistrobina foram seletivos para a fase de larva e levemente nocivos para a fase de pupa do parasitoide. Flutriafol foi classificado como levemente nocivo para ambas as fases de T. remus.