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BACKGROUND: Plant volatile organic compounds (VOCs) play a crucial role in mediating interactions between plants, herbivores and natural enemies. Among these VOCs, methyl salicylate and (E,E)-α-farnesene are emitted as herbivore-induced plant volatiles (HIPVs) by soybean plants in response to feeding by the brown stink bug Eushistus heros. These HIPVs function as synomones, influencing the foraging behaviour of the egg parasitoid, Telenomus podisi, the main natural enemy of E. heros, one of the major soybean pests in Brazil. RESULTS: Laboratory experiments showed that two soybean cultivars, BRS 7580 and BRS 7880, produced similar qualitative blends of HIPVs, with methyl salicylate, (E,E)-α-farnesene and (Z)-3-hexenyl acetate being produced by both cultivars. Soybean cultivar BRS 7580 produced a significant lower amount of HIPVs compared to BRS 7880 but this difference did not affect the attractiveness of the egg parasitoid Telenomus podisi. Field experiments using these two cultivars and synthetic applications of methyl salicylate and (E,E)-α-farnesene showed a substantial increase in egg parasitism in all treated areas. Parasitism rates ranged from 50% to 80% in areas where these HIPVs were deployed, compared to only 10% in untreated control areas. CONCLUSIONS: The egg parasitoid Telenomus podisi demonstrated an adept ability in recognising between HIPVs in soybean blends, even in the presence of significant quantitative differences. The results from the field experiment showed the potential of HIPVs in attracting natural enemies to specific target areas within fields. (E,E)-α-Farnesene showed an improved action during the later stages of soybean growth, notably at R6. In addition, this volatile attracted other families of natural enemies. © 2024 Society of Chemical Industry.

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The novel ingestion bioassay method was developed for detecting and monitoring resistance of Euschistus heros by encapsulating an artificial liquid diet using Parafilm®. This methodology was compared with the tarsal contact (vial test) and topical application methods for thiamethoxam, imidacloprid, and lambda-cyhalothrin. The best bioassay method for the neonicotinoid insecticides thiamethoxam and imidacloprid was ingestion. For pyrethroid insecticide lambda-cyhalothrin, the best result was obtained by topical application. Using the best bioassay method for each insecticide, the susceptibility to these insecticides was monitored in 30 populations of E. heros collected from soybean crops in Brazil from 2018 to 2020. High variations in susceptibility to thiamethoxam (resistance ratios, 1.6-22 times), imidacloprid (resistance ratios, 1.6-22 times), and lambda-cyhalothrin (resistance ratios, 5-40 times) were detected among the evaluated E. heros populations. In order to monitor the susceptibility of E. heros to insecticides, diagnostic concentrations were defined based on the LC99 of the susceptible reference population: 5.65 µL of a.i./mL for thiamethoxam, 12.45 µL of a.i./mL for imidacloprid, and 0.20 µg of a.i./insect for lambda-cyhalothrin. Subsequently, we select an E. heros strain resistant to neonicotinoid insecticides and another to lambda-cyhalothrin. The resistance ratios obtained after seven selection cycles were 66, 41 and 44 times for thiamethoxam, imidacloprid and lambda-cyhalothrin, respectively.

RESUMO

Three strains of fungi belonging to the genus Metarhizium Sorokin (ARSEF 4556, ARSEF 3297, native strain) were assayed against adults and nymphs of the Neotropical brown stinkbug Euschistus heros (F.) and the green-belly stinkbug Dichelops furcatus (F.). The most virulent strain, ARSEF 4556, caused over 90% mortality. The average survival time of the second and fifth instar nymphs and adults following immersion in 1 × 108 conidia ml-1 was 4.8, 5.7, and 5.2 d, respectively. The second instar nymphs were more susceptible than the adults. The LC50 values and median survival times for second instar and adult E. heros were 1.6 × 107 and 3.1 × 107 conidia ml-1 and 6 and 8 d, respectively. Eggs of E. heros and the closely related stinkbug, D. furcatus, were highly susceptible to ARSEF 4556 with the mean mortality of eggs immersed in 1 × 108 conidia ml-1 being 77.4% and 89.7%, respectively. The strain 3297 showed also good aptitudes for stinkbugs control with mortalities higher than 80% against nymphs and adults and eggs mortalities of 75.5% for E. heros and 79.6% for D. furcatus. This study has shown that it is possible to have a two-pronged control strategy, targeting adults and to reduce oviposition and targeting egg clusters to prevent emergence and dispersal of nymphs. Besides early instars of nymphs have been shown to be more susceptible to the fungal strains than late instars and adults.

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Successful biological control requires detailed knowledge about the mass rearing conditions of the control agents in order to ensure higher quality of field-released insects. Thus, we investigated whether rearing fluctuating thermal condition would affect the fitness and costs of the parasitoid wasp Telenomus podisi Ashmead (a biocontrol agent used for controlling the Neotropical brown stink bug Euschistus heros (Fabricius)) when compared with parasitoid reared at constant temperature condition, which is commonly used in insect facilities. Parasitoids were reared under either constant (continuous exposure at 25 ± 2°C) or fluctuating temperature conditions (i.e., 30 ± 2°C during day and 20 ± 2°C at night) during four consecutive generations. Our results indicated that tested fluctuating temperature is more suitable for rearing of T. podisi as such temperature condition not only resulted in fitness benefits (e.g., shorter developmental time, longer female longevity, higher fecundity/fertility) but also reduced (approximately 23.5%) the estimated costs for producing the parasitoids. Furthermore, rearing T. podisi under fluctuating temperatures improved tolerance to low constant temperatures (i.e., 20°C) without changing the tolerance to constant high temperatures (30°C) in the fourth generation. Surprisingly, even parasitoids that developed under fluctuating thermal conditions performed better than those reared at constant temperature of 25°C. Collectively, our findings suggest that T. podisi reared under fluctuating thermal condition can tolerate better fluctuating temperatures that normally occur both during long periods of transport and in agricultural ecosystems, which will increase the quality and productivity of mass-reared T. podisi for inundative releases.

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Recent changes in soybean management like the adoption of transgenic crops and no-till farming, in addition to the expansion of cultivated areas into new virgin frontiers, are some of the hypotheses that can explain the rise of secondary pests, such as the Neotropical brown stink bug, Euschistus heros, in Brazil. To better access the risk of increased pests like E. heros and to determine probabilities for insecticide resistance spreading, it is necessary first to access the levels of the genetic diversity, how the genetic diversity is distributed, and how natural selection is acting upon the natural variation. Using the genotyping by sequencing (GBS) technique, we generated ~60,000 single-nucleotide polymorphisms (SNPs) distributed across the E. heros genome to answer some of those questions. The SNP data was used to investigate the pattern of genetic structure, hybridization and natural selection of this emerging pest. We found that E. heros populations presented similar levels of genetic diversity with slightly higher values at several central locations in Brazil. Our results also showed strong genetic structure separating northern and southern Brazilian regions (FST = 0.22; p-value = 0.000) with a very distinct hybrid zone at the central region. The analyses also suggest the possibility that GABA channels and odorant receptors might play a role in the process of natural selection. At least one marker was associated with soybean and beans crops, but no association between allele frequency and cotton was found. We discuss the implications of these findings in the management of emerging pests in agriculture, particularly in the context of large areas of monoculture such as soybean and cotton.

RESUMO

ABSTRACT Extracts of the seeds of Tephrosia vogelii Hook. f. were studied in relation to its chemical composition and toxicity to the brown stink bug Euschistus heros (F.). The extracts were obtained in ethyl acetate and ethanol in the sequence according to the polar nature of the solvents. Extracts were sprayed in concentration of 1.0, 2.5, 5.0, 7.5 and 10% on third-instars nymphs and adults, and mortality was recorded. Presence two rotenoids in ethyl acetate was detected, with analyzed with gas chromatography-mass spectrometry (GC-MS). Crude fraction analyses confirmed the presence of these rotenoids (tephrosin - 2.71% in ethyl acetate and 3.66% in methanol; and deguelin - 10.46% in ethyl acetate and 1.22% in methanol) and three other rotenoids in small amounts. Eight days after applications, ethyl acetate caused more stink bugs mortality and on less time than ethanol extract, because great quantity of rotenoids, as polarity. Concentrations above to 1 and 2.5% of the ethyl acetate extracts caused mortality above 80% of the nymphs and adults of E. heros, respectively. Concentration were considered high, thus chemist analyzes demonstrated high rotenoids presence. In conclusion, seed T. vogelli extracts, rich in deguelin and tephrosin (3:1), cause mortality of E. heros, however, high concentration are necessary.

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To test the hypothesis that the plant stress related elicitor cis-jasmone (cJ) provides protection in soybean pods against the seed-sucking stink bug pest, Euschistus heros, the growth of E. heros on cJ-treated pods was investigated using three soybean cultivars differing in insect susceptibility, i.e. BRS 134 (susceptible), IAC 100 (resistant) and Dowling (resistant). E. heros showed reduced weight gain when fed cJ-treated Dowling, whereas no effect on weight gain was observed when fed other treated cultivars. Using analysis of variance, a three factor (cultivar x treatment x time) interaction was observed with concentrations of the flavonoid glycosides daidzin and genistin, and their corresponding aglycones, daidzein and genistein. There were increases in genistein and genistin concentrations in cJ-treated Dowling at 144 and 120 h post treatment, respectively. Higher concentrations of malonyldaidzin and malonylgenistin in Dowling, compared to BRS 134 and IAC 100, were observed independently of time, the highest concentrations being observed in cJ-treated seeds. Levels of glycitin and malonylglycitin were higher in BRS 134 and IAC 100 compared to Dowling. Canonical variate analysis indicated daidzein (in the first two canonical variates) and genistein (in the first only) as important discriminatory variables. These results suggest that cJ treatment leads to an increase in the levels of potentially defensive isoflavonoids in immature soybean seeds, but the negative effect upon E. heros performance is cultivar-dependent.

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During host selection, physical and chemical stimuli provide important cues that modify search behaviours of natural enemies. We evaluated the influence of volatiles released by eggs and egg extracts of the stink bug Euschistus heros and by soybean plants treated with the eggs and egg extracts on Telenomus podisi foraging behaviour. Responses to volatiles were evaluated in Y-tube olfactometers after exposure to (1) one egg cluster for 24 h; (2) plants with eggs laid by the stink bug, tested at 24, 48, and 72 h after treatment; (3) plants with eggs laid artificially, tested at 24, 48, and 72 h after treatment; and (4) plants treated with acetone or hexane extracts of eggs. Telenomus podisi was attracted to volatiles emitted by one egg cluster and to acetone extracts of one egg cluster, but not to air or acetone controls. There were no responses to odours of plants treated with eggs or egg extracts. Analysis of acetone extracts of egg clusters by gas chromatography revealed the major components were saturated and unsaturated fatty acids, including hexadecanoic acid, linoleic acid, and (Z)-9-octadecenoic acid. Our results suggest that one egg cluster and the acetone extract of one egg cluster contain volatile compounds that can modify T. podisi foraging behaviour, and that the amounts of these compounds, probably together with some minor compounds, are important for host recognition by T. podisi. Also, the oviposition damage or egg extracts on the plant did not elicit indirect defences that attracted Telenomus podisi.

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Plant extract have been recognized as important natural source of insecticide. Herein, we assessed the toxicity of leaves-extract and seeds-extract of Annona mucosa (Annonaceae) against brown stink bug, Euschistus heros (F.) (Hemiptera: Pentatomidae), a soybean pest in Neotropical America. For this, bioassays with nymphs and adults were conducted using the concentrations of 5, 10, 20, 40 and 80 mg.mL-1 of leaves and seeds extract of A. mucosa and DMSO (10%), as control. Ten replicates were conducted by treatment, with five nymphs (3rd instar) by replicate (bioassay with nymphs) and one couple of adults (< 24h of old) by replicate (bioassay with adults). The number of nymphs death (mortality) and survival of adults were assessed. For adults the fecundity (number of eggs) and fertility (number of nymphs hatched) of females also were assessed. The nymphs bioassay has promising results in seeds extract, when compared to leaves extract. The mortality of nymphs treated with seeds extract was dependent-concentration, with increased in mortality in concentrations > 5.0mg.mL-1, while nymphs treated with leaves extract do not exhibit difference between treatments. In adults the survival was reduced, when were treated with seed extract of A. mucosa at concentrations higher than 20mg.mL-1, with reduction up to 92 days in contrast to control. A drastic reduction in the fecundity and fertility was observed, which highlight deleterious action of seed extract against reproductive potential of E. heros. This is the first report about toxicity A. mucosa (leaves and seed) on E. heros, and our results suggest that seeds extract of A. mucosa is promising for control of nymphs and adults of brown stink bug.

Extratos de plantas tem sido reconhecidos como um importante recurso natural de inseticidas. Nesta pesquisa avaliou-se a toxicidade do extrato de folhas e de sementes de Annona mucosa (Annonaceae) sobre o percevejo marrom, Euschistus heros (F.) (Hemiptera: Pentatomidae), uma praga-chave na cultura da soja na America Neotropical. Para tanto, bioensaios com ninfas e adultos foram conduzidos usando as concentrações de 5, 10, 20, 40 e 80 mg.mL-1 do extrato de folhas e sementes de A. mucosa e DMSO (10%), como controle. Dez repetições foram conduzidas por tratamento, com cinco ninfas (3º instar) por repetição (bioensaio com ninfas) e um casal de adultos (< 24h de idade) por repetição (bioensaio com adultos). Foram avaliados o número de ninfas mortas (mortalidade) e a sobrevivência dos adultos. Para fêmeas também foi avaliada a fecundidade (número de ovos) e fertilidade (número de ninfas eclodidas). O extrato de semente de A. mucosa apresentou resultados promissores na mortalidade de ninfas de E. heros, quando comparado ao extrato de folhas. A mortalidade de ninfas tratadas com extrato de semente foi dependente da concentração, com aumento da mortalidade em concentrações > 5,0mg.mL-1, enquanto as ninfas tratadas com extrato de folhas não apresentaram diferença entre os tratamentos. A sobrevivência dos adultos foi reduzida, quando estes foram tratados com extrato de semente de A. mucosa em concentrações maiores que 20mg.mL-1, com redução de até 92 dias, em contraste ao controle. Foi observada uma drástica redução na fecundidade e fertilidade, o que destaca a ação deletéria do extrato de sementes sobre o potencial reprodutivo de E. heros. Este é o primeiro registro sobre a toxicidade de A. mucosa (folhas e sementes) sobre E. heros e os resultados sugerem que o extrato de semente de A. mucosa é promissor para o controle de ninfas e adultos do percevejo marrom.

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This research aimed to evaluate the insecticide potential of the leaves extract of Piper aduncum (L.) (Piperaceae) on development of brown stink bug, Euschistus heros (F.), major pest in soybean crop in Mato Grosso State. For this a bioassay was conducted with eggs, nymphs and adults of this stink bug, using the concentrations 0.5; 1.0; 2.0; 4.0 and 8.0%, of the extract acetonic of P. aduncum and acetone for control. It was evaluated the numbers of unviable eggs, nymphs death and longevity, fecundity and fertility of the adults. In the immersing eggs bioassay, all concentrations greater than 1% unviable more than 70% of the eggs, while in the contact bioassay only 19% of the eggs were unviable in 8% concentration, differing of control. In nymphs bioassay the concentrations of 8% and 4% caused death of 72% and 52%, respectively. In adults bioassay all concentrations tested reduced significantly the survival and reproduction of the insects. Thus is evidence that P. aduncum is a potential plant for stink bug control, because it had deleterious action in all development phases on E. heros.(AU)

Esta pesquisa avaliou o potencial inseticida do extrato de folhas de Piper aduncum (L.) (Piperaceae) sobre o desenvolvimento do percevejo marrom, Euschistus heros (F.), a principal praga da soja no Mato Grosso. Para este estudo, foram realizados bioensaios com ovos, ninfas e adultos do percevejo, utilizando as concentrações de 0,5; 1,0; 2,0; 4,0 e 8,0%, do extrato acetônico de P. aduncum e como controle acetona P.A. Foram avaliados o número de ovos inviáveis, a mortalidade de ninfas e a longevidade, fecundidade e fertilidade dos adultos. No bioensaio de imersão dos ovos, todas as concentrações maiores que 1% tornou inviável mais de 70% dos ovos, enquanto, no bioensaio de contato, apenas 19% dos ovos foram inviabilizados na concentração 8%, diferindo do controle. No bioensaio com ninfas, as concentrações de 8% e 4% ocasionaram morte de 72% e 52%, respectivamente. No bioensaio com adultos, todas as concentrações testadas reduziram significativamente a sobrevivência dos insetos e a reprodução dos insetos. Assim, ficou evidente que P. aduncum é uma planta com potencial para o controle do percevejo marrom, pois teve ação deletéria em todas as fases de desenvolvimento de E. heros.(AU)

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This research aimed to evaluate the insecticide potential of the leaves extract of Piper aduncum (L.) (Piperaceae) on development of brown stink bug, Euschistus heros (F.), major pest in soybean crop in Mato Grosso State. For this a bioassay was conducted with eggs, nymphs and adults of this stink bug, using the concentrations 0.5; 1.0; 2.0; 4.0 and 8.0%, of the extract acetonic of P. aduncum and acetone for control. It was evaluated the numbers of unviable eggs, nymphs death and longevity, fecundity and fertility of the adults. In the immersing eggs bioassay, all concentrations greater than 1% unviable more than 70% of the eggs, while in the contact bioassay only 19% of the eggs were unviable in 8% concentration, differing of control. In nymphs bioassay the concentrations of 8% and 4% caused death of 72% and 52%, respectively. In adults bioassay all concentrations tested reduced significantly the survival and reproduction of the insects. Thus is evidence that P. aduncum is a potential plant for stink bug control, because it had deleterious action in all development phases on E. heros. .

Esta pesquisa avaliou o potencial inseticida do extrato de folhas de Piper aduncum (L.) (Piperaceae) sobre o desenvolvimento do percevejo marrom, Euschistus heros (F.), a principal praga da soja no Mato Grosso. Para este estudo, foram realizados bioensaios com ovos, ninfas e adultos do percevejo, utilizando as concentrações de 0,5; 1,0; 2,0; 4,0 e 8,0%, do extrato acetônico de P. aduncum e como controle acetona P.A. Foram avaliados o número de ovos inviáveis, a mortalidade de ninfas e a longevidade, fecundidade e fertilidade dos adultos. No bioensaio de imersão dos ovos, todas as concentrações maiores que 1% tornou inviável mais de 70% dos ovos, enquanto, no bioensaio de contato, apenas 19% dos ovos foram inviabilizados na concentração 8%, diferindo do controle. No bioensaio com ninfas, as concentrações de 8% e 4% ocasionaram morte de 72% e 52%, respectivamente. No bioensaio com adultos, todas as concentrações testadas reduziram significativamente a sobrevivência dos insetos e a reprodução dos insetos. Assim, ficou evidente que P. aduncum é uma planta com potencial para o controle do percevejo marrom, pois teve ação deletéria em todas as fases de desenvolvimento de E. heros. .

RESUMO

Objetivou-se simular o número de gerações do percevejo Euschistus heros e seu parasitoide Telenomus podisi e da severidade da ferrugem causada por Phakopsora pachyrhizi na cultura da soja em função da data de semeadura, cultivar e momento de ocorrência desses organismos. A simulação foi feita em dois locais representativos de duas importantes regiões produtoras de soja no Estado do Rio Grande do Sul. Modelos bioclimáticos dos insetos e da doença foram integrados a um modelo de simulação da cultura da soja (DSSAT) e rodados para uma série temporal de dados meteorológicos diários para Passo Fundo (52 anos) e Santa Rosa (34 anos). Independente do grupo de maturação, quanto mais antecipada foi a data da semeadura e o estádio de ocorrência de E. heros na cultura, maior o número de gerações (de 2 a 3) até a maturação fisiológica da soja. Para T. podisi, um maior número de gerações (5 a 6) foi simulado para semeadura antecipada e cultivares de ciclo tardio. Para a ferrugem asiática não foram observadas tendências de redução nos níveis médios de severidade com o uso de práticas preconizadas, como plantio antecipado e cultivares de grupos mais precoces de maturação.

The objective of this study was to simulate the number of generations of a soybean insect pest (Euschistus heros) and its parasitoid (Telenomus podisi) and a fungal disease (soybean rust caused by Phakopsora pachyrhizi) as influenced by sowing date, cultivar and time of occurrence of the pest and the disease. Bioclimatic models that predict development of the organisms and severity of the disease were integrated into a crop simulation model of soybean (DSSAT) that predicted phenological stages of the crop for scenarios of sowing data and cultivar maturity group in a long time series of daily meteorological data to Passo Fundo and Santa Rosa, Rio Grande do Sul State, Brazil. The results showed that regardless of the maturity group, the earlier the sowing date and the time of occurrence of E. heros in the field, the greater its number of generations (2 to 3) until physiological maturity. For T. podisi, a higher number of generations (5 to 6) was estimated for the earlier sowing dates and late-maturing cultivars. For soybean rust no significant trends of reduction in the mean disease severity was observed when advocated practices such as early sowing and early-maturing cultivars were used.

RESUMO

The objective of this study was to evaluate the selectivity of alternative products to the egg parasitoid Telenomus podisi (Ashmead) (Hymenoptera: Scelionidae). The products used were Oil Geranium, Natualho®, Pironat®, Rotenat®, Natuneem® and Compostonat at the concentration recommended by manufacturer. Was sprayed 0.2 mL-1 of grout on cards containing 25 eggs of Euschistus heros (Fabricius) (Hemiptera: Pentatomidae) and sterile distilled water as a control. For the free-choice test, a female T. podisi was confined in a glass tube with two cards containing eggs of E. heros one being sprayed with treatment and other with sterile distilled water. . In the no-choice test, a female of T. podisi was confined ina a glass tube containing a card with eggs of E. heros, for a period of 24 h, the card being sprayed with the product prior or subsequent to parasitism. The parasitism percentage, emergence percentage, egg-adult period and sex ratio were evaluated. In free-choice test, the products Compostonat, Natualho® and Geranium Oil reduced significantly the percentage of parasitism. Similar reduction was also observed in no-choice test for Natualho® and Geranium oil in pre and post-parasitism. In pre-parasitism Compostonat and Geranium oil reduced the emergence and egg-adult period was affected by Natualho®. In post- parasitism there was a reduction in the number of eggs with signs of pa

O objetivo deste trabalho foi avaliar o efeito de produtos alternativos sobre o parasitoide de ovos Telenomus podisi (Ashmead) (Hymenoptera: Scelionidae). Os produtos utilizados foram Óleo de Gerânio, Natualho®, Pironat®, Rotenat®, Natuneem® e Compostonat, na concentração recomendada pelo fabricante. Foram pulverizados 0,2 mL das caldas sobre cartelas contendo 25 ovos de Euschistus heros (Fabricius) (Hemiptera: Pentatomidae) e, como testemunha água destilada esterilizada. Para o teste com chance de escolha, uma fêmea de T. podisi foi confinada em tubo de vidro, com duas cartelas contendo ovos de E. heros, sendo uma pulverizada com o tratamento e a outra com água destilada esterilizada. No teste sem chance de escolha, uma fêmea de T. podisi foi confinada em um tubo de vidro contendo uma cartela de ovos de E. heros, por um período de 24 h, sendo a cartela pulverizada com o produto previamente ou posteriormente ao parasitismo. Em ambos os experimentos avaliou-se a porcentagem de parasitismo, porcentagem de emergência de adulto dos parasitoides, período ovo-adulto e razão sexual. No teste com chance de escolha, os produtos Compostonat, Natualho® e Óleo de Gerânio reduziram significativamente a taxa de parasitismo. Redução semelhante também foi observada no teste sem chance de escolha para Natualho® e Óleo de Gerânio no pré e pós-parasitismo. No pré-parasitismo Compostonat e Óleo de

RESUMO

The objective of this study was to simulate the number of generations of a soybean insect pest (Euschistus heros) and its parasitoid (Telenomus podisi) and a fungal disease (soybean rust caused by Phakopsora pachyrhizi) as influenced by sowing date, cultivar and time of occurrence of the pest and the disease. Bioclimatic models that predict development of the organisms and severity of the disease were integrated into a crop simulation model of soybean (DSSAT) that predicted phenological stages of the crop for scenarios of sowing data and cultivar maturity group in a long time series of daily meteorological data to Passo Fundo and Santa Rosa, Rio Grande do Sul State, Brazil. The results showed that regardless of the maturity group, the earlier the sowing date and the time of occurrence of E. heros in the field, the greater its number of generations (2 to 3) until physiological maturity. For T. podisi, a higher number of generations (5 to 6) was estimated for the earlier sowing dates and late-maturing cultivars. For soybean rust no significant trends of reduction in the mean disease severity was observed when advocated practices such as early sowing and early-maturing cultivars were used.

Objetivou-se simular o número de gerações do percevejo Euschistus heros e seu parasitoide Telenomus podisi e da severidade da ferrugem causada por Phakopsora pachyrhizi na cultura da soja em função da data de semeadura, cultivar e momento de ocorrência desses organismos. A simulação foi feita em dois locais representativos de duas importantes regiões produtoras de soja no Estado do Rio Grande do Sul. Modelos bioclimáticos dos insetos e da doença foram integrados a um modelo de simulação da cultura da soja (DSSAT) e rodados para uma série temporal de dados meteorológicos diários para Passo Fundo (52 anos) e Santa Rosa (34 anos). Independente do grupo de maturação, quanto mais antecipada foi a data da semeadura e o estádio de ocorrência de E. heros na cultura, maior o número de gerações (de 2 a 3) até a maturação fisiológica da soja. Para T. podisi, um maior número de gerações (5 a 6) foi simulado para semeadura antecipada e cultivares de ciclo tardio. Para a ferrugem asiática não foram observadas tendências de redução nos níveis médios de severidade com o uso de práticas preconizadas, como plantio antecipado e cultivares de grupos mais precoces de maturação.

RESUMO

The objective of this study was to evaluate the selectivity of alternative products to the egg parasitoid Telenomus podisi (Ashmead) (Hymenoptera: Scelionidae). The products used were Oil Geranium, Natualho®, Pironat®, Rotenat®, Natuneem® and Compostonat at the concentration recommended by manufacturer. Was sprayed 0.2 mL-1 of grout on cards containing 25 eggs of Euschistus heros (Fabricius) (Hemiptera: Pentatomidae) and sterile distilled water as a control. For the free-choice test, a female T. podisi was confined in a glass tube with two cards containing eggs of E. heros one being sprayed with treatment and other with sterile distilled water. . In the no-choice test, a female of T. podisi was confined ina a glass tube containing a card with eggs of E. heros, for a period of 24 h, the card being sprayed with the product prior or subsequent to parasitism. The parasitism percentage, emergence percentage, egg-adult period and sex ratio were evaluated. In free-choice test, the products Compostonat, Natualho® and Geranium Oil reduced significantly the percentage of parasitism. Similar reduction was also observed in no-choice test for Natualho® and Geranium oil in pre and post-parasitism. In pre-parasitism Compostonat and Geranium oil reduced the emergence and egg-adult period was affected by Natualho®. In post- parasitism there was a reduction in the number of eggs with signs of pa

O objetivo deste trabalho foi avaliar o efeito de produtos alternativos sobre o parasitoide de ovos Telenomus podisi (Ashmead) (Hymenoptera: Scelionidae). Os produtos utilizados foram Óleo de Gerânio, Natualho®, Pironat®, Rotenat®, Natuneem® e Compostonat, na concentração recomendada pelo fabricante. Foram pulverizados 0,2 mL das caldas sobre cartelas contendo 25 ovos de Euschistus heros (Fabricius) (Hemiptera: Pentatomidae) e, como testemunha água destilada esterilizada. Para o teste com chance de escolha, uma fêmea de T. podisi foi confinada em tubo de vidro, com duas cartelas contendo ovos de E. heros, sendo uma pulverizada com o tratamento e a outra com água destilada esterilizada. No teste sem chance de escolha, uma fêmea de T. podisi foi confinada em um tubo de vidro contendo uma cartela de ovos de E. heros, por um período de 24 h, sendo a cartela pulverizada com o produto previamente ou posteriormente ao parasitismo. Em ambos os experimentos avaliou-se a porcentagem de parasitismo, porcentagem de emergência de adulto dos parasitoides, período ovo-adulto e razão sexual. No teste com chance de escolha, os produtos Compostonat, Natualho® e Óleo de Gerânio reduziram significativamente a taxa de parasitismo. Redução semelhante também foi observada no teste sem chance de escolha para Natualho® e Óleo de Gerânio no pré e pós-parasitismo. No pré-parasitismo Compostonat e Óleo de

RESUMO

The objective of this study was to simulate the number of generations of a soybean insect pest (Euschistus heros) and its parasitoid (Telenomus podisi) and a fungal disease (soybean rust caused by Phakopsora pachyrhizi) as influenced by sowing date, cultivar and time of occurrence of the pest and the disease. Bioclimatic models that predict development of the organisms and severity of the disease were integrated into a crop simulation model of soybean (DSSAT) that predicted phenological stages of the crop for scenarios of sowing data and cultivar maturity group in a long time series of daily meteorological data to Passo Fundo and Santa Rosa, Rio Grande do Sul State, Brazil. The results showed that regardless of the maturity group, the earlier the sowing date and the time of occurrence of E. heros in the field, the greater its number of generations (2 to 3) until physiological maturity. For T. podisi, a higher number of generations (5 to 6) was estimated for the earlier sowing dates and late-maturing cultivars. For soybean rust no significant trends of reduction in the mean disease severity was observed when advocated practices such as early sowing and early-maturing cultivars were used.

Objetivou-se simular o número de gerações do percevejo Euschistus heros e seu parasitoide Telenomus podisi e da severidade da ferrugem causada por Phakopsora pachyrhizi na cultura da soja em função da data de semeadura, cultivar e momento de ocorrência desses organismos. A simulação foi feita em dois locais representativos de duas importantes regiões produtoras de soja no Estado do Rio Grande do Sul. Modelos bioclimáticos dos insetos e da doença foram integrados a um modelo de simulação da cultura da soja (DSSAT) e rodados para uma série temporal de dados meteorológicos diários para Passo Fundo (52 anos) e Santa Rosa (34 anos). Independente do grupo de maturação, quanto mais antecipada foi a data da semeadura e o estádio de ocorrência de E. heros na cultura, maior o número de gerações (de 2 a 3) até a maturação fisiológica da soja. Para T. podisi, um maior número de gerações (5 a 6) foi simulado para semeadura antecipada e cultivares de ciclo tardio. Para a ferrugem asiática não foram observadas tendências de redução nos níveis médios de severidade com o uso de práticas preconizadas, como plantio antecipado e cultivares de grupos mais precoces de maturação.

RESUMO

Neste estudo, foram caracterizadas as injúrias causadas pelos percevejos Dichelops furcatus (F.), Nezara viridula (L.) e Euschistus heros (F.), em comparação com D. melacanthus (Dallas), em plântulas de milho (Zea mays L.). O experimento foi realizado em vasos, em ambiente de telado, em delineamento inteiramente casualizado, com cinco tratamentos (infestação com percevejos de quatro espécies e testemunha, sem infestação) em oito repetições. Na fase vegetativa do milho (estádio V1 até V3), D. melacanthus, na densidade de um adulto/planta, provocou redução na altura, no número de folhas expandidas, na massa seca das raízes e provocou injúrias no cartucho e/ou enrolamento das folhas centrais da planta. D. furcatus, E. heros e N. viridula causaram injúrias, porém, em intensidades diferentes. As injúrias causadas por D. furcatus e N. viridula foram semelhantes na forma e intensidade às de D. melacanthus e as injúrias causadas por E. heros foram menos intensas que as dos demais percevejos estudados.

Injuries caused by the stink bugs Dichelops furcatus (F.), Nezara viridula (L.) and Euschistus heros (F.), compared with Dichelops melacanthus (Dallas), to corn (Zea mays L.) seedlings were studied. The experiment was conducted in a greenhouse in a completely randomized design with five treatments (four species of stink bugs and control, without infestation) using eight replications. In the vegetative stage (V1 to V3) D. melacanthus, at the density of one adult/plant, caused reduction in height, in the number of expanded leaves, in root dry matter, and caused injuries and winding of the central leaves. D. furcatus, E. heros and N. viridula caused injuries, but at different intensities. Injuries caused by D. furcatus and N. viridula were similar in intensity to those by D. melacanthus and the injuries caused by E. heros were less intense than those of the other species.

RESUMO

Injuries caused by the stink bugs Dichelops furcatus (F.), Nezara viridula (L.) and Euschistus heros (F.), compared with Dichelops melacanthus (Dallas), to corn (Zea mays L.) seedlings were studied. The experiment was conducted in a greenhouse in a completely randomized design with five treatments (four species of stink bugs and control, without infestation) using eight replications. In the vegetative stage (V1 to V3) D. melacanthus, at the density of one adult/plant, caused reduction in height, in the number of expanded leaves, in root dry matter, and caused injuries and winding of the central leaves. D. furcatus, E. heros and N. viridula caused injuries, but at different intensities. Injuries caused by D. furcatus and N. viridula were similar in intensity to those by D. melacanthus and the injuries caused by E. heros were less intense than those of the other species.

Neste estudo, foram caracterizadas as injúrias causadas pelos percevejos Dichelops furcatus (F.), Nezara viridula (L.) e Euschistus heros (F.), em comparação com D. melacanthus (Dallas), em plântulas de milho (Zea mays L.). O experimento foi realizado em vasos, em ambiente de telado, em delineamento inteiramente casualizado, com cinco tratamentos (infestação com percevejos de quatro espécies e testemunha, sem infestação) em oito repetições. Na fase vegetativa do milho (estádio V1 até V3), D. melacanthus, na densidade de um adulto/planta, provocou redução na altura, no número de folhas expandidas, na massa seca das raízes e provocou injúrias no cartucho e/ou enrolamento das folhas centrais da planta. D. furcatus, E. heros e N. viridula causaram injúrias, porém, em intensidades diferentes. As injúrias causadas por D. furcatus e N. viridula foram semelhantes na forma e intensidade às de D. melacanthus e as injúrias causadas por E. heros foram menos intensas que as dos demais percevejos estudados.

RESUMO

Injuries caused by the stink bugs Dichelops furcatus (F.), Nezara viridula (L.) and Euschistus heros (F.), compared with Dichelops melacanthus (Dallas), to corn (Zea mays L.) seedlings were studied. The experiment was conducted in a greenhouse in a completely randomized design with five treatments (four species of stink bugs and control, without infestation) using eight replications. In the vegetative stage (V1 to V3) D. melacanthus, at the density of one adult/plant, caused reduction in height, in the number of expanded leaves, in root dry matter, and caused injuries and winding of the central leaves. D. furcatus, E. heros and N. viridula caused injuries, but at different intensities. Injuries caused by D. furcatus and N. viridula were similar in intensity to those by D. melacanthus and the injuries caused by E. heros were less intense than those of the other species.

Neste estudo, foram caracterizadas as injúrias causadas pelos percevejos Dichelops furcatus (F.), Nezara viridula (L.) e Euschistus heros (F.), em comparação com D. melacanthus (Dallas), em plântulas de milho (Zea mays L.). O experimento foi realizado em vasos, em ambiente de telado, em delineamento inteiramente casualizado, com cinco tratamentos (infestação com percevejos de quatro espécies e testemunha, sem infestação) em oito repetições. Na fase vegetativa do milho (estádio V1 até V3), D. melacanthus, na densidade de um adulto/planta, provocou redução na altura, no número de folhas expandidas, na massa seca das raízes e provocou injúrias no cartucho e/ou enrolamento das folhas centrais da planta. D. furcatus, E. heros e N. viridula causaram injúrias, porém, em intensidades diferentes. As injúrias causadas por D. furcatus e N. viridula foram semelhantes na forma e intensidade às de D. melacanthus e as injúrias causadas por E. heros foram menos intensas que as dos demais percevejos estudados.

RESUMO

Injuries caused by the stink bugs Dichelops furcatus (F.), Nezara viridula (L.) and Euschistus heros (F.), compared with Dichelops melacanthus (Dallas), to corn (Zea mays L.) seedlings were studied. The experiment was conducted in a greenhouse in a completely randomized design with five treatments (four species of stink bugs and control, without infestation) using eight replications. In the vegetative stage (V1 to V3) D. melacanthus, at the density of one adult/plant, caused reduction in height, in the number of expanded leaves, in root dry matter, and caused injuries and winding of the central leaves. D. furcatus, E. heros and N. viridula caused injuries, but at different intensities. Injuries caused by D. furcatus and N. viridula were similar in intensity to those by D. melacanthus and the injuries caused by E. heros were less intense than those of the other species.

Neste estudo, foram caracterizadas as injúrias causadas pelos percevejos Dichelops furcatus (F.), Nezara viridula (L.) e Euschistus heros (F.), em comparação com D. melacanthus (Dallas), em plântulas de milho (Zea mays L.). O experimento foi realizado em vasos, em ambiente de telado, em delineamento inteiramente casualizado, com cinco tratamentos (infestação com percevejos de quatro espécies e testemunha, sem infestação) em oito repetições. Na fase vegetativa do milho (estádio V1 até V3), D. melacanthus, na densidade de um adulto/planta, provocou redução na altura, no número de folhas expandidas, na massa seca das raízes e provocou injúrias no cartucho e/ou enrolamento das folhas centrais da planta. D. furcatus, E. heros e N. viridula causaram injúrias, porém, em intensidades diferentes. As injúrias causadas por D. furcatus e N. viridula foram semelhantes na forma e intensidade às de D. melacanthus e as injúrias causadas por E. heros foram menos intensas que as dos demais percevejos estudados.