RESUMO

Although the boll weevil (BW), Anthonomus grandis grandis (Coleoptera: Curculionidae) has been attributed to the significant losses caused to cotton yield in the Americas, the categorization as a quarentenary pest in places where it is still not occurring has increased its relevance worldwide. In areas where it is widespread, pest suppression relies on many broad-spectrum insecticide applications. However, other control tactics are sought. Considering that early-flowering cultivars escape from boll weevil infestation, we investigated if three different planting dates (November, December, and January) could alter the plant life cycle, allowing the plants to escape from boll weevil infestation. Field trials were run in two seasons (2014/2015 and 2017/2018), and variables (days required to reach each flowering stage, fruiting plant structures-undamaged and damaged by the BW, and totals-number of boll weevils on plants and that had emerged from fallen structures on the ground) were assessed over 29 and 33 weeks, respectively. Based on the number of days required to initiate and terminate the flowering stage, the time to reach the economic threshold (ET), the number of undamaged, damaged, and the total reproductive structures, we concluded that planting dates in December for the Central Cerrado of Brazil should be preferred over the other two tested dates. Cultivations run at this planting date, anticipating the flowering period initiation and termination, reduced infested flowering structures, and delayed the decision making to control the pest, when compared to the other two planting dates.

RESUMO

Huanglongbing (HLB), formerly known as greening, is a bacterial disease restricted to some Asian and African regions until two decades ago. Nowadays, associated bacteria and their vectors have spread to almost all citrus-producing regions, and it is currently considered the most devastating citrus disease. HLB management can be approached in terms of prevention, limiting or avoiding pathogen and associated vectors to reach an area, or in terms of control, trying to reduce the impact of the disease by adopting different cultural strategies depending on infestation/infection levels. In both cases, control of psyllid populations is currently the best way to stop HLB spread. Best cultural actions (CHMAs, TPS system) to attain this goal and, thus, able to limit HLB spread, and ongoing research in this regard is summarized in this review.

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RESUMO

The sugarcane aphid, Melanaphis sacchari (Zehntner) (Hemiptera: Aphididae), has become a major pest of grain sorghum, Sorghum bicolor (L.) Moench, in the United States in recent years. Feeding by large densities of sugarcane aphids causes severe damage, which can lead to a total loss of yield in extreme cases. Our objective was to determine the effect of grain sorghum planting date on sugarcane aphid population dynamics and their potential to reduce yields. We conducted field experiments from 2015 to 2017 in which an aphid-susceptible grain sorghum hybrid was planted at four different dates, which encompassed the typical range of planting dates used in Arkansas production systems. Plots were either protected from sugarcane aphid feeding using foliar insecticide sprays, or left untreated to allow natural populations of sugarcane aphids to colonize and reproduce freely. Planting date impacted both the magnitude and severity of sugarcane aphid infestations, with the highest population densities (and subsequent reductions in sorghum yield) generally occurring on plots that were planted in May or June. Sugarcane aphid feeding reduced yields in the untreated plots in two of the four planting date categories we tested. Earlier planting generally resulted in less sugarcane aphid damage and improved yields compared with later planting dates. While the effect of planting date on sugarcane aphid populations is likely to vary by region, sorghum producers should consider grain sorghum planting date as a potential cultural tactic to reduce the impact of sugarcane aphid.

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RESUMO

The invasive Mexican rice borer, Eoreuma loftini (Dyar), expanded its range from Mexico to South Texas in the early 1980s. By 2008 the pest had moved into sugarcane- and rice-growing areas of East Texas and Louisiana, and by 2012 it was reported on noncrop host plants in Florida. Efforts to suppress E. loftini in United States sugarcane with chemicals and biological control agents were unsuccessful, so both tactics were discontinued, and E. loftini infestation of sugarcane has continued unchecked. During the last 15 years, however, research has focused on the pest's ecology, improved insecticides and scouting methods, the identification of sugarcane resistance mechanisms, and new cultural tactics. A surveillance technique was developed that indicates when larvae are most vulnerable to insecticide sprays. Currently, registered insecticides for E. loftini control are not widely applied, although some show promise, including an insect growth regulator. A number of potentially useful cultural practices are available, including plowing under fallow stubble, judicious use of fertilizer, adequate irrigation, avoiding proximity to E. loftini-susceptible maize cultivars, and enhancement of natural enemy populations. Demonstrated and potentially useful sugarcane resistance mechanisms involve physiochemical attributes, physical characteristics, and transgenic cultivars.

RESUMO

Mexican bean beetle, Epilachna varivestis Mulsant, is a serious pest of snap beans, Phaseolus vulgaris L., in the eastern United States. These beetles are intolerant to direct sunlight, explaining why individuals are typically found on the undersides of leaves and in the lower portion of the plant canopy. We hypothesized that snap beans grown on reflective, agricultural polyethylene (plastic mulch) would have fewer Mexican bean beetles and less injury than those grown on black plastic or bare soil. In 2014 and 2015, beans were seeded into beds of metallized, white, and black plastic, and bare soil, in field plots near Blacksburg, VA. Mexican bean beetle density, feeding injury, predatory arthropods, and snap bean yield were sampled. Reflected light intensity, temperature, and humidity were monitored using data loggers. Pyranometer readings showed that reflected light intensity was highest over metallized plastic and second highest over white plastic; black plastic and bare soil were similarly low. Temperature and humidity were unaffected by treatments. Significant reductions in Mexican bean beetle densities and feeding injury were observed in both metallized and white plastic plots compared to black plastic and bare soil, with metallized plastic having the fewest Mexican bean beetle life stages and injury. Predatory arthropod densities were not reduced by reflective plastic. Metallized plots produced the highest yields, followed by white. The results of this study suggest that growing snap beans on reflective plastic mulch can suppress the incidence and damage of Mexican bean beetle, and increase yield in snap beans.

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RESUMO

Yellow sigatoka (Mycosphaerella musicola) is the main disease in banana areas in the Santa Catarina state. The objective of this research was to evaluate the effect of different methods of chemical and cultural control of sigatoka disease on Prata banana in subtropical climate. Six treatments were tested, evaluating three formulations (Tebuconazole 0,5 L ha-1 - Tiofanato metílico 0,6 L ha-1;  Citric biomass 1,0 L ha-1; water) with or without leaf removal. The variables evaluated were under the curve of progress (AUDPC) and final gross sum (GSfinal) area. The experimental design was randomized blocks in factorial scheme with five repetitions. Treatments were compared with Duncan´s test (P 0,05). Significant differences were verified for products compared to control, but not for leaf removal. It was found that fungicides and citric biomass resulted in significant reductions in AUDPC and GS final when compared to control. Fungicides and citric biomass reduced area under disease progress curve by 65 and 63%, as well as final gross sum were 87 and 73%, respectively. Results showed small influence of leaf removal, but new studies should evaluate its influence with higher frequency of defoliation. Fungicides and citric biomass are efficient in controlling sigatoka.(AU)

A sigatoka amarela (Mycosphaerella musicola) ainda é a principal doença da cultura da bananeira em Santa Catarina. Este trabalho teve como objetivo avaliar a eficiência de fungicidas e da desfolha no controle da Sigatoka em banana Prata. Foram testados seis tratamentos, combinando-se três formulações (Tebuconazole 0,5 L ha-1 - tiofanato metílico 0,6 L ha-1; Biomassa cítrica 1,0 L ha-1; água) com ou sem desfolha.  As variáveis avaliadas foram área abaixo da curva de progresso (AACPD) e soma bruta final (SBfinal) da doença. O delineamento experimental foi blocos ao acaso em esquema fatorial com cinco repetições, comparados entre si pelo teste de Duncan (P 0,05). Foram verificadas diferenças significativas para as formulações, mas não para desfolha, em comparação com testemunha. Para o fator formulação verificou-se que os fungicidas e a biomassa cítrica proporcionaram reduções significativas da área abaixo da curva de progresso da doença (AACPD) e soma bruta final (SBfinal) em comparação com testemunha. Os fungicidas e a biomassa cítrica reduziram a área abaixo da curva de progresso em 65 e 63%, assim como a soma bruta final caiu 83 e 73% em comparação com testemunha, respectivamente. Não se verificou influência da desfolha no controle da sigatoka, porém outros estudos com aplicações mais freqüentes devem ser realizados para quantificar melhor seu efeito. Concluiu-se que os fungicidas e a biomassa cítrica são eficientes no controle da sigatoka.(AU)

Assuntos

RESUMO

Yellow sigatoka (Mycosphaerella musicola) is the main disease in banana areas in the Santa Catarina state. The objective of this research was to evaluate the effect of different methods of chemical and cultural control of sigatoka disease on Prata banana in subtropical climate. Six treatments were tested, evaluating three formulations (Tebuconazole 0,5 L ha-1 - Tiofanato metílico 0,6 L ha-1;  Citric biomass 1,0 L ha-1; water) with or without leaf removal. The variables evaluated were under the curve of progress (AUDPC) and final gross sum (GSfinal) area. The experimental design was randomized blocks in factorial scheme with five repetitions. Treatments were compared with Duncan´s test (P 0,05). Significant differences were verified for products compared to control, but not for leaf removal. It was found that fungicides and citric biomass resulted in significant reductions in AUDPC and GS final when compared to control. Fungicides and citric biomass reduced area under disease progress curve by 65 and 63%, as well as final gross sum were 87 and 73%, respectively. Results showed small influence of leaf removal, but new studies should evaluate its influence with higher frequency of defoliation. Fungicides and citric biomass are efficient in controlling sigatoka.

A sigatoka amarela (Mycosphaerella musicola) ainda é a principal doença da cultura da bananeira em Santa Catarina. Este trabalho teve como objetivo avaliar a eficiência de fungicidas e da desfolha no controle da Sigatoka em banana Prata. Foram testados seis tratamentos, combinando-se três formulações (Tebuconazole 0,5 L ha-1 - tiofanato metílico 0,6 L ha-1; Biomassa cítrica 1,0 L ha-1; água) com ou sem desfolha.  As variáveis avaliadas foram área abaixo da curva de progresso (AACPD) e soma bruta final (SBfinal) da doença. O delineamento experimental foi blocos ao acaso em esquema fatorial com cinco repetições, comparados entre si pelo teste de Duncan (P 0,05). Foram verificadas diferenças significativas para as formulações, mas não para desfolha, em comparação com testemunha. Para o fator formulação verificou-se que os fungicidas e a biomassa cítrica proporcionaram reduções significativas da área abaixo da curva de progresso da doença (AACPD) e soma bruta final (SBfinal) em comparação com testemunha. Os fungicidas e a biomassa cítrica reduziram a área abaixo da curva de progresso em 65 e 63%, assim como a soma bruta final caiu 83 e 73% em comparação com testemunha, respectivamente. Não se verificou influência da desfolha no controle da sigatoka, porém outros estudos com aplicações mais freqüentes devem ser realizados para quantificar melhor seu efeito. Concluiu-se que os fungicidas e a biomassa cítrica são eficientes no controle da sigatoka.

Assuntos

RESUMO

Because boll weevil, Anthonomus grandis Boh. develops partially protected inside cotton fruiting structures, once they become established in a field, they are difficult to control, even with nearly continuous insecticide spray. During two cotton-growing seasons in the Semiárido region of Pernambuco State, Brazil, we tested the use of kaolin sprays to disrupt plant colonization through visual cue interference, combined with removal of fallen fruiting bodies to restrain boll weevil population growth after colonization. Kaolin spray under non-choice trials resulted in 2.2×, 4.4×, and 8.6× fewer weevils, oviposition and feeding punctures on kaolin-treated plants, respectively, despite demonstrating no statistical differences for colonization and population growth. Early season sprays in 2010 occurred during a period of rainfall, and hence, under our fixed spraying schedule no significant differences in boll weevil colonization were detected. In 2011, when kaolin sprays were not washed out by rain, delayed boll weevil colonization and reduction on attacked fruiting bodies were observed in eight out of 12 evaluations, and kaolin-treated plots had 2.7× fewer damaged fruiting bodies compared to untreated plots. Adoption of simple measures such as removal of fallen fruiting bodies and prompt reapplication of kaolin sprays after rainfall show promise in reducing boll weevil infestation.

RESUMO

Bemisia tabaci (Genn.) biotype B (Hemiptera: Aleyrodidae) is regarded as a pest with a large number of hosts, including crops and weeds. The performance of this whitefly on seven weeds was evaluated in order to identify the most suitable host. The following weeds that are very common in intense agricultural areas in the state of São Paulo, Brazil, were selected for this study: spurge (Euphorbia heterophylla), beggarticks (Bidens pilosa), red tasselflower (Emilia sonchifolia), small-flower galinsoga (Galinsoga parviflora), pigweed (Amaranthus viridis), black nightshade (Solanum americanum), and morning glory (Ipomoea sp.). In free-choice tests, adult preference and oviposition were greatest on spurge. In contrast, morning glory was the least attractive and least oviposited plant. In assays carried out for egg-adult development, egg viability was greater than 87% over all weeds, whereas nymph viability ranged from 74 to 97%. The developmental period from egg to adult ranged from 26.7 to 49.1 days among the hosts under study. The lowest nymph density rate was observed for beggarticks and morning glory. Cluster analysis resulted in a single group formed by spurge, indicating its superiority as a host for B. tabaci biotype B. Even though the parameters evaluated indicate that spurge is the most suitable host among the weeds, all the others allow the reproduction of B. tabaci biotype B. For this reason, they should be observed during cropping and the intercrop period in areas infested by this whitefly.

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RESUMO

Reniform nematode, cultural control, sustainable management.(AU)

In Brazil, the reniform nematode is a major disease problem of the cotton crop, causing damages of more than 60% in production. One management method aimed at reducing the damage caused by this nematode specie is the use of non-host plants that are used as soil improving crops. The objective of the present study was to evaluate the hospitability of species of soil improving crops to parasitism of Rotylenchulus reniformis. A total of 11 plant species used as soil improving crops were evaluated, along with cotton ‘CD 401 (Gossypium hirsutum) as a control of susceptibility. The statistical design was completely randomized with 10 replications. Among the 11 species evaluated, Stylosanthes ‘Campo Grande (Stylosantes capitata x S. macrocephala), Brachiaria ruziziensis, dwarf velvet bean (Mucuna deeringiana) sorghum ‘SI-3204 (Sorghum vulgare) and moha grass (Setaria italica) behaved as resistant. The corn ‘IPR115 (Zea mays), millet ‘BRS1501 (Pennisetum glaucum), and finger millet (Eleusine coracana) behaved as immune. However, the pigeon pea ‘IAPAR43 (Cajanus cajan) and pigeon pea ‘Fava Larga (C. cajan) behaved as susceptible, with an average number of eggs more than the control. Thus, it was concluded that the species Sorghum vulgare, Setaria italica, B. ruziziensis, M. deeringiana, Z. mays, P. glaucum, E. coracana and Stylosanthes Campo Grande, can be used as an option in the management of R. reniformis becoming a cost effective alternative for the producer, because it may decrease the population of this nematode.(AU)

Assuntos

RESUMO

Reniform nematode, cultural control, sustainable management.

In Brazil, the reniform nematode is a major disease problem of the cotton crop, causing damages of more than 60% in production. One management method aimed at reducing the damage caused by this nematode specie is the use of non-host plants that are used as soil improving crops. The objective of the present study was to evaluate the hospitability of species of soil improving crops to parasitism of Rotylenchulus reniformis. A total of 11 plant species used as soil improving crops were evaluated, along with cotton ‘CD 401’ (Gossypium hirsutum) as a control of susceptibility. The statistical design was completely randomized with 10 replications. Among the 11 species evaluated, Stylosanthes ‘Campo Grande’ (Stylosantes capitata x S. macrocephala), Brachiaria ruziziensis, dwarf velvet bean (Mucuna deeringiana) sorghum ‘SI-3204’ (Sorghum vulgare) and moha grass (Setaria italica) behaved as resistant. The corn ‘IPR115’ (Zea mays), millet ‘BRS1501’ (Pennisetum glaucum), and finger millet (Eleusine coracana) behaved as immune. However, the pigeon pea ‘IAPAR43’ (Cajanus cajan) and pigeon pea ‘Fava Larga’ (C. cajan) behaved as susceptible, with an average number of eggs more than the control. Thus, it was concluded that the species Sorghum vulgare, Setaria italica, B. ruziziensis, M. deeringiana, Z. mays, P. glaucum, E. coracana and Stylosanthes Campo Grande, can be used as an option in the management of R. reniformis becoming a cost effective alternative for the producer, because it may decrease the population of this nematode.

Assuntos

RESUMO

In Brazil, the reniform nematode is a major disease problem of the cotton crop, causing damages of more than 60% in production. One management method aimed at reducing the damage caused by this nematode specie is the use of non-host plants that are used as soil improving crops. The objective of the present study was to evaluate the hospitability of species of soil improving crops to parasitism of Rotylenchulus reniformis. A total of 11 plant species used as soil improving crops were evaluated, along with cotton 'CD 401' (Gossypium hirsutum) as a control of susceptibility. The statistical design was completely randomized with 10 replications. Among the 11 species evaluated, Stylosanthes 'Campo Grande' (Stylosantes capitata x S. macrocephala), Brachiaria ruziziensis, dwarf velvet bean (Mucuna deeringiana) sorghum 'SI-3204' (Sorghum vulgare) and moha grass (Setaria italica) behaved as resistant. The corn 'IPR115' (Zea mays), millet 'BRS1501' (Pennisetum glaucum), and finger millet (Eleusine coracana) behaved as immune. However, the pigeon pea 'IAPAR43' (Cajanus cajan) and pigeon pea 'Fava Larga' (C. cajan) behaved as susceptible, with an average number of eggs more than the control. Thus, it was concluded that the species Sorghum vulgare, Setaria italica, B. ruziziensis, M. deeringiana, Z. mays, P. glaucum, E. coracana and Stylosanthes Campo Grande, can be used as an option in the management of R. reniformis becoming a cost effective alternative for the producer, because it may decrease the population of this nematode.

No Brasil, o nematoide reniforme é um dos principais problemas fitossanitários da cultura do algodoeiro, podendo ocasionar perdas superiores a 60% na produção. Uma forma de manejo que tem sido apontada como uma prática na redução dos danos causados por este nematoide é o uso de espécies de plantas não hospedeiras que são utilizadas como plantas melhoradoras de solo e em rotação de culturas. O objetivo do trabalho foi avaliar a hospedabilidade de espécies de plantas melhoradoras de solo ao parasitismo de Rotylenchulus renfiormis. Foram avaliadas 11 espécies de plantas melhoradoras de solo e como testemunha de suscetibilidade utilizou-se o cultivar de algodão 'CD 401' (Gossypium hirsuturm). O delineamento estatístico utilizado foi o inteiramente casualizado com 10 repetições. Baseado nos fatores de reprodução, o estilosante 'Campo Grande' (Stylosantes capitata x S. macrocephala), a Brachiaria ruziziensis, a mucuna anã (Mucuna deeringiana), o sorgo 'SI-3204' (Sorghum vulgare) e o capim moha (Setaria italica) comportaram-se como resistentes; já o milho 'IPR115' (Zea mays), o milheto 'BRS1501' (Pennisetum glaucum) e o capim pé de galinha gigante (Eleusine coracana) como imunes. No entanto, o guandu anão 'IAPAR43' (Cajanus cajan) e o guandu 'Fava Larga' (C. cajan) comportaram-se como suscetíveis, com médias de número de ovos maiores que a testemunha. De acordo com os resultados conclui-se que as espécies S. vulgare, S. italica, B. ruziziensis, M. deerringiana, Z. mays, P. glaucum, E. coracana e Stylosanthes Campo Grande podem ser utilizadas como uma opção no manejo de R. reniformis, tornando-se uma alternativa rentável para o produtor, pois poderá diminuir a população desse nematoide.

RESUMO

Algumas publicações relatam que o adensamento populacional dos bananais reduz a severidade da sigatoka-negra (Mycosphaerella fijiensis). Instalou-se um ensaio com cinco tratamentos e quatro repetições. Os tratamentos 1.600, 2.000, 2.400, 2.800 e 3.200 plantas.ha-1 da cultivar D'Angola foram instalados em parcelas agrupadas de 2.000 m² cada. O tamanho das parcelas foi fixo e o número de plantas por parcela variou conforme o espaçamento adotado para cada população. A área de 2.000 m² foi dividida em quatro subáreas de 500 m², considerando-as como parcelas. Em cada subárea selecionaram-se 15 plantas centrais para serem avaliadas. Na época do florescimento registraram-se a severidade da doença na folha n.°10 e o número de folhas viáveis. Na colheita, a altura e o diâmetro do pseudocaule e o peso dos cachos, das pencas e dos frutos. A análise conjunta dos dados indica que todos os tratamentos foram semelhantes entre si e que o adensamento das plantas não controlou a sigatoka-negra.

Many publications show that plantations of high density of bananas decrease the severity of black-sigatoka (Mycosphaerella fijiensis). To test this hypothesis it was instaled an experiment with five treatments and four repetitions. The treatments were density plant of 1.600, 2.000, 2.400, 2.800 e 3.200 plant.ha-1. The cultivar planted was D'Angola and each plot had fixed 2.000 m², the number of plants in each plot changed in accordance with the treatment tested. The plots were divided in four subplots of 500 m² where 15 plants located in the center were measured. The evaluation of severity was carried out in the leaf number ten during the flowering period. It was also evaluated the numbers of viable leaves, height, diameter and weight of production (banch, bunches and fruits). The analyses did not show effect of high density in the parameter measured and it was conclued that the treatments tested had not control black-sigatoka.

Assuntos

RESUMO

Many publications show that plantations of high density of bananas decrease the severity of black-sigatoka (Mycosphaerella fijiensis). To test this hypothesis it was instaled an experiment with five treatments and four repetitions. The treatments were density plant of 1.600, 2.000, 2.400, 2.800 e 3.200 plant.ha-1. The cultivar planted was D'Angola and each plot had fixed 2.000 m², the number of plants in each plot changed in accordance with the treatment tested. The plots were divided in four subplots of 500 m² where 15 plants located in the center were measured. The evaluation of severity was carried out in the leaf number ten during the flowering period. It was also evaluated the numbers of viable leaves, height, diameter and weight of production (banch, bunches and fruits). The analyses did not show effect of high density in the parameter measured and it was conclued that the treatments tested had not control black-sigatoka.

Algumas publicações relatam que o adensamento populacional dos bananais reduz a severidade da sigatoka-negra (Mycosphaerella fijiensis). Instalou-se um ensaio com cinco tratamentos e quatro repetições. Os tratamentos 1.600, 2.000, 2.400, 2.800 e 3.200 plantas.ha-1 da cultivar D'Angola foram instalados em parcelas agrupadas de 2.000 m² cada. O tamanho das parcelas foi fixo e o número de plantas por parcela variou conforme o espaçamento adotado para cada população. A área de 2.000 m² foi dividida em quatro subáreas de 500 m², considerando-as como parcelas. Em cada subárea selecionaram-se 15 plantas centrais para serem avaliadas. Na época do florescimento registraram-se a severidade da doença na folha n.°10 e o número de folhas viáveis. Na colheita, a altura e o diâmetro do pseudocaule e o peso dos cachos, das pencas e dos frutos. A análise conjunta dos dados indica que todos os tratamentos foram semelhantes entre si e que o adensamento das plantas não controlou a sigatoka-negra.

RESUMO

The effect of fruit thinning on apple leafroller Bonagota cranaodes (Meyrick, 1937) (Lepidoptera: Tortricidae) damage was evaluated in commercial orchards of Fuji and Gala cultivars. At harvest, appies produced in clusters of two, three or four fruits and isolated ones were evaluated for percentage of pest damage. A positive correlation between lhe number of fruits per cluster and percentage of appie leafroller damage was observed. The injury to fruits was higher during late season cultivar Fuji (harvested in April) than early season Gala (February). Fruits produced in isolated floral buds were significativelly less damaged by the pest than in cluster, indicating that is possible Io use apple thinning to reduce apple leafroller damage in commercial orchards.

O efeito do rateio de frutos de maça sobre o dano provocado pela tagarta-enroladeira Bonagota cranaodes (Meyrick, 1937) (Lepidoptera: Tortricidae) foi avaliado em pomares comercias das cultivares Gala e Fuji, em Vacaria, RS. Na colheita, através de amostragem, foi registrada a porcentagem de maçãs danificadas, quando produzidas deforma isolada, e daquelas provenientes de cachopas florais formadas por dois, três e quatro frutos. Observou-se uma correlação positiva entre o número de frutos por cacho floral e a porcentagem de maçãs danificadas pelo inseto. Devido ao fato de que a cultivar Gala é mais precoce (colheita em fevereiro), o dano médio observado foi significativamente inferior ao da Fuji, cuja colheita é mais tardia (abril). Frutos produzidos de forma isolada nos ramos florais foram significativamente menos danificados pela praga, indicando, através do rateio de frutos, ser possível reduzir os prejuízos causados pela lagarta-enroladeira nos pomares de macieira.

RESUMO

The effect of fruit thinning on apple leafroller Bonagota cranaodes (Meyrick, 1937) (Lepidoptera: Tortricidae) damage was evaluated in commercial orchards of Fuji and Gala cultivars. At harvest, appies produced in clusters of two, three or four fruits and isolated ones were evaluated for percentage of pest damage. A positive correlation between lhe number of fruits per cluster and percentage of appie leafroller damage was observed. The injury to fruits was higher during late season cultivar Fuji (harvested in April) than early season Gala (February). Fruits produced in isolated floral buds were significativelly less damaged by the pest than in cluster, indicating that is possible Io use apple thinning to reduce apple leafroller damage in commercial orchards.

O efeito do rateio de frutos de maça sobre o dano provocado pela tagarta-enroladeira Bonagota cranaodes (Meyrick, 1937) (Lepidoptera: Tortricidae) foi avaliado em pomares comercias das cultivares Gala e Fuji, em Vacaria, RS. Na colheita, através de amostragem, foi registrada a porcentagem de maçãs danificadas, quando produzidas deforma isolada, e daquelas provenientes de cachopas florais formadas por dois, três e quatro frutos. Observou-se uma correlação positiva entre o número de frutos por cacho floral e a porcentagem de maçãs danificadas pelo inseto. Devido ao fato de que a cultivar Gala é mais precoce (colheita em fevereiro), o dano médio observado foi significativamente inferior ao da Fuji, cuja colheita é mais tardia (abril). Frutos produzidos de forma isolada nos ramos florais foram significativamente menos danificados pela praga, indicando, através do rateio de frutos, ser possível reduzir os prejuízos causados pela lagarta-enroladeira nos pomares de macieira.

RESUMO

Sternechus subsignatus (Boheman) is a curculionid occurring in some fields of the traditional soybean production área in southern Brazil. During the 1990/91 growing season, in Cruz A1ta - RS, in an Oxissol (Dark-Red Latossol), clay texture, after four years of soybean cultivation under no-till. the effect of the following soi1 tillage methods on the insect infestation and damage were evaluated: T1) NT = no-till. T2) CT + NT = conventional tillage in July and no-till after October; T3) N T + CT = no-till until July and conventional tillage after October; T4) CT = conventional tillage in July and October. Results demonstrated that the soil tillage methods influenced the establishment and activity of S. subsignatus and, in consequence, the productivity of soybean plants decreased in the soil under no-till and increased in the soil under conventional tillage (plowed and disk arrowed).

Sternechus subsignatus (Boheman) é um curculinídeo que ocorre em algumas lavouras da região tradicional de cultivo da soja no Bras1 (RS, SC e PR). Durante a safra de 1990/91 em Cruz Alta - RS, num Latossolo Vermelho Escuro distrófico, textura argilosa, com 4 anos de semeadura direta de soja avaliou-se o efeito dos seguintes métodos de preparo do solo na infestação e no dano deste inseto T1) PD = plantio direto T2) PC + PD = plantio convencional em julho e plantio direto a partir de outubro; T3) PD + PC = plantio direto até julho e plantio convencional a partir de outubro; T4 PC = plantio convencional em julho e outubro. Os resultados mostraram que os métodos de preparo do solo influenciaram o estabelecimento e a atividade de S. subsignatus e, conseqüentemente, a produtividade das plantas de soja, a qual é diminuída no solo preparado com plantio direto e aumentada no solo com arado e grade.

RESUMO

Sternechus subsignatus (Boheman) is a curculionid occurring in some fields of the traditional soybean production área in southern Brazil. During the 1990/91 growing season, in Cruz A1ta - RS, in an Oxissol (Dark-Red Latossol), clay texture, after four years of soybean cultivation under no-till. the effect of the following soi1 tillage methods on the insect infestation and damage were evaluated: T1) NT = no-till. T2) CT + NT = conventional tillage in July and no-till after October; T3) N T + CT = no-till until July and conventional tillage after October; T4) CT = conventional tillage in July and October. Results demonstrated that the soil tillage methods influenced the establishment and activity of S. subsignatus and, in consequence, the productivity of soybean plants decreased in the soil under no-till and increased in the soil under conventional tillage (plowed and disk arrowed).

Sternechus subsignatus (Boheman) é um curculinídeo que ocorre em algumas lavouras da região tradicional de cultivo da soja no Bras1 (RS, SC e PR). Durante a safra de 1990/91 em Cruz Alta - RS, num Latossolo Vermelho Escuro distrófico, textura argilosa, com 4 anos de semeadura direta de soja avaliou-se o efeito dos seguintes métodos de preparo do solo na infestação e no dano deste inseto T1) PD = plantio direto T2) PC + PD = plantio convencional em julho e plantio direto a partir de outubro; T3) PD + PC = plantio direto até julho e plantio convencional a partir de outubro; T4 PC = plantio convencional em julho e outubro. Os resultados mostraram que os métodos de preparo do solo influenciaram o estabelecimento e a atividade de S. subsignatus e, conseqüentemente, a produtividade das plantas de soja, a qual é diminuída no solo preparado com plantio direto e aumentada no solo com arado e grade.

RESUMO

Avaliou-se, a campo, a influência da rotação de culturas com milho e soja na infestação e nos danos causados pelo tamanduâ-da-soja, Sternechus subsignatus (Boheman, 1836), em solos manejados no sistema de plantio direto. no município de Cruz Alta, RS. Os resultados indicaram que a infestação de adultos, larvas olivas e larvas hibernantes e os danos de percentagem de plantas de soja atacadas e mortas foram significativamente inferiores na rotação com milho e soja do que o verificado no monocultivo de soja. A soja em rotação com o milho produziu significativamente mais grãos do que a soja em monocultivo. Concluiu-se que a rotação com milho e soja constitui-se numa prática importante a ser usada no manejo de S. subsignatus em áreas infestadas, pelo fato do inseto não se alimentar e nem ovipositar nas plantas de milho, o que propicia a diminuição da sua população.

The corn and soybean crop rotation on Sternechus subsignatus (Boheman. 1836) infestation and damage under notillage was evaluated in the field in the county of Cruz Alta, Rio Grande do Sul State. Brazil. The results indicated that adult infestation. active larvae and hibernating larvae, and that the percent damage of soybean plants attacked and dead, were significantiy lower in the corn-soybean crop rotation in relation to soybean under monocultural system. Soybean in rotation with corn showes significant more grain productivity than soybean under monocultural system. It was concluded that the corn-soybean rotation is an important tool for the management of S. subsignatus in infested areas due to the fact that the insect neither feed nor perform oviposition on corn plants, thus reducing its population.

RESUMO

The corn and soybean crop rotation on Sternechus subsignatus (Boheman. 1836) infestation and damage under notillage was evaluated in the field in the county of Cruz Alta, Rio Grande do Sul State. Brazil. The results indicated that adult infestation. active larvae and hibernating larvae, and that the percent damage of soybean plants attacked and dead, were significantiy lower in the corn-soybean crop rotation in relation to soybean under monocultural system. Soybean in rotation with corn showes significant more grain productivity than soybean under monocultural system. It was concluded that the corn-soybean rotation is an important tool for the management of S. subsignatus in infested areas due to the fact that the insect neither feed nor perform oviposition on corn plants, thus reducing its population.

Avaliou-se, a campo, a influência da rotação de culturas com milho e soja na infestação e nos danos causados pelo tamanduâ-da-soja, Sternechus subsignatus (Boheman, 1836), em solos manejados no sistema de plantio direto. no município de Cruz Alta, RS. Os resultados indicaram que a infestação de adultos, larvas olivas e larvas hibernantes e os danos de percentagem de plantas de soja atacadas e mortas foram significativamente inferiores na rotação com milho e soja do que o verificado no monocultivo de soja. A soja em rotação com o milho produziu significativamente mais grãos do que a soja em monocultivo. Concluiu-se que a rotação com milho e soja constitui-se numa prática importante a ser usada no manejo de S. subsignatus em áreas infestadas, pelo fato do inseto não se alimentar e nem ovipositar nas plantas de milho, o que propicia a diminuição da sua população.