Diversidade de pulgões e de seus parasitóides e predadores na cultura da alfafa

O objetivo deste trabalho foi verificar a diversidade de pulgões, seus predadores e parasitóides, e a influência de fatores climáticos nas suas populações. Foram realizadas coletas semanais no período de abril/1995 a março/1996, no campo de alfafa da Universidade Federal de Lavras (UFLA), em Lavras, MG. As espécies de pulgões coletadas foram Therioaphis trifolii (Monel) f. maculata, Acyrthosiphon pisum (Harris), A. kondoi Shinji e Aphis craccivora Kock, presentes na cultura durante todo o período de estudo, com picos populacionais em novembro/1995, julho/1995, dezembro/1995 e abril/1996, respectivamente. Foram amostrados insetos predadores das famílias Coccinellidae, Syrphidae, Anthocoridae, Geocoridae e Chrysopidae, tendo as duas últimas ocorrência esporádica. Espécies da família Coccinellidae ocorreram durante todo o período amostral, apresentando o pico populacional no final de dezembro/1995, com precipitação de 20 mm e temperatura de 22,6ºC. A família Syrphidae alcançou maiores números em abril, à precipitação de 53 mm e temperatura de 21ºC. A família Anthocoridae não se manteve por todo o período amostral, porém um pico populacional ocorreu no final de dezembro nas mesmas condições que aquele apresentado pela família Coccinellidae. Os parasitóides da família Aphididae alcançaram pico em junho/1995, à temperatura de 16ºC.

Estimativa de Trichogramma pretiosum para controle de Tuta absoluta em tomateiro estaqueado

O objetivo deste trabalho foi estimar o número ideal de Trichogramma pretiosum Riley a ser liberado em campo para o controle da traça-do-tomateiro Tuta absoluta (Meyrick). O experimento foi implantado em casa de vegetação, onde, 60 dias após o transplantio, plantas de tomate foram infestadas com 200 ovos do hospedeiro alternativo Anagasta kuehniella (Zeller), na proporção de 70% no terço superior das plantas, 24% no terço médio e 6% no terço inferior. Fêmeas de T. pretiosum foram liberadas nas proporções de 1, 2, 4, 8, 16 e 32 parasitóides por ovo do hospedeiro. Independentemente do terço da planta analisado, a proporção de 16 parasitóides por ovo apresentou os melhores resultados. Esta é a proporção mais próxima da ideal, para liberação em plantios comerciais de tomate estaqueado, visando o controle da traça-do-tomateiro.

Mortalidade dos parasitóides Spilochalcis morleyi (Hymenoptera, Chalcididae) e Xanthozona melanopyga (Diptera, Tachinidae) em pupas femininas e masculinas de Brassolis sophorae (Lepidoptera, Nymphalidae)

Comparou-se o número médio de adultos emergidos, número de imaturos mortos e a freqüência com que ocorre a morte de toda a prole nos parasitóides Spilochalcis morleyi (Hymenoptera, Chalcididae) e Xanthozona melanopyga no hospedeiro, Brassolis sophorae (Lepidoptera, Nymphalidae). O número de parasitóides (Spilochalcis) que completaram seu desenvolvimento e emergiram foi significativamente maior em pupas femininas do hospedeiro. O número médio de imaturos de Spilochalcis mortos por pupa não diferiu entre os sexos do hospedeiro. Entretanto, nas pupas femininas de B. sophorae ocorreu uma freqüência significativamente maior de morte de toda a prole em ambas as espécies de parasitóides.

PREVISÃO da EMERGÊNCIA DE Trissolcus brochymenae (ASHMEAD) E Telenomus podisi ASHMEAD (HYMENOPTERA: SCELIONIDAE) EMCONDIÇÕES DE CAMPO

Procurou-se averiguar em condições de campo, a previsão da emergência de Trissolcus brochymenae (Ashmead) e Telenomus podisi Ashmead, parasitóides de ovos de Piezodorus guildinii (West.), usando um método baseado em graus-dia. A emergência total de adultos ocorreu depois que foram acumulados 211,2 graus-dia para T. brochymenae e 229 graus-dia para T. podisi . A precisão da previsão da emergência de mais de 50% de T. brochymenae foi melhor que a de T. podisi, e para ambas as espécies esta emergência ocorreu a 2-3 dias da data prevista.

Manipulation of fire ant density, Solenopsis spp., for short-term reduction of Diatraea saccharalis larval densities in Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Short-term assessment of bt maize on non-target arthropods in Brazil

Embora não haja cultivos comerciais de milho geneticamente modificado no Brasil, o efeito de híbridos de milho Bt sobre inimigos naturais e artrópodos de solo deve ser avaliado antes da liberação aos produtores. Assim, ensaios foram conduzidos durante uma safra em duas localidades. Os híbridos de milho modificado geneticamente 7590-Bt11 e Avant-ICP4 foram comparados com seus respectivos isogênicos não transgênicos. Os artrópodes foram avaliados através de observação direta nas plantas e armadilhas de alçapão. de modo geral, não se observaram diferenças entre as populações de tesourinha (Dermaptera: Forficulidae), joaninhas (Coleptera: Coccinellidae), percevejo-pirata (Coleoptera: Anthocoridae), carabídeos (Carabidae), cicindelídeos (Cicindelidae) e aranhas (Araneae). Também não houve diferença no parasitismo de ovos de Helicoverpa zea (Boddie) por Trichogramma sp. (Hymenoptera: Trichogrammatidae). Assim, milho geneticamente modificado expressando as proteínas inseticidas Cry1A(b) e VIP 3A não causa redução nas populações dos principais predadores e parasitóides.

Marigold (Tagetes erecta L.) as an attractive crop to natural enemies in onion fields

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Parasitismo em lagarta-do-cartucho, Spodoptera frugiperda (Smith), na região do Triângulo Mineiro, MG

Com o objetivo de avaliar a freqüência e distribuição de parasitóides associados a larvas da lagarta do cartucho, Spodoptera frugiperda (Smith), foram realizadas amostragens em campos comerciais da cultura do milho (Zea mays), nos anos agrícolas 1991/92 (duas regiões) e 1992/93 (cinco regiões). em cada local amostrado foram coletadas aproximadamente 100 larvas, em plantas com 20 a 40 dias após a emergência. As larvas foram criadas em laboratório a 25 ± 2ºC, UR 50 - 60%, fotoperíodo de 14 horas e observadas diariamente. Os parasitóides mais freqüentes foram: Chelonus texanus (Cresson) (Hymenoptera: Braconidae), Diadegma sp. (Hymenoptera: Ichneumonidae) e Archytas incertus (Macquart) (Diptera: Tachinidae). Foi observado que o parasitismo total foi de 10,3% em 1991/92 e 13,8% em 1992/93. Os parasitóides Diptera apresentaram preferência pela fase de pupa da lagarta do cartucho (76,5%), nos dois anos agrícolas. Os parasitóides Hymenoptera tiveram preferência por larvas de 3º e 4º ínstares (41,9 e 45,2%), no ano agrícola 1991/92 e de 2º e 3º ínstares (39,1 e 43,5%), no ano agrícola 1992/93.

Insecticide selectivity to two species of Trichogramma in three different hosts, as determined by IOBC/WPRS methodology

BACKGROUND: The use of Trichogramma species is a potential key strategy in integrated pest management. However, its effectiveness depends on the use of chemicals that do not interfere with parasitism and parasite population growth. Here, a study was made of the effects of synthetic insecticides on Trichogramma pretiosum and Trichogramma exiguum in different hosts (Ephestia kuehniella, Plutella xylostella and Spodoptera frugiperda) and the influence of International Organisation for Biological Control (IOBC/WPRS) methodology in selectivity studies using different Trichogramma species. The insecticides used were commercial formulations (triflumuron at a concentration of 0.2 mL L-1 water, etofenprox at a concentration of 0.47 mL L-1 water and endosulfan at a concentration of 7.5 mL L-1 water); the control treatment consisted of distilled water. Eggs attached to cardboard cards were offered to parasitoids inside glass cages. Parasitised eggs, parasitism and adult emergence rates and parasitism reduction were evaluated.RESULTS: Endosulfan and etofenprox, classified as class-4 toxic products, were extremely toxic to the parasitoids. Triflumuron, classified as a non-toxic product, was selective to the parasitoids in eggs of all hosts.CONCLUSIONS: The methodology recommended by IOBC/WPRS influenced results regarding the use of different species of parasitoids, and the use of a single parasitoid species in their experiment is questionable. (C) 2011 Society of Chemical Industry

Efeitos dos inseticidas utilizados no controle de Bemisia tabaci (Gennadius) biótipo B e sua seletividade aos inimigos naturais na cultura da soja

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.

Use of Rubidium to Label Lysiphlebus testaceipes (Hymenoptera: Braconidae), a Parasitoid of Greenbugs (Homoptera: Aphididae), for Dispersal Studies

A reliable method of labeling is needed to study dispersal of the braconid parasitoid, Lysiphlebus testaceipes (Cresson), an important biological control of greenbugs, Schizaphis graminum (Rondani), on grain sorghum, Sorghum bicolor (L.) Moench. The feasibility of using aqueous solutions of rubidium chloride (RbCl) applied as a foliar spray or soil drench to label greenbugs and L. testaceipes developing within greenbugs was studied. Laboratory and field studies were conducted to identify the minimal concentration of RbCl to assure labeling of greenbugs and wasps, persistence of Rb throughout the wasp's life span, mobility of Rb to unsprayed sorghum leaves, and feasibility of studying dispersal using a release-recapture technique with Rb-labeled wasps. Both greenbugs and wasps could be labeled using RbCl at concentrations of 2,500-10,000 ppm. Rubidium content in labeled wasps did not significantly vary during the first 7 d after emergence. Greenbugs feeding on unsprayed leaves were labeled up to 4 wk after leaves were sprayed. Rb-labeled wasps were found at the maximum trap distance from the release site (60 m) within 1 d after release.

Parasitism of Greenbugs (Homoptera: Aphididae) by Lysiphlebus testaceipes (Hymenoptera: Braconidae) in Grain Sorghum: Implications for Augmentative Biological Control

Field cage studies were conducted to describe the relationship between the percentage of Lysiphlebus testaceipes (Cresson) parasitism (as measured by aphid mummies) and densities of greenbug, Schizaphis graminum Rondani, on grain sorghum, Sorghum bicolor L. In 1993 and 1994, a biotype E-susceptible grain sorghum hybrid was grown in field cages and L. testaceipes adults were released after each plant was infested with 20 biotype E greenbugs. The release rates were 0, 0.5, 1.0, and 2.0 wasps per plant in 1993, and 0, 0.16, 0.33, and 0.5 wasps per plant in 1994. Greenbugs and mummies were counted 1-2 times a week on all leaves of 2-4 randomly selected plants per cage. A release rate of 0.33-0.5 wasps per plant infested with 20 greenbugs maximized the number of mummies produced and prevented the greenbugs from reaching an economic threshold of 1,000 greenbugs per plant. Peak numbers of mummies occurred ≈400-500 DD (10°C base) after the initial wasp release. Regression analyses showed that the greenbug population started decreasing when the percentage of parasitism (as measured by mummies) reached 20-30 %. Greenbugs in the absence of wasps significantly reduced yield in 1994, but not in 1993.

Spatial pattern of parasitism in Diatraea saccharalis Fab. (Lep., Crambidae) populations at two different spatial scales in sugarcane fields in Brazil

The biological control of Diatraea saccharalis is regarded as one of the best examples of successful classical biological control in Brazil. Since the introduction of the exotic parasitoid, Cotesia flavipes, the decrease in D. saccharalis infestation in sugarcane fields has been attributed to the effectiveness of this agent. Native Tachinidae fly parasitoids (Lydella minense and Paratheresia claripalpis) have also been implicated in the success. Quantitative data confirming the actual contribution of these agents to the control of D. saccharalis are, however, rather scant. The purpose of this study was to investigate the spatial pattern of parasitism of these parasitoids in D. saccharalis populations at two large spatial scales (fields and zones). To investigate this subject, a large data set comprising information collected from a sugarcane mill located in the state of São Paulo, Brazil (São João sugarcane mill) was analysed. When regressions between the proportion parasitism against host density were computed, the percentage of significant regressions with either a positive or a negative slope was very small at both spatial scales for both parasitoid species. Regressing the densities of tachinid-parasitized hosts against host densities per field showed that these parasitoids presented a 'moderate aggregative' response to host densities, as 53.33% of the regressions were positively significant. Cotesia flavipes was 'weakly aggregated' on host densities at the field level, because only 33.33% of the regressions were positively significant. At the zone level, neither aggregative nor spatial proportion parasitism responses were evident for either parasitoid species due to the small percentage of significant regressions computed.

Fenologia e artrópodes de Copaifera langsdorffii Desf. no cerrado

There was evaluated the phenology and arthropods as well as the effect of weather on copaiba (Copaifera langsdorffii Desf.) (Leguminoseae). The emission of new leaves and inflorescences as well as the opening of them occurred in the rainy period. There were observed the higher diversity and abundance of insects, principally galling insects.

A preliminary investigation of pre-dispersal seed predation by Acanthoscelides schrankiae horn (Coleoptera: Bruchidae) in Mimosa bimucronata (DC.) Kuntze trees

This is the first record of Acanthoscelides schrankiae Horn, feeding in seeds of Mimosa bimucronata (DC.) Kuntze. We investigated the pattern of oviposition and seed exploitation by A. schrankiae, and the distribution of mature fruits and seed predation in the inflorescences. We also compared the percentage of predated seeds, the total dry weight of fruits and non-predated seeds, the percentage of aborted seeds, and the percentage of non-emergent insects, among different quadrants of the M. bimucronata canopy. To determine the occurring species, the emergence of bruchids and parasitoids was observed in the laboratory, resulting altogether, only in individuals of A. schrankiae and Horismenus sp. (Hymenoptera: Eulophidae) species, respectively. Mean number of fruits produced in the median region of inflorescence was significantly higher than in the inferior and superior regions, and the frequencies (observed and expected) of predated and non-predated seeds differed among the different regions of inflorescence. Females of A. schrankiae laid their eggs on fruits, and larvae, after emergence, perforated the exocarp to reach the seeds. Most fruits presented one to three eggs and only one bruchid larva was observed in each seed. The highest value of the rate number of eggs/fruit and the highest percentage of predated seeds were recorded in April. Dry weight of fruits (total) and seeds (non-predated), proportions of predated seeds, seed abortions, and non-emergent seed predators, were evenly distributed in the canopy.