Whitefly, aphids and thrips attack on cabbage

O objetivo deste trabalho foi investigar as relações entre predadores, parasitóides, composição química foliar, níveis de nitrogênio e de potássio foliar, pluviosidade, umidade relativa, insolação e temperatura média na intensidade de ataque de mosca-branca, pulgão e tripes em repolho. As populações de mosca-branca, pulgões e tripes tenderam a aumentar no final do cultivo ou apresentaram pico 40 dias depois do transplantio. As populações de mosca-branca e tripes tenderam a aumentar sob temperaturas mais elevadas. As populações de Cheiracanthium inclusum e Adialytus spp. dependiam das populações de mosca-branca e pulgões, respectivamente. Não se detectou efeito significativo entre os níveis foliares de K e nonacosano e a população de pulgões; entretanto, aumento nos níveis de N foliar resultou em menor população da praga. Não se detectou relação significativa entre os níveis foliares de N, K e nonacosano e as populações de mosca-branca e de tripes. Altos níveis foliares de nonacosano foram observados 40 dias depois do transplantio, e a umidade relativa correlacionou-se negativamente com os níveis de nonacosano. Inimigos naturais, especialmente o parasitóide Adialytus spp. e as aranhas, podem ser agentes de controle biológico eficazes de mosca-branca e pulgões em repolho. A temperatura pode aumentar as populações de mosca-branca e tripes.The objective of this work was to investigate the relationships between predators and parasitoids, leaf chemical composition, levels of leaf nitrogen and potassium, total rainfall, relative humidity, daylight and median temperature on the intensity of whitefly, aphid, and thrips attack on cabbage. Whitefly, aphids and thrips population tended to proliferate in the final stage of plant or reached a peak population about 40 days after plantation. The whitefly and thrips tended to increase with an increase in the median temperature. A dependence of Cheiracanthium inclusum and Adialytus spp. populations on whitefly and aphids populations, respectively, was observed. No significant effect was detected between K and nonacosane leaf content and aphid population. However, an increase in leaf N content was followed by a decrease of this insect population. No significant relation was observed between leaf N, K and nonacosane and whitefly and thrips populations. Highest nonacosane levels were observed in plants 40 days after transplant, and relative humidity correlated negatively with nonacosane. Natural enemies, especially the parasitoid Adialytus spp. and the spiders can be useful controlling agents of the whitefly and aphids in cabbage. Median temperature can increase whitefly and thrips populations

Qualidade da semente e senescência de genótipos de soja sob dois níveis de infestação de percevejos (Pentatomidae)

The objective of this research was to evaluate the genotypes CR-1 and CR-3, from the genetic improvement program of soybean flavor of the Federal University of Viçosa, in Viçosa, MG, Brazil, under two levels of Heteroptera infestation. The genotypes tested were CR-1, CR-3, Cristalina, Davis (susceptible genotype) and IAC-100 (resistant genotype). The genotypes CR-1, CR-3, Davis and Cristalina under low level of infestation (2.8 Heteroptera/beating) produced similar percentage of normal seeds (57%) but inferior to the genotype IAC-100 (77%). Under high level of infestation (6.42 Heteroptera/beating), the genotypes CR-1, CR-3 and Cristalina produced similar percentage of normal seeds but inferior to the genotypes Davis (43%) and IAC-100 (59%). All genotypes showed low level of leaves retention (less than 6%) when cultivated under low level of infestation by Heteroptera but under high level of infestation of these bugs, the genotypes CR-1 and IAC-100 showed smallest level of leaf retention (less than 5%) followed by Davis and CR-3 (6-20%) and Cristalina (21-40%). The genotypes CR-1, IAC-100 and Davis showed no green stem under low infestation, contrary to what was registered for CR-3 (3.6% green stem) and Cristalina (11% green stem). IAC-100, CR-1, and Davis showed the smallest percentages of plants with green stem (6.4, 10.3 and 18.3%, respectively) compared to CR-3 (64.8%) and Cristalina (77.3%).Este trabalho objetivou estudar a resistência de duas linhagens de soja, do programa de melhoramento do sabor da Universidade Federal de Viçosa, MG, cultivadas sob dois níveis de infestação de percevejos, em comparação com três cultivares de soja. Os genótipos estudados foram: CR-1, CR-3, Cristalina (linhagem paterna), Davis (padrão de suscetibilidade) e IAC-100 (padrão de resistência). CR-1, CR-3, Davis e Cristalina, sob baixa infestação, produziram porcentagens de sementes normais semelhantes entre si (57%), e inferiores às de IAC-100 (77%). Sob alta infestação, CR-1, CR-3 e Cristalina produziram percentagens de sementes normais semelhantes entre si (22%) e infe-riores às de Davis (43%) e IAC-100 (59%). Todos os genótipos apresentaram baixo grau de retenção foliar (menos que 6%) quando cultivados sob baixa infestação, mas sob alta infestação, a CR-1 e IAC-100 apresentaram menores porcentagens de retenção foliar (menos que 5%), seguida por Davis e CR-3 (6-20%) e Cristalina (21-40%). CR-1, IAC-100 e Davis não apresentaram plantas com caule verde sob baixa infestação, ao contrário do que foi registrado com CR-3 (3,6%) e Cristalina (11%). IAC-100, CR-1 e Davis apresentaram menores porcentagens de plantas com caule verde (6,4, 10,3 e 18,3%, respectivamente) que CR-3 (64,8%) e Cristalina (77,3%)

Abundância de Bemisia tabaci, Brevicoryne brassicae e Thrips tabaci em Brassica oleracea var. acephala

Kale Brassica oleracea var. acephala is attacked by whitefly Bemisia tabaci, aphid Brevicoryne brassicae and Thrips tabaci. One of the main reasons for extensive insecticide application is the lack of information about factors that control insect population. The objectives of this study were to investigate the relationships between predators and parasitoids, organic compound leaves, levels of leaf nitrogen and potassium, total rainfall, relative humidity, sunlight and median temperature on the abundance of whitefly, aphid, and thrips in kale genotype "Talo Roxo". The beating tray method, direct counting and magnifying lens were used to estimate the number of these pests, predators and parasitoids. Median temperature, sunlight and relative humidity correlated to the amount of leaf nonacosane, which in turn was associated with aphids population increase. A tendency in the reduction of aphids and thrips populations with increase in total rainfall was observed. The whitefly can be a harmful pest in kale producing regions of higher temperature and smaller rainfall. In regions which present moderate temperature, where there is a high incidence of aphids, genotype with low leaf wax content should be chosen. Natural enemies, especially the parasitoid Adialytus spp., can control agents of the aphids population in kale.A couve, Brassica oleracea var. acephala, é atacada por mosca-branca Bemisia tabaci, pulgão Brevicoryne brassicae e tripes Thrips tabaci. Uma das principais razões para o uso intensivo de inseticidas é a falta de informação sobre os fatores que controlam a população de insetos. O objetivo deste estudo foi investigar as relações entre predadores e parasitóides, compostos orgânicos foliares, níveis foliares de nitrogênio e de potássio, pluviosidade total, umidade relativa, insolação e temperatura média na abundância da mosca-branca, pulgões e tripes em couve genótipo Talo Roxo. Foi usado o método da batida em bandeja, contagem direta e lupas de aumento para estimar o número dessas pragas, de predadores e de parasitóides. A temperatura média, insolação e umidade relativa correlacionaram com nonacosano foliar que, por sua vez, esteve associado com o aumento populacional de pulgões. Foi observada uma tendência na redução de pulgões e de tripes com o aumento da pluviosidade total. A mosca-branca pode ser uma praga prejudicial em regiões produtoras de couve de maior temperatura e de menor pluviosidade. Em regiões onde se tem maior incidência de pulgões (regiões de temperatura moderada) deve-se escolher um genótipo com baixo conteúdo foliar de cera. Inimigos naturais, especialmente o parasitóide Adialytus spp., podem ser agentes de controle da população de pulgões em couve

Whitefly population dynamics in okra plantations

O controle da mosca-branca Bemisia tabaci (Gennadius) biótipo B (Hemiptera: Aleyrodidae) em quiabeiro (Abelmoschus esculentus L.) consiste principalmente no uso de inseticidas, em virtude da falta de informação sobre outros fatores de mortalidade. O objetivo deste trabalho foi compreender a dinâmica populacional, espacial e temporal da mosca-branca em dois cultivos sucessivos de quiabeiro "Santa Cruz". Avaliaram-se a composição química foliar, os níveis foliares de nitrogênio e de potássio, a densidade de tricomas, a altura de dossel, a idade de planta, predadores, parasitóides, pluviosidade total, temperatura média e suas relações com a mosca-branca em quiabeiro. Estimou-se, mensalmente, o número de adultos e de ninfas (inspeção visual) e de ovos (lentes de aumento) de mosca-branca ocorridos nas folhas (uma folha/planta) localizadas nas partes basal, mediana e apical de 30 plantas/plantação. Os fatores que mais contribuíram com a redução da população mosca-branca foram a senescência de plantas e inimigos naturais, principalmente Encarsia sp., Chrysoperla spp. e Coccinellidae. O segundo cultivo de quiabo, a 50 m do primeiro, foi altamente atacado pela mosca-branca, provavelmente pela migração dos insetos do primeiro para o segundo cultivo. Não foi detectado efeito significativo do dossel de plantas sobre ovos e adultos. Foi encontrado maior número de ninfas na parte mediana do que na parte basal das plantas.The control of whitefly Bemisia tabaci (Gennadius) biotype B (Hemiptera: Aleyrodidae) on okra (Abelmoschus esculentus L.) consists primarily in the use of insecticides, due to the lack of information on other mortality factors. The objective of this study was to evaluate the spatial and temporal population dynamics of the whitefly B. tabaci biotype B on two successive A. esculentus var. "Santa Cruz" plantations. Leaf chemical composition, leaf nitrogen and potassium contents, trichome density, canopy height, plant age, predators, parasitoids, total rainfall and median temperature were evaluated and their relationships with whitefly on okra were determined. Monthly number estimates of whitefly adults, nymphs (visual inspection) and eggs (magnifying lens) occurred on bottom, middle and apical parts of 30 plants/plantation (one leaf/plant). Plants senescence and natural enemies, mainly Encarsia sp., Chrysoperla spp. and Coccinellidae, were some of the factors that most contributed to whitefly reduction. The second okra plantation, 50 m apart from the first, was strongly attacked by whitefly, probably because of the insect migration from the first to the second plantation. No significant effects of the plant canopy on whitefly eggs and adults distribution were found. A higher number of whitefly nymphs was found on the medium part than on the bottom part

Attack of Atarsocoris brachiariae Becker, a new pest of pasturelands in Mato Grosso, Brazil

Estudou-se o efeito da textura do solo, relevo, espécie forrageira, idade e sistema de formação da pastagem, sobre o ataque de Atarsocoris brachiariae. Não foram observadas diferenças significativas entre as espécies de forrageiras ou tipo de relevo quanto ao ataque da praga. As maiores densidades foram observadas em solos de textura arenosa, pastagens com mais de quatro anos, sistema de formação convencional e na faixa de 20-30 cm de profundidade. O ataque foi em reboleiras, e a maior densidade ocorreu na região de transição entre a área de pastagem morta e a área em que esta apresentava desenvolvimento normal.The effect of soil texture, landscape, grass species, age and system of pasture formation on attack intensity of Atarsocoris brachiariae Becker was studied. No differences were found among grass species or landscape on attack intensity of this bug. Higher densities of A. brachiariae were observed in sandy soils, in pastures over four years old, in those with traditional formation and between 20-30 cm underground. Attack of A. brachiariae occurred in patches specially in the transition areas between dead grass and normal growing grass

Diversidad zoológica asociada a un silvopastoreo leucaena-guinea con diferentes edades de establecimiento

The aim of this work was to evaluate the associated zoological diversity of a silvopastural system leucaena-guinea grass, by characterizing the composition and structures of the birds, insects and the macrofauna of the soil, in four establishment times of the silvopastural systems (3, 4, 5 and 6 years of exploitation). For the species recorded in each zoological group, the following ecological indices were determined: number of individuals, richness, diversity and abundance of species, in each establishment times of the system. A significant increase, in all the zoological groups, was observed for the richness of species and for the index of biological diversity of Shannon, as the system developed. An increase in the abundance of bioregulator insects was observed, and for the birds, the sampling time showed no interaction with the different sowing years. The macrofauna of the soil increased during the management of the system, and a dominance of annelids (Polyferetrina elongata and Oligochaeta elegans) was noted during the 6th and 7th year of exploitation. The silvopastural system leucaena-guinea grass increases the biomass production and other biological components, and contributes to create a sustainable system which is compatible with the environment.The aim of this work was to evaluate the associated zoological diversity of a silvopastural system leucaena-guinea grass, by characterizing the composition and structures of the birds, insects and the macrofauna of the soil, in four establishment times of the silvopastural systems (3, 4, 5 and 6 years of exploitation). For the species recorded in each zoological group, the following ecological indices were determined: number of individuals, richness, diversity and abundance of species, in each establishment times of the system. A significant increase, in all the zoological groups, was observed for the richness of species and for the index of biological diversity of Shannon, as the system developed. An increase in the abundance of bioregulator insects was observed, and for the birds, the sampling time showed no interaction with the different sowing years. The macrofauna of the soil increased during the management of the system, and a dominance of annelids (Polyferetrina elongata and Oligochaeta elegans) was noted during the 6th and 7th year of exploitation. The silvopastural system leucaena-guinea grass increases the biomass production and other biological components, and contributes to create a sustainable system which is compatible with the environment.El objetivo de este trabajo fue evaluar la diversidad zoológica asociada a un silvopastoreo con leucaena-guinea, por medio de la caracterización de la composición y estructura de las aves, insectos y la macrofauna del suelo, en cuatro edades de establecimiento (3, 4, 5 y 6 años de explotación). Con las especies registradas en cada uno de estos grupos zoológicos, se calcularon los índices ecológicos: número de individuos, riqueza, diversidad y abundancia de especies, en diferentes edades del sistema. En todos los grupos, se apreció el aumento significativo en la riqueza de especies y en el índice de diversidad biológica de Shannon, en la medida que se desarrolló el sistema. Se observó incremento en la abundancia de insectos biorreguladores y, en relación con las aves, el horario de muestreo no mostró interacción con los distintos años de siembra. La macrofauna se incrementó, observándose dominancia de anélidos al 6o y 7o año de explotación, caracterizado por Polyferetrina elongata y Oligochaeta elegans. El desarrollo del silvopastoreo leucaena-guinea logra sistemas productivos pecuarios que aumentan la producción de biomasa y de otros componentes biológicos y contribuir para crear un sistema sostenible y compatible con el ambiente

Factors affecting the attack rate of Bemisia tabaci on cucumber

O objetivo deste trabalho foi determinar os efeitos de pluviosidade, temperatura, predadores, parasitóides, idade de planta, composição química foliar, níveis de nitrogênio e potássio foliares, assim como de densidade de tricomas, na intensidade de ataque de Bemisia tabaci biótipo B em Cucumis sativus. Observaram-se maiores números de adultos e de ninfas de mosca-branca por folha com o aumento de idade de plantas. Adultos por folha e ovos cm-2 foram encontrados com maior freqüência na parte apical do que na parte mediana e basal do dossel das plantas. Entretanto, observou-se maior número de ninfas desse inseto no terço mediano do que nos terços apical e basal. Nitrogênio foliar afetou negativamente ninfas de mosca-branca. Pentacosano e octacosano afetaram positivamente adultos e o primeiro composto afetou também as ninfas dessa praga.The objective of this work was to determine the effects of rainfall, temperature, predators, parasitoids, plant age, leaf chemical composition, levels of leaf nitrogen and potassium, besides density of leaf trichomes, on attack intensity of Bemisia tabaci biotype B on the Cucumis sativus. An increase in the number of whitefly adults and nymphs per leaf was observed with plant aging. A higher number of whitefly adults per leaf and eggs cm-2 was verified in the apical part than in the middle and bottom part of the plants canopy. However, the higher number of whitefly nymphs was observed in the mid-part than in the apical and bottom part of the plant canopy. The incidence of whitefly nymphs was negatively affected with foliar nitrogen. Pentacosane and octacosane positively affected whitefly adults and the first compound also affected the nymphs of this pest species

Efeito de tricomas, aleloquímicos e nutrientes na resistência de Lycopersicon hirsutum à traça-do-tomateiro

The objective of this work was to study the effect of trichomes, alellochemicals and minerals in the leaves of different canopy heights on the resistance of Lycopersicon hirsutum to tomato leaf miner, Tuta absoluta (Lepidoptera: Gelechiidae). Effects of 2-tridecanone (2-TD), 2-undecanone (2-UD), N, P, K, Ca and Mg levels, density and types of trichomes and leaf area on apical, medium and basal parts of plant dossel of L. hirsutum and L. esculentum on the oviposition and mines number of T. absoluta was studied. Production of 2-TD increased from the bottom to the top of the canopy. The apical part of plants of L. hirsutum showed more antibiotic effect on the caterpillar. T. absoluta oviposited more on leaves of the apical and medium portion of the plants than in the basal parts of L. esculentum.Estudos foram conduzidos com o objetivo de verificar o efeito de tricomas, aleloquímicos e nutrientes nas folhas de partes do dossel das plantas na resistência de Lycopersicon hirsutum à traça-do-tomateiro, Tuta absoluta (Lepidoptera: Gelechiidae). Foram quantificados os teores de 2-tridecanona (2-TD), 2-undecanona (2-UD), N, P, K, Ca e Mg, densidade e tipos de tricomas e tamanho das folhas nos terços apical, mediano e basal do dossel de plantas de L. hirsutum e de L. esculentum e estudaramse os efeitos destes fatores sobre características biológicas de T. absoluta. Observou-se elevação no teor de 2-TD da base para o ápice do dossel. Não se detectou diferença significativa quanto ao número de ovos de T. absoluta ao longo do dossel de L. hirsutum, constatando-se em L. esculentum maior oviposição nos terços apical e mediano do que no basal. As folhas do terço apical de L. hirsutum apresentaram maior efeito deletério sobre as larvas de traça

Natural Occurrence and Ecology of Trichogramma pretiosum (Hymenoptera: Trichogrammatidae) in Cotton Plantations with Insecticides Spraying in Minas Gerais State, Brazil

Pest damage is one of the greatest problems in cotton production in the world. The objective of this study was to assess the natural occurrence, parasitism rate, number of adults ofTrichogramma emerged and coexistence with predators species in cotton plantations with insecticide spraying in Brazil. Parasitoids were collected in two areas of two-hectares each with the Dp 4049 and Delta Opal cotton varieties, using 12.0 x 2.5 cm pieces of white cards with an average of 3.000 Anagasta kuehniella (Zeller) (Lepidoptera: Pyralidae) eggs each. The predation percentage of A. kuehniella eggs in the field and parasitism occurrence was estimated based on the cards with eggs of this prey brought from the field. All parasitoids obtained were identified as Trichogramma pretiosum (Riley) (Hymenoptera: Trichogrammatidae). The predators collected were identified as belonging to the families Chrysopidae (Neuroptera), Coccinelidae (Coleoptera) and Sirphidae (Diptera). The average number of eggs parasitized per cardboard, during the cycle of this culture was 16.34 ± 5.1 in the area with Dp-4049 and 23.38 ± 4.3 in that with Delta opal. The predation average during the cycle of this culture was 42.58 ± 3.8 e 35.58 ± 2.9% in these areas, respectively. It is necessary to preserve and to increase the performance of T. pretiosum in cotton plantations

Quality control of Trichogramma atopovirilia and Trichogramma pretiosum (Hym.: Trichogrammatidae) adults reared under laboratory conditions

The objective of this work was to assess the flight capacity, parasitism and emergence of Trichogramma atopoviriliaand two strains of T. pretiosum (Hymenoptera: Trichogrammatidae) (L1 and L2). The flight capacity of these species was assessed in test units consisting of a plastic PVC cylinder with a rigid transparent plastic circle on the upper part and an extruded polystyrene disk closing its bottom. A tube was placed in each test unit containing a card with 300 Anagasta kuehniella (Lepidoptera: Pyralidae) eggs parasitised by Trichogramma. These cards were assessed to determine the parasitism rate and adult emergence of these natural enemies. T. atopovirilia and T. pretiosum L1 presented adequate flight capacity and parasitism, in addition to high percentages of adults emerged