Alexander Machado Auad

Economic impact of exotic insect pests in Brazilian agriculture

Agriculture represents one of the major strengths of the economic sector in Brazil. The need to avoid economic losses because of insect pest populations is one of the greatest challenges faced by this sector. Insect pests have caused annual losses of US

Seleção de genótipos de capim-elefante quanto à resistência à cigarrinha-das-pastagens

12.0 billion to the Brazilian economy, of which approximately US

The impact of temperature on biological aspects and life table of Rhopalosiphum padi (Hemiptera: Aphididae) fed with signal grass.

1.6 billion are because of exotic pest species. Furthermore, exotic insect species often show greater potential to cause harm than native species. In Brazil, since the late nineteenth century, 24 species of insect pests have been introduced into the country, and they have caused significant economic losses. Many of these species, including Bemisia tabaci, Hypothenemus hampei, Ceratitis capitata, Oryzophagus oryzae and Anthonomus grandis, are major crop pests, and they were accidentally introduced during trading of agricultural products. In this review, we present an overview of Brazilian agriculture, a brief history of the introduction of insect pests in the country and the Brazilian legislation on agricultural defence, and we estimate the economic losses caused to the Brazilian economy by the main insect pest species that have been introduced into Brazil over the last 112 years.

Estimativas de repetibilidade para caracteres forrageiros em Panicum maximum

The objective of this work was to evaluate genotypes of elephant grass (Pennisetum purpureum Schum.) regarding resistance to the spittlebug Mahanarva spectabilis. For antibiosis evaluation, each plant was infested with six eggs near hatching, thirty days after planting, in a completely randomized design with 30 genotypes and ten repetitions. Forty-five days after the nymphs hatched, the insect survival rate was evaluated on the different genotypes. For nonpreference mechanism evaluation, the size and number of the nymphs per pot were assessed every 15 days, in plants kept at greenhouse, where adults of M. spectabilis were periodically released, in a completely randomized design, with three repetitions per genotype in two sampling periods. Cameroon de Piracicaba, Pioneiro, Cuba 169, Santa Rita, Mineiro Ipeaco, Mercker Comum de Pinda and CNPGL 96-27-3 genotypes were selected for resistance, by antibiosis mechanism. In the study of the nonpreference mechanism, the number and average size of the nymphs varied significantly as a function of the elephant grass genotype. Roxo de Botucatu and Pioneiro genotypes are, respectively, susceptible and resistant check candidates by the antibiosis mechanism, and Cameroon and Cameroon Piracicaba genotypes are promising by the nonpreference mechanism.

Comportamento agronômico de populações de azevém anual (Lolium multiflorum L.) para cultivo invernal na região sudeste

ABSTRACT The impact of temperature was evaluated on Rhopalosiphum padi (L.) (Hemiptera: Aphididae). Nymphs, 12-h-old, were placed individually in cylindrical plastic dishes (2.5 × 2.5 cm), with a layer of 1% agar in which leaf disks of signal grass had been placed. The nymphs were reared at 12, 16, 20, 24, 28, and 32°C ± 1°C, RH of 70 ± 10% and 12-h photophase. We evaluated number of instars, duration of each instar and the nymphal period, survival of instars, duration of the reproductive period, daily and total production of nymphs, and longevity of the nymphal and adult phases. To construct the life expectancy table and fecundity, daily observations were made of 70 nymphs at each temperature, from birth to death. Development of R. padi was faster with increased temperature, but they did not complete the last nymphal instar at 32°C. The same pattern occurred for the pre-reproductive, reproductive, and post-reproductive periods. The highest fecundity rates were between 16°C and 24°C. The highest fertility (4 nymphs/female/day) was recorded at 12°C and 20°C. The highest net reproduction rates were at 24°C and 28°C, and the time interval between each generation (T) and the population doubling time (DT) diminished as temperature increased. The finite rate of increase (&lgr; = 1.9 nymphs/female/day) and the intrinsic rate of increase (rm = 0.64) were greatest at 24°C and 28°C, respectively. There was a negative impact on the biology and life table of R. padi at 32°C, but the range of 12°C to 28°C, despite some fluctuations, was favorable for survival and reproduction. Translation by the authors.

Eficiência de Chrysoperla externa (Hagen, 1861)(Neuroptera: Chrysopidae) no controle de Myzus persicae (Sulzer, 1776) (Hemiptera: Aphididae) em pimentão (Capsicum annum L.)

Objetiva-se com este trabalho estimar a repetibilidade para caracteres forrageiros de Panicum, e determinar o numero de cortes de avaliacao necessarios para a selecao de genotipos de Panicum, com confiabilidade. Utilizaram-se os dados de um ensaio conduzido no periodo de 21/11/2002 a 08/04/2005, no Campo Experimental da Embrapa Gado de Leite, localizado em Valenca-RJ, onde foram realizados 15 cortes de avaliacao. No ensaio, foram avaliados 23 genotipos de Panicum maximum, em parcelas experimentais, dispostas no delineamento de blocos casualizados, com tres repeticoes. Foram estimados os coeficientes de repetibilidade para as caracteristicas producao de materia verde de forragem (PMV); producao de materia seca de forragem (PMS) e de folhas (PMSF); porcentagem de folhas na PMS (%FOL) e altura da planta (AP), utilizando os metodos da analise de variância, componentes principais e analise estrutural. Para todas as caracteristicas avaliadas os efeitos de genotipos, cortes e interacao genotipos x cortes foram significativos (P<0,01). Quando se considerou o coeficiente de determinacao de 85%, o numero de avaliacoes (cortes) necessarios para a determinacao do valor real dos genotipos foram de 10, 9, 7, 11 e 3, respectivamente, para PMV, PMS, PMSF, %FOL e AP. O metodo dos componentes principais e o da analiseestrutural (baseado na matriz de correlacoes) foram concordantes para todas as caracteristicas avaliadas. A realizacao de 10 cortes de avaliacao permite discriminar o valor real dos genotipos de Panicum, com confiabilidade superior a 85%, para a maioria das caracteristicas avaliadas.

Desenvolvimento e reprodução de Sipha flava (Forbes) (Hemiptera: Aphididae) em diferentes temperaturas

Na Regiao Sudeste o periodo do inverno e caracterizado pela escassez e perda de qualidade das pastagens, sendo o azevem anual uma das forrageiras invernais mais recomendadas para suplementacao da dieta dos rebanhos leiteiros nesta epoca do ano. Com este trabalho, buscou-se avaliar o comportamento de populacoes de azevem resultantes de coleta de germoplasma. Foram avaliadas 30 populacoes, sendo 22 resultantes de coletas recentes realizadas na Regiao Sul e oito pertencentes a colecao da Embrapa. Foi utilizado o delineamento experimental de blocos ao acaso com tres repeticoes, sendo realizados sete cortes. Foram avaliados: altura da planta, porcentagem e producao de materia seca, rebrota, numero de dias ate o florescimento e producao de sementes. Observou-se variacao entre as populacoes para todas as caracteristicas avaliadas. A estimativa da producao total de materia seca variou de 3654 kg/ha (populacao LE 284) a 8544 kg/ha (CNPGL 164). Os resultados demonstraram elevado potencial de producao de forragem entre as populacoes de azevem coletadas, sendo que algumas delas podem ser recomendadas para cultivo invernal na Regiao Sudeste.

Application methods of entomopathogenic nematodes for control of Mahanarva spectabilis (Hemiptera: Cercopidae)

Avaliou-se a eficiencia de larvas de primeiro instar de Chrysoperla externa no controle Myzus persicae em pimentao, em experimentos realizados em câmara e sala climatizadas a 25 ± 1oC, UR de 70 ± 10% e fotofase de 12 horas. Larvas de C. externa recem-eclodidas foram liberadas em discos foliares, contendo 5; 10 ou 20 ninfas do afideo, acondicionados em placas de Petri. Em um segundo experimento, larvas do predador foram liberadas nas proporcoes 1:5, 1:10 e 1:20, em plantas inoculadas com 60; 100 e 140 ninfas do pulgao. O potencial predatorio de C. externa nos discos foliares foi influenciado pela densidade inicial do pulgao. A eficiencia do predador nas densidades de 5; 10 e 20 pulgoes foi de 100%; 96,7% e 79,3%, respectivamente. A eficiencia das larvas em eliminar as populacoes do pulgao nas plantas de pimentao variou em funcao do tempo. Na proporcao 1:5, a eliminacao das ninfas ocorreu entre um e dois dias apos a liberacao do predador, enquanto nas proporcoes 1:10 e 1:20 o periodo de quatro dias nao foi suficiente para que os pulgoes fossem eliminados. As larvas de C. externa quando liberadas nas tres proporcoes promoveram reducoes na populacao de M. persicae, se comparada a testemunha. No entanto, nas proporcoes 1:5 e 1:10 o predador se mostrou mais eficiente.

Tabela de esperança de vida e de fertilidade de Sipha flava (Forbes) (Hemiptera, Aphididae) alimentado com capim-elefante em diferentes temperaturas

The aphid Sipha flava (Forbes) is a pest on elephant grass, but little is known about its biology. The objective of this work was to evaluate the temperature effects on the development, survival and reproduction of S. flava fed on Pennisetum purpureum. Twelve-hour-old nymphs were individualized on sections of elephant grass blades and maintained at 12, 16, 20, 24, 28 and 32 degrees C+/-1 degrees C, UR 70+/-10% and 12 h photophase. A total of 150 nymphs were used per treatment divided in 30 replicates, using a totally random design. The lower threshold temperatures (LTT) for first, second, third and fourth instars were 0.83, 1.05, 3.01 and 4.98 degrees C, respectively, indicating a change in thermal requirements as the development progress. The LTT for the whole nymphal stage was 2.08 degrees C, pointing to the tolerance of this species to low temperatures. A significant reduction in survival was observed at high temperatures (28 and 32 degrees C). Although the reproductive periods were longer and insects lived longer at 12 degrees C as compared with those at higher temperatures, the total fecundity was substantially reduced. The overall life cycle duration was almost twice as long at 12 degrees C than at 24 degrees C. The greatest daily production of nymphs and greatest number of nymphs produced overall occurred at 24 degrees C. The temperatures of 20 degrees C and 24 degrees C were more suitable to S. flava development and reproduction.

Flutuação populacional de cigarrinhas-das-pastagens em braquiária e capim-elefante

Abstract The pathogenicity of entomopathogenic nematodes (EPNs) against nymphs of the pasture spittlebug Mahanarva spectabilis (Distant, 1909) (Hemiptera: Cercopidae) was studied under four application methods. Nymphs of the fourth or fifth instar were placed on the roots of elephant grass plants and submitted to four EPN isolates (Steinernema carpocapsae, S. feltiae, S. riobravis and Heterorhabditis amazonensis RSC1), at two concentrations (2000 and 4000 infective juveniles/mL), with four application methods (pipetting, spraying on the nymphs after froth formation, spraying before froth formation and placement of infected host cadaver method). There was no significant difference in the nymph mortality in function of the concentration and/or the isolate used. However, the efficacy was influenced by the application method, with the most efficient being sprayed on nymphs after froth formation and infected host cadavers. Steinernema riobravis applied by spraying on nymphs with froth, at a concentration of 2000 EPNs/mL, and H. amazonensis RSC1 applied by infected host cadavers caused 71% of the nymphs to die. The use of infected host cadavers and spraying in an aqueous solution on nymphs after froth formation were found to be the most efficient methods to control Mahanarva spectabilis.