Simone Martins Mendes

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

Respostas da lagarta‑do‑cartucho a milho geneticamente modificado expressando a toxina Cry 1A(b)

12.0 billion to the Brazilian economy, of which approximately US

Estádio de adaptação de Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) em hospedeiros alternativos

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.

Rapid selection and characterization of Cry1F resistance in a Brazilian strain of fall armyworm

O objetivo deste trabalho foi avaliar parâmetros biologicos da lagarta-do-cartucho do milho (Spodoptera frugiperda), alimentada com hibridos de milho Bt, que expressam a toxina Cry 1A(b), e com seus respectivos isogenicos nao Bt. Os experimentos foram realizados no laboratorio da Embrapa Milho e Sorgo, em Sete Lagoas, MG. Os parâmetros avaliados foram: sobrevivencia de larvas apos 48 horas, sobrevivencia da fase larval e pre-imaginal, biomassa de larvas aos 14 dias de idade, biomassa de pupas, periodo de desenvolvimento larval, e nao preferencia alimentar de larvas do primeiro instar. Larvas de S. frugiperda apresentam menor sobrevivencia nas primeiras 48 horas de alimentacao e durante toda a fase larval, na maioria dos hibridos de milho Bt, em comparacao ao milho nao Bt. A biomassa de larvas e pupas foi sempre menor no milho Bt, e o periodo larval e o pre-imaginal, maior. Houve interacao entre a toxina Cry 1A(b) e a base genetica dos hibridos transgenicos, quanto a sobrevivencia e a biomassa larval. Larvas recem-eclodidas de S. frugiperda apresentam preferencia pela alimentacao em milho nao Bt.

Life-History Traits of Spodoptera frugiperda Populations Exposed to Low-Dose Bt Maize

A principal praga-alvo na cultura do milho e a lagarta-do-cartucho, Spodoptera frugiperda (J.E. Smith, 1797) (Lepidoptera: Noctuidae), que, pela sua ampla distribuicao temporal e geografica constitui-se em uma das especies mais nocivas nas regioes tropicais das Americas. O objetivo foi avaliar o estadio de adaptacao de S. frugiperda em 17 especies hospedeiras, cultivadas ou selvagens, mais comuns no agroecossistema brasileiro. As plantas foram cultivadas em cinco epocas, entre 2006 e 2008, utilizando o milho como padrao. Larvas de S. frugiperda recem-eclodidas foram individualizadas e confinadas em copo plastico (50 mL), onde foram alimentadas com secoes de folha nova de cada hospedeiro. O alimento foi substituido a cada dois dias por folhas frescas. Quatro variaveis biologicas foram avaliadas e utilizadas para se calcular um Indice de Adaptacao (IA). Os resultados indicaram que a sobrevivencia inicial de S. frugiperda variou de 100%, no milho, a 46%, no arroz. O periodo larval variou de 12,6 dias, no milho, a 27,1 dias, na grama batatais. A biomassa de pupa variou de 173,1 mg, no carrapicho, a 294,2 mg, no milho. O indice de adaptacao, calculado com base nas variaveis biologicas de S. frugiperda, nos hospedeiros avaliados, variou de 17,43, no milho cultivado na epoca I, a 1,46, na cana-de-acucar na epoca III. Para corrigir o efeito de epoca sobre o indice de adaptacao de S. frugiperda nos hospedeiros, foi calculado o Indice Relativo de Adaptacao (IRA), com base no indice de adaptacao no milho (100%). Assim, com base no indice relativo de adaptacao, estimado em condicoes de laboratorio, os hospedeiros alternativos ao milho, para S. frugiperda, podem ser assim ordenados, do maior para o menor indice: sorgo granifero, sorgo selvagem, milheto, capim-tanzânia, amendoim, capim-marandu, capim-braquiaria, caruru-de-porco, trigo, soja, algodao, feijao, arroz, capim-carrapicho, grama batatais e cana-de-acucar.

Diversidade molecular entre populações de Spodoptera frugiperda no Brasil avaliada por marcadores AFLP

Transgenic maize (Zea mays L., Poaceae) event TC1507, producing the Cry1F protein of Bacillus thuringiensis Berliner, has been used for management of the fall armyworm, Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae), in Brazil since 2009. A strain of S. frugiperda, obtained from field collections of larvae in TC1507 maize in Minas Gerais state in 2010, was selected in the laboratory for resistance to Cry1F using leaves of TC1507 maize in two selection regimes. Continuous exposure of larvae to Cry1F was more effective than exposure for 6, 8, and 10 days in the selection of resistant S. frugiperda individuals. With only four generations of laboratory selection, a strain with high levels of resistance to Cry1F was obtained, as indicated by the survival of insects reared on leaves of TC1507 maize plants and by the more than 300‐fold resistance level measured in bioassays with the purified Cry1F protein. Importantly, reciprocal crosses between control and the Cry1F‐selected strains revealed that the resistance is autosomal and incompletely recessive, and the response obtained in the backcross of the F1 generation with the resistant strain was consistent with simple monogenic inheritance. Additionally, there were no apparent fitness costs associated with resistance either for survival or larval growth on non‐Bt maize leaves. Our findings provide experimental evidence for rapid evolution of Cry1F resistance in S. frugiperda in the laboratory and further reinforce the potential of this species to evolve field resistance to the TC1507 maize as previously reported. The resistant strain isolated in this study provides an opportunity to estimate the resistance allele frequency in the field and to determine the biochemical and molecular basis of the resistance, which should provide further information to assist in the resistance management of S. frugiperda on transgenic maize producing B. thuringiensis proteins.

Seleção de clones de braquiária para resistência à lagarta‑do‑cartucho

Exposure to Bacillus thuringiensis (Bt) toxins in low- and moderate-dose transgenic crops may induce sublethal effects and increase the rate of Bt resistance evolution, potentially compromising control efficacy against target pests. We tested this hypothesis using the fall armyworm Spodoptera frugiperda, a major polyphagous lepidopteran pest relatively tolerant to Bt notorious for evolving field-relevant resistance to single-gene Bt maize. Late-instar larvae were collected from Bt Cry1Ab and non-Bt maize fields in five locations in Brazil, and their offspring was compared for survival, development, and population growth in rearing environment without and with Cry1Ab throughout larval development. Larval survival on Cry1Ab maize leaves varied from 20 to 80% among the populations. Larvae reared on Cry1Ab maize had seven-day delay in development time in relation to control larvae, and such delay was shorter in offspring of armyworms from Cry1Ab maize. Population growth rates were 50–70% lower for insects continuously exposed to Cry1Ab maize relative to controls, showing the population-level effect of Cry1Ab, which varied among the populations and prior exposure to Cry1Ab maize in the field. In three out of five populations, armyworms derived from Bt maize reared on Cry1Ab maize showed higher larval weight, faster larval development and better reproductive performance than the armyworms derived from non-Bt maize, and one of these populations showed better performance on both Cry1Ab and control diets, indicating no fitness cost of the resistance trait. Altogether, these results indicate that offspring of armyworms that developed on field-grown, single-gene Bt Cry1Ab maize had reduced performance on Cry1Ab maize foliage in two populations studied, but in other three populations, these offspring had better overall performance on the Bt maize foliage than that of the armyworms from non-Bt maize fields, possibly because of Cry1Ab resistance alleles in these populations. Implications of these findings for resistance management of S. frugiperda in Bt crops are discussed.

Crop losses and the economic impact of insect pests on Brazilian agriculture

O objetivo deste trabalho foi avaliar a diversidade molecular, por meio de marcadores AFLP, de seis populacoes de Spodoptera frugiperda coletadas na cultura do milho, em diferentes regioes geograficas do Brasil. O DNA foi extraido de lagartas de quarto instar, e as reacoes de AFLP foram realizadas com sete combinacoes de oligonucleotideos iniciadores. A partir das seis populacoes de S. frugiperda estudadas, foi identificado um grupo principal formado por tres populacoes geneticamente mais relacionadas. As populacoes de S. frugiperda analisadas mostram alta variabilidade genetica, com maximo de 58% de similaridade.

Occurrence of fumonisins and zearalenone in maize stored in family farm in Minas Gerais, Brazil

The objective of this work was to evaluate and select signal grass (Urochloa ruziziensis) clones resistant to fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), for use in a crop-livestock-forest integration system. One hundred and forty-seven clones of U. ruziziensis were evaluated in a completely randomized design with three replicates. An artificial diet, adequate for insect development, was used as a control and susceptibility standard. Leaves of different U. ruziziensis clones were collected and offered as food to the insects, kept individually in rearing units. Larval survival, duration, and biomass of larvae and pupa were evaluated. Significant differences were observed between clones for all evaluated traits, showing the marked effect of U. ruziziensis clones on the development of S. frugiperda. Twenty clones were identified in which there was no development of larvae and 55 clones in which there was an average larval survival of 33%. For the other clones, which were better hosts, insect development was affected by the longer larval stage and by the reduction in pupa biomass. The obtained results show the potential of using Urochloa ruziziensis clones for the reduction of Spodoptera frugiperda populations in a crop-livestock-forest integration system.