Marcos Gino Fernandes

Distribuição espacial de plantas infestadas por Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) na cultura do milho

The importance of the fall armyworm, Spodoptera frugiperda (J.E. Smith), is not only due to the damage it can cause, but also to its difficult control. It is essential to know the pest population parameters, such as its standard scattering in the crop, because depending on the space arrangement of the insects in the area, different sampling methods are required. For the present work, three experimental fields were installed in different areas: the first one had 66 plots with seven plants each; the second one had 55 plots with four plants each; and the third field had 55 plots with six plants each. The presence or absence of the pest in the plant was evaluated in the samples. According to the data observed, either to the scattering index or to the theoretical scattering models, S. frugiperda dispersion is scattered at random and strongly depends on the infestation level.

Harmonia axyridis (Coleoptera: Coccinellidae) Exhibits No Preference between Bt and Non-Bt Maize Fed Spodoptera frugiperda (Lepidoptera: Noctuidae)

A recent shift in managing insect resistance to genetically engineered (GE) maize consists of mixing non-GE seed with GE seed known as “refuge in a bag”, which increases the likelihood of predators encountering both prey fed Bt and prey fed non-Bt maize. We therefore conducted laboratory choice-test feeding studies to determine if a predator, Harmonia axyridis, shows any preference between prey fed Bt and non-Bt maize leaves. The prey species was Spodoptera frugiperda, which were fed Bt maize (MON-810), expressing the single Cry1Ab protein, or non-Bt maize. The predators were third instar larvae and female adults of H. axyridis. Individual predators were offered Bt and non-Bt fed prey larvae that had fed for 24, 48 or 72 h. Ten and 15 larvae of each prey type were offered to third instar and adult predators, respectively. Observations of arenas were conducted at 1, 2, 3, 6, 15 and 24 h after the start of the experiment to determine the number and type of prey eaten by each individual predator. Prey larvae that fed on non-Bt leaves were significantly larger than larvae fed Bt leaves. Both predator stages had eaten nearly all the prey by the end of the experiment. However, in all combinations of predator stage and prey age, the number of each prey type consumed did not differ significantly. ELISA measurements confirmed the presence of Cry1Ab in leaf tissue (23–33 µg/g dry weight) and S. frugiperda (2.1–2.2 µg/g), while mean concentrations in H. axyridis were very low (0.01–0.2 µg/g). These results confirm the predatory status of H. axyridis on S. frugiperda and that both H. axyridis adults and larvae show no preference between prey types. The lack of preference between Bt-fed and non-Bt-fed prey should act in favor of insect resistance management strategies using mixtures of GE and non-GE maize seed.

Sequential sampling of Aphis gossypii Glover (Hemiptera: Aphididae) and Frankliniella schultzei Trybom (Thysanoptera: Thripidae) on cotton crop

The goal of this research was to use the sequential probability ratio test to establish a sequential sampling plan for Aphis gossypii Glover and Frankliniella schultzei Trybom infesting cotton. Field work was conducted at the agricultural experimental station of the Universidade Federal da Grande Dourados during the 2003/2004 and 2004/2005 agricultural years. Aphid colonies and individual thrips in the sampling area were counted and their numbers were recorded. The spatial distribution pattern of A. gossypii and F. schultzei in the cotton culture was aggregated. Sequential sampling plans were developed for aphids and thrips with type I and type II errors set at 0.1, common Kc = 0.6081 (aphids) and = 0. 9449 (thrips), and safety and management levels of 20% (aphids) and 40% (thrips) of infested plants. The sampling plans resulted in two decision boundaries for each species, as follows: the upper boundary, indicating when management (population control) is recommended: S1 = 4.6546 + 0.2849n (aphids), and S1 = 3.6514 + 0.1435n (thrips); and the lower boundary, indicating when population control is not necessary: S0 = -4.6546 + 0.2849n (aphids) and S0 = - 3.6514 + 0.1435n (thrips). The highest probability of error when making a decision was 3% for aphids and 2% for thrips, respectively. The maximum number of samples required to reach a decision was 63 for aphids and 95 for thrips.

First confirmed record of harmonia axyridis (pallas, 1773) (coleoptera: Coccinellidae) in the state of Mato Grosso do Sul, Brazil

Harmonia axyridis is a predator of aphids and other soft-bodied insects. This coccinellid, native to Asia, has invaded North America, Europe, South America and Africa. We report the first detection of H. axyridis in the Brazilian state of Mato Grosso do Sul, and review its current known geographic distribution in Brazil. Based on experiences from other parts of the world already invaded by H. axyridis , recommendations are provided to maximize the potential benefits offered by this species, while minimizing the potential adverse impacts that it can cause.

Riqueza e composição de espécies de insetos visitantes florais de algodoeiro Bt e não-Bt

This study aimed to verify the difference between flower-visiting insect communities in genetically modified cotton (Bt) and conventional cotton (non-Bt). The study was conducted in a commercial cotton field in the municipality of Maracaju, Mato Grosso do Sul, Brazil. The collections of flower visitors were performed every 3 days in the morning during the reproductive period of cotton and employed 2 treatments: Bt cotton and non-Bt cotton. By the end of flowering, 1,310 specimens were collected, 56.56% on Bt cotton flowers and 43.44% on non-Bt cotton flowers. Even though the abundance of collected insects on Bt cotton was higher, species richness in non-Bt was higher than Bt, with a diversity of 73 species on Bt cotton and 84 species on non-Bt. Species richness of flower visitors varied between sampling times for both treatments and between the days of flowering, therefore, the species richness was lower at the beginning and the end of flowering in both cotton cultivars. But the species richness did not vary between cultivars of cotton. Species composition of insects was different during the periods of flower visitation, between cotton cultivars as well as between the interaction of these two factors. There was also a variation between the days of flowering but not between days and cotton cultivars. Based on this study, it was concluded that there are differences between the species of insects that visit flowers of Bt cotton and non-Bt cotton.

Efeitos da adubação nitrogenada em algodoeiro sobre a biologia de Aphis gossypii Glover (Hemiptera: Aphididae)

The cotton aphid, Aphis gossypii Glove, is one of the pests of cotton crop and its relation with the host seem to depend on the amount of nitrogen available to the plant. The biology of A. gossypii using different cotton nitrogen fertility regimes was studied under greenhouse conditions, in Dourados, MS. A completely randomized design with nine replications in a factorial scheme (2x4x2)+1 was used. Two nitrogen sources (sulphate of ammonium and urea), four doses of nitrogen (50, 100, 150 and 200 kg ha-1), two different times of nitrogen application and one additional treatment without nitrogen were taken as factors. The nymphal phases, the pre-reproductive, reproductive and pos-reproductive periods, longevity, the life cycle and fecundity of the cotton aphid were evaluated. The doses of nitrogen influenced the cotton aphid biology in both sources and times of application, favoring its development and fecundity.

Distribuição espacial de Aedes albopictus na região sul do Estado de Mato Grosso do Sul

OBJETIVO: Estudar a distribuicao espacial da populacao de Aedes albopictus, visando fornecer subsidios para construcao de planos de amostragem e decisao sobre o controle deste vetor em levantamentos em campo. METODOS: O estudo foi realizado em area urbana proxima de resquicios de vegetacao primaria, no distrito Picadinha, distante 20 km do municipio de Dourados, MS. Dez amostragens foram realizadas entre 28/1/2003 e 9/4/2003, utilizando-se armadilhas do tipo ovitrampas e monitoradas semanalmente, distribuidas em uma area amostral fixa com 10 pontos de coleta por amostragem, espacadas em 300 m. Foram calculados os indices de agregacao e ajuste as seguintes distribuicoes teoricas de frequencia: binomial negativa, binomial positiva e de Poisson. RESULTADOS: A variância amostral foi superior a media nas amostragens, resultando nos indices de razao variância-media sempre acima da unidade (32,066, 29,410, 14,444, 58,840, 56,042, 111,262, 70,140, 50,701, 93,221 e 8,481). O indice de Morisita apresentou valores significativamente acima da unidade em todas as amostragens (6,275, 3,947, 1,484, 3,725, 3,014, 5,450, 3,214, 3,886, 3,954 e 5,810). O parâmetro K resultou em valores entre 0 e 8 (0,174, 0,309, 1,867, 0,332, 0,449, 0,203, 0,408, 0,314, 0,306 e 0,200). Os testes do qui-quadrado de ajuste as distribuicoes binominal negativa, binomial positiva e de Poisson nao foram significativos. CONCLUSOES: A populacao de Aedes albopictus da localidade estudada apresentou distribuicao espacial padrao agregada. Isso implica que ao encontrar alguns individuos do vetor em um determinado local, e provavel que outros sejam encontrados nas areas circunvizinhas, preconizando a aplicacao de inseticidas sem a necessidade de amostrar outros pontos dessa localidade.

DESFOLHA ARTIFICIAL SIMULANDO DANOS DE PRAGAS NA CULTURA DO MILHETO

O objetivo desta pesquisa foi avaliar os componentes de producao de plantas do milheto submetidos a niveis crescentes de desfolha de 0; 25; 50; 75 e 100%, realizadas nos estadios fenologicos (ED1, ED4 e ED7). O experimento foi composto por 15 tratamentos, dispostos em blocos ao acaso, com quatro repeticoes. As variaveis avaliadas foram diâmetro do colmo, massa seca da parte aerea e produtividade de graos de milheto. A maior reducao do diâmetro do colmo ocorre com 100% de desfolha em ED4. Desfolhas acima de 25% afetam a produtividade de graos, no estadio ED1, na cultura a campo. No estadio ED1, desfolha de 50%, reduz a massa seca da parte aerea e nas desfolhas de 75 e 100% nao afeta a produtividade das plantas.

Sequential sampling of Bemisia tuberculata (Bondar, 1923) (Hemiptera: Aleyrodidae) on cassava crop

Estimate efficiently of the whitefly population (Bemisia tuberculata Bondar) in cassava, to assist in decision making of pest control is one of the advantages of sequential sampling plans. Therefore, the objective of this study was to determine a sequential sampling plan according to two methods of pest management, using biological and/or chemical control. Samples were obtained in a commercial field of 2.500,00 m2, divided into 100 plots. The visualization method was used for sampling of the upper leaves by counting the number of adults. In total 15 samples were taken weekly from January to April 2012. The spatial distribution model which best fit to the behavior of B. tuberculata adults was the negative binomial distribution. Levels adapted for biological and chemical control were five and twenty adults per plant, respectively. Sampling plans resulted in two decisions for each proposed method. Thus, for population control the upper limit was defined as S1 = 4.2056 + 2.1540n (biological) and S1 = 20.219 + 10.4306n (chemical); and the lower limit where the pest control is not recommended was defined by S0 = -4.2056 + 2.1540n (biological) and S0 = -20.219 + 10.4306n (chemical). Sequential sampling estimated the maximum number of sample units necessary for decision-making of three samples with 1.34 adults for biological control and 3.85 sample units with 7.39 adult pests for chemical control.

Biological parameters of the non-target pest Aphis gossypii Glover (Hemiptera: Aphididae) on genetically modified (GM) Bt cotton

In the present work, we aimed to evaluate: 1) the influence of the Cry1Ac protein expressed by the genetically modified cotton variety ( Bt ) NuOpal, on the biological parameters of a non-target pest, Aphis gossypii , reared under laboratory conditions; 2) the influence of plant age on aphid development. Cotton cultivars were grown following technical advice. In the laboratory, the aphids were separated into plastic containers including a cotton sheet, which was changed daily with the help of a moist cotton cloth. Observations were carried out daily, and the duration of the immature and adult stages, and offspring number, were recorded. Our results show that regardless of the differences in the duration of each instar, cultivars Bt and non-Bt and the different ages of the plant to Bt, no differences were seen in the total duration of these phases. It was only during the reproductive period that differences were observed among genotypes for 120 days. Regarding the number of offspring and longevity total, there were differences between the different ages of the Bt treatment. Keywords : Biosafety, transgenic, Gossypium hirsutum , genetically modified (GM) plant African Journal of Biotechnology Vol. 12(16), pp. 1987-1992