Efeitos não-alvo de inseticidas utilizados para controle de Bemisia tabaci (Gennadius, 1889) biótipo B (Hemiptera: Aleyrodidae) sobre a mortalidade e biologia de Spodoptera frugiperda (Smith, 1797) (Lepidoptera: Noctuidae) em soja [Glycine max (l.) Merrill]

Spodoptera frugiperda Smith (Lepidoptera: Noctuidae) is a polyphagous pest that has gained importance in soybean cultivation in recent years, due to the damage it causes to leaves and pods. The objective of this work was to evaluate the non-target effect of insecticides recommended and used to control Bemisia tabaci (Genn.) biotype B on S. frugiperda. The experimental design was entirely randomized with five treatments and fifty replications. The treatments were: 1. negative control (distilled water), 2. positive control (lufenuron), 3. buprofezin, 4. pyriproxyfen, and 5. diafenthiuron. In each replicate, one caterpillar was placed in a plastic cup, where sprayed soybean leaves with the maximum dosage of insecticides recommended for B. tabaci were placed.The treatments were evaluated daily during all stages: larval, pupal, and adult emergence and fecundity. The results obtained for larval mortality showed that diafenthiuron aimed 100% control, followed by pyriproxyfen with 28% and buprofezin with 12%. The duration of the larval period of the insects exposed to pyriproxyfen and buprofezin were longer compared to the control. While the biological parameters of pupae were found that pyriproxyfen caused lower pupal formation rate and higher pupal mortality, followed by buprofezin. In adult emergence, pyriproxyfen showed the lowest rate with 13.8% and the highest percentage of deformed adults with 60%. Thus, it was possible to conclude that the insecticides under study cause S. frugiperda mortality or effects on its biological patterns

Parasitismo natural de ovos de Alabama argillacea Hüb. e Heliothis virescens Fab. (Lep.: Noctuidae) por Trichogramma pretiosum Riley (Hym.: Trichogrammatidae) em algodoeiros no Mato Grosso do Sul

Os experimentos foram conduzidos em culturas comerciais de algodoeiros na região de Dourados no Estado de Mato Grosso do Sul, durante a safra 1996/97. Observaram-se os seguintes aspectos do parasitismo natural em ovos de Alabama argillacea Hübner e Heliothis virescens Fabricius por Trichogramma pretiosum Riley: índice de parasitismo, razão sexual e número de adultos emergidos por ovo. Realizou-se coleta semanal de ovos dos lepidópteros e sua incubação em laboratório. Aos 31 dias após a emergência das plantas (DAE), não se observou parasitismo nos ovos de A. argillacea. Porém, a partir de 58 dias (DAE), acima de 60% dos ovos estavam parasitados por T. pretiosum, atingindo em algumas avaliações quase 100%. Apesar da baixa ocorrência de ovos de H. virescens, esses também apresentaram elevado índice de parasitismo por T. pretiosum. O número de fêmeas emergidas dos ovos parasitados geralmente foi maior do que o de machos. Fêmeas representaram em torno de 60% do total de adultos emergidos na maioria das coletas efetuadas. O número de adultos emergidos por ovo de A. argillacea e H. virescens foi ao redor de dois. Na região de Dourados, portanto, o parasitismo natural em ovos de A. argillacea e H. virescens por T. pretiosum é elevado, mesmo com as freqüentes aplicações de inseticidas.The experiments were carried out on cotton in the region of Dourados, Mato Grosso do Sul State, in 1996-97. From weekly samples of eggs of Alabama argillacea Hüb. and Heliothis virescens Fab., we determined the level of parasitism, sex ratio and total number of adults of Trichogramma pretiosum Riley emerged from each host egg. The percentage of A. argillacea eggs parasitized by T. pretiosum was null at 31 days after the emergence of the plants (DAE) and increased to more than 60% from the 58th day (DAE)on; sometimes the parasitism reached almost 100%. H. virescens eggs also showed high levels of parasitism by T. pretiosum. The number of adult females emerged from parasitized eggs was always higher than the number of adult males and represented around 60% of the total adults emerged. on the average, around two adult wasps emerged from each egg of A. argillacea or H. virescens. In the region of Dourados, the parasitism by T. pretiosum was high in both A. argillacea and H. virescens eggs, despite the high levels of insecticide use

Spatial Distribution of Eggs of Alabama argillacea Hübner and Heliothis virescens Fabricius (Lepidoptera: Noctuidae) on Bt and non-BtCotton

ABSTRACT Among the options to control Alabama argillacea (Hübner, 1818) and Heliothis virescens (Fabricius, 1781) on cotton, insecticide spraying and biological control have been extensively used. The GM'Bt' cotton has been introduced as an extremely viable alternative, but it is yet not known how transgenic plants affect populations of organisms that are interrelated in an agroecosystem. For this reason, it is important to know how the spatial arrangement of pests and beneficial insect are affected, which may call for changes in the methods used for sampling these species. This study was conducted with the goal to investigate the pattern of spatial distribution of eggs of A. argillacea and H. virescens in DeltaOpalTM (non-Bt) and DP90BTMBt cotton cultivars. Data were collected during the agricultural year 2006/2007 in two areas of 5,000 m2, located in in the district of Nova América, Caarapó municipality. In each sampling area, comprising 100 plots of 50 m2, 15 evaluations were performed on two plants per plot. The sampling consisted in counting the eggs. The aggregation index (variance/mean ratio, Morisita index and exponent k of the negative binomial distribution) and chi-square fit of the observed and expected values to the theoretical frequency distribution (Poisson, Binomial and Negative Binomial Positive), showed that in both cultivars, the eggs of these species are distributed according to the aggregate distribution model, fitting the pattern of negative binomial distribution

Spatial Distribution of Euschistus heros (Hemiptera: Pentatomidae) in Cotton (Gossypium hirsutum Linnaeus)

Abstract Recently, the Neotropical brown stink bug, Euschistus heros (Pentatomidae: Hemiptera), has been detected in cotton in the Brazilian Cerrado. Several reliable surveys have been conducted on the spatial distribution of stink bugs in soybean; however, few studies have examined the behavior of this insect in cotton in Brazil. Thus, this study examined the spatial distribution of E. heros in cotton using aggregation indices based on the variance-to-mean ratio, Morisita index, exponent k, Poisson and negative binomial distributions. Inverse Distance Weighting interpolation maps were also used to represent insect density. The study was conducted in a 1.1 hectare experimental cotton field in which 64 equally-sized plots were sampled on a weekly basis. Our findings revealed that stink bugs presented an aggregate distribution in 2 sampling weeks based on aggregation indices, and this pattern was best described by a negative binomial distribution. Maps showing the density of pests can be an important tool for sampling pests in crops and control measures in early stages of infestation, when there is an edge effect on the distribution of E. heros, can be an efficient strategy in cotton