Effect of a Voltage Probe on the Phase-Coherent Conductance of a Ballistic Chaotic Cavity

The effect of an invasive voltage probe on the phase-coherent conduction through a ballistic chaotic cavity is investigated by random-matrix theory. The entire distribution P(G) of the conductance G is computed for the case that the cavity is coupled to source and drain by two point contacts with a quantized conductance of 2 e^2/h, both in the presence (beta = 1) and absence (beta = 2) of time-reversal symmetry. The loss of phase-coherence induced by the voltage probe causes a crossover from P(G) ~ G^(-1 + beta/2) to a Gaussian centered at G = e^2/h with a beta-dependent width. ***Submitted to Physical Review B.***Comment: 9 pages, REVTeX-3.0, 4 postscript figures appended as self-extracting archive, INLO-PUB-941020

Larval dispersal of Spodoptera frugiperda strains on Bt Cotton: a model for understanding resistance evolution and consequences for its management.

High dispersal of Lepidoptera larvae between non-Bt and Bt cotton plants can favour the evolution of insect resistance; however, information on host acceptance of neonates in tropical transgenic crops is scarce. Therefore, the purposes of this study were as follows: (i) to investigate the feeding behaviour of susceptible and Cry1F-resistant strains of Spodoptera frugiperda (J.E. Smith) on Bt and non-Bt cotton (Gossypium hirsutum L.) varieties and (ii) to understand the possible effects of cotton field contamination on the dispersal and infestation capacity of S. frugiperda larvae by using an individualbased model. The main results of this paper are as follows: (1) the highest post-feeding larval dispersal of the Cry1F-resistant strain occurred at an exposure time of 18?24 h; (2) via video tracking assays, we found that the least distance moved was by larvae resistant to Cry1F on non-Bt cotton; and (3) the model indicated differences in mobility capacity between Bt and non-Bt cotton. We conclude that resistant neonates exhibit sedentary behaviour. Our report represents the first findings concerning the fitness cost of larval behaviour traits of S. frugiperda associated with Cry1F resistance in Brazilian populations.Publicado online em 23 de novembro de 2017

Interspecific associations between cycloneda sanguinea and two aphid species (Aphis gossypii and Hyadaphis foeniculi) in Sole-crop and fennel-cotton intercropping systems.

Aphids cause significant damage to crop plants. Studies regarding predator-prey relationships in fennel (Foeniculum vulgare Mill.) and cotton (Gossypium hirsutum L.) crops are important for understanding essential ecological interactions in the context of intercropping and for establishing pest management programs for aphids. This study evaluated the association among Hyadaphis foeniculi (Passerini) (Hemiptera: Aphididae), Aphis gossypii Glover (Hemiptera: Aphididae) and Cycloneda sanguinea (L.) (Coleoptera: Coccinellidae) in cotton with coloured fibres, fennel and cotton intercropped with fennel. Association analysis was used to investigate whether the presence or absence of prey and predator species can indicate possible interactions between aphids and ladybugs. Significant associations among both apterous and alate H. foeniculi and C. sanguinea were observed in both the fennel and fennel-cotton intercropping systems. The similarity analysis showed that the presence of aphids and ladybugs in the same system is significantly dependent on the type of crop. A substantial amount of evidence indicates that the presence of the ladybug C. sanguinea, is associated with apterous or alate A. gossypii and H. foeniculi in fennel-cotton intercropping system. We recommend that future research vising integrated aphid management taking into account these associations for take decisions

Population dynamics of Aphis gossypii Glover and Aphis craccivora Koch (Hemiptera: Heteroptera: Aphididae) in sole and intercropping systems of cotton and cowpea.

Population dynamics of aphids have been studied in sole and intercropping systems. These studies have required the use of more precise analytical tools in order to better understand patterns in quantitative data. Mathematical models are among the most important tools to explain the dynamics of insect populations. This study investigated the population dynamics of aphids Aphis gossypii and Aphis craccivora over time, using mathematical models composed of a set of differential equations as a helpful analytical tool to understand the population dynamics of aphids in arrangements of cotton and cowpea. The treatments were sole cotton, sole cowpea, and three arrangements of cotton intercropped with cowpea (t1, t2 and t3). The plants were infested with two aphid species and were evaluated at 7, 14, 28, 35, 42, and 49 days after the infestations. Mathematical models were used to fit the population dynamics of two aphid species. There were good fits for aphid dynamics by mathematical model over time. The highest population peak of both species A. gossypii and A. craccivora was found in the sole crops, and the lowest population peak was found in crop system t2. These results are important for integrated management programs of aphids in cotton and cowpea

Fungicides performance on the control of asian soybean rust (Phakopsora pachyrhizi) in Goias State, Brazil.

The use of fungicides remains the most important tool to Asian soybean rust (ASR) control in Brazil. The reduction of the Phakopsora pachyrhizi sensibility to triazols changed the strategy to the exclusive use of fungicides to strobilurines with triazols premix formulations. Two field trials of the Brazilian network for ASR chemical control were conducted in Goiania and Senador Canedo at Goias State in order to compare the efficacy of 17 fungicides on ASR control. The treatments were composed by two triazols, one strobilurine, one carboxanilide, and 13 premix formulations of strobilurine + triazol. The fungicides were applied twice, beginning at soybean growth stage R1 in absence of ASR symptoms (preventatively), and 21 days after first spray. The soybean cultivars were BRS 8160 RR in Goiania and BRS Valiosa RR in Senador Canedo. The area under disease progress curve (AUDPC) was calculated for each treatment based on four ASR severity evaluations from R1 to R7 soybean growth stages. The lower AUDPC and higher soybean yield were observed for almost all fungicides in premix formulations of strobilurine with triazols. The carboxanilide oxycarboxin and the triazols tebuconazole and cyproconazole were not so efficient on ASR control. The lowest reductions of soybean cycle due to ASR were observed with picoxystrobin + tebuconazole, which were 12 days later in relation to the untreated plots in Goiania and 10 days later in Senador Canedo