Manejo de afídeos e nanismo-amarelo em trigo: eficácia em três safras.

Decisões para o manejo de afídeos e nanismo-amarelo em trigo são adotadas com base em níveis populacionais dos insetos. Enquanto vetores de vírus, afídeos causam danos mesmo em baixos níveis populacionais. A eficácia do controle varia em função das medidas de manejo com inseticidas utilizadas, incluindo a forma de aplicação, o momento e o número das pulverizações. Neste trabalho, avaliou-se a eficácia de estratégias de manejo com inseticidas usualmente empregadas para o controle de afídeos como pragas diretas e como vetores de barley/cereal yellow dwarf virus (B/CYDV), em uma sequência de safras de trigo. Em experimento de campo, a incidência de afídeos e de nanismo-amarelo e a produtividade do trigo foram avaliadas nas safras de 2014, 2015 e 2016, nos tratamentos TT - tratamento total (tratamento de sementes+aplicação semanal de inseticidas), para avaliar o potencial produtivo da cultura; TS ? tratamento de sementes com inseticida; PA - pulverização de inseticidas em parte aérea das plantas ao atingir o nível de ação; TS+PA; e SI - sem inseticidas (testemunha). Aplicação de inseticidas em sementes e em pulverização aérea baseada no nível de ação, para controle de afídeos entre a emergência e espigamento das plantas, proporcionou produtividades entre 10,6 e 22,9% superiores em relação ao manejo sem inseticidas. Quando a infestação de afídeos ocorre logo após a emergência, a eficácia de controle não depende do método de aplicação de inseticida (TS ou PA). Devido à dificuldade de serem previstos a época e o nível de infestação de afídeos e à facilidade operacional, o tratamento de sementes é recomendável.bitstream/item/224685/1/BolPesqDes-99-o.pd

Optimizing drip irrigation for eggplant crops in semi-arid zones using evolving thresholds

AbstractField experiments were combined with a numerical model to optimize drip irrigation management based on soil matric potential (SMP) measurements. An experimental crop of eggplant was grown in Burkina Faso from December 2014 to March 2015 and plant response to water stress was investigated by applying four different irrigation treatments. Treatments consisted in using two different irrigation depths (low or high), combined with a water provision of 150%, 100% or 66% (150/100/66) of the maximum crop evapotranspiration (T150low, T66low, T100high, T66high). Soil matric potential measurements at 5, 10 and 15cm depth were taken using a wireless sensor network and were compared with measurements of plant and root biomass and crop yields. Field data were used to calibrate a numerical model to simulate triggered drip irrigation. Different simulations were built using the software HYDRUS 2D/3D to analyze the impact of the irrigation depth and frequency, the irrigation threshold and the soil texture on plant transpiration and water losses. Numerical results highlighted the great impact of the root distribution on the soil water dynamics and the importance of the sensor location to define thresholds. A fixed optimal sensor depth of 10 cm was found to manage irrigation from the vegetative state to the end of fruit development. Thresholds were defined to minimize water losses while allowing a sufficient soil water availability for optimal crop production. A threshold at 10cm depth of −15kPa is recommended for the early growth stage and −40kPa during the fruit formation and maturation phase. Simulations showed that those thresholds resulted in optimal transpiration regardless of the soil texture so that this management system can constitute the basis of an irrigation schedule for eggplant crops and possibly other vegetable crops in semi-arid regions

The Embrace Magnetometer Network for South America: First Scientific Results

The present work is the second of a two-part paper on the Embrace Magnetometer Network. In this part, we provide some of the first scientific findings that we have already achieved with this network. We identified the diurnal and the seasonal natural variations of the H component. We provided the precise determination of sudden storm commencements and sudden impulse. We showed that the ΔH amplitudes derived from the Embrace MagNet during intense magnetic storm are in very good agreement with the Dst index. We showed that it is possible to investigate the effects on the solar quiet ionospheric current systems as a response to the X-class solar flares occurring during daytime under magnetically quiet conditions.Facultad de Ciencias Astronómicas y Geofísica

The Embrace Magnetometer Network for South America: Network Description and Its Qualification

The present work is the first of a two-part paper on the Embrace Magnetometer Network. In this part, we present the new Embrace Magnetometer Network (Embrace MagNet) in South America, which is originally planned to cover most of the eastern portion of the Southern America longitudinal sector by installing and operating fluxgate magnetometer stations. We discuss the purpose and scientific goals of the network, associated with aeronomy and space weather. We provide details on the instrumentation, location of the sensors, sensitivity matching process, gain matching process, and magnetometer installation. In addition, we present and discuss details about the data storage, near-real time display, and availability.Facultad de Ciencias Astronómicas y Geofísica

Influence of preservation methods, sample medium and sampling time on eDNA recovery in a neotropical river

Environmental DNA (eDNA) has rapidly emerged as a promising biodiversity monitoring technique, proving to be a sensitive and cost‐effective method for species detection. Despite the increasing popularity of eDNA, several questions regarding its limitations remain to be addressed. We investigated the effect of sampling medium and time, and preservation methods, on fish detection performance based on eDNA metabarcoding of neotropical freshwater samples. Water and sediment samples were collected from 11 sites along the Jequitinhonha River, Southeastern Brazil; sediment samples were stored in ethanol, while the same amounts of water per sample (3 L) were stored in a cool box with ice, as well as by adding the cationic surfactant benzalkonium chloride (BAC). Sediment and water samples yielded a similar amount of fish MOTUs (237 vs. 239 in the first sampling event, and 153 vs. 142 in the second sampling event). Water stored in ice provided better results than those preserved in BAC (239 and 142 vs. 194 and 71 MOTUs). While documenting the effectiveness of eDNA surveys as practical tools for fish biodiversity monitoring in poorly accessible areas, we showed that keeping water samples cooled results in greater eDNA recovery and taxon detection than by adding cationic surfactants (BAC) as sample preservatives. Furthermore, by comparing two sets of samples collected from the same locations at a 3‐week interval, we highlight the importance of conducting multiple sampling events when attempting to recover a realistic picture of fish assemblages in lotic systems

The Embrace Magnetometer Network for South America: First Scientific Results

The present work is the second of a two-part paper on the Embrace Magnetometer Network. In this part, we provide some of the first scientific findings that we have already achieved with this network. We identified the diurnal and the seasonal natural variations of the H component. We provided the precise determination of sudden storm commencements and sudden impulse. We showed that the ΔH amplitudes derived from the Embrace MagNet during intense magnetic storm are in very good agreement with the Dst index. We showed that it is possible to investigate the effects on the solar quiet ionospheric current systems as a response to the X-class solar flares occurring during daytime under magnetically quiet conditions.Facultad de Ciencias Astronómicas y Geofísica