The multiple roles of trichomes in two Croton species.

Trichomes are common in plants from dry environments, and despite their recognized role in protection and defense, little is known about their role as absorptive structures and in other aspects of leaf ecophysiology. We combine anatomical and ecophysiological data to evaluate how trichomes affect leaf gas exchange and water balance during drought. We studied two congeneric species with pubescent leaves which co-occur in Brazilian Caatinga: Croton blanchetianus (dense trichomes) and Croton adenocalyx (sparse trichomes). We found a novel foliar water uptake (FWU) pathway in C. blanchetianus composed of stellate trichomes and underlying epidermal cells and sclereids that interconnect the trichomes from both leaf surfaces. The water absorbed by these trichomes is redistributed laterally by pectin protuberances on mesophyll cell walls. This mechanism enables C. blanchetianus leaves to absorb water more efficiently than C. adenocalyx. Consequently, the exposure of C. blanchetianus to dew during drought improved its leaf gas exchange and water status more than C. adenocalyx. C. blanchetianus trichomes also increase their leaf capacity to reflect light and maintain lower temperatures during drought. Our results emphasize the multiple roles that trichomes might have on plant functioning and the importance of FWU for the ecophysiology of Caatinga plants during drought.

Speeding up Smartphone-Based Dew Computing: In Vivo Experiments Setup Via an Evolutionary Algorithm.

Dew computing aims to minimize the dependency on remote clouds by exploiting nearby nodes for solving non-trivial computational tasks, e.g., AI inferences. Nowadays, smartphones are good candidates for computing nodes; hence, smartphone clusters have been proposed to accomplish this task and load balancing is frequently a subject of research. Using the same real-i.e., in vivo-testbeds to evaluate different load balancing strategies based on energy utilization is challenging and time consuming. In principle, test repetition requires a platform to control battery charging periods between repetitions. Our Motrol hard-soft device has such a capability; however, it lacks a mechanism to assure and reduce the time in which all smartphone batteries reach the level required by the next test. We propose an evolutionary algorithm to execute smartphone battery (dis)charging plans to minimize test preparation time. Charging plans proposed by the algorithm include charging at different speeds, which is achieved by charging at maximum speed while exercising energy hungry components (the CPU and screen). To evaluate the algorithm, we use various charging/discharging battery traces of real smartphones and we compare the time-taken for our method to collectively prepare a set of smartphones versus that of individually (dis)charging all smartphones at maximum speed.

Improvement of reference crop evapotranspiration estimates using limited data for the Brazilian Cerrado

Evapotranspiration (ET) is a key component of the hydrological cycle. Therefore, adequately estimating it is crucial to improving water resource planning and management.One of the most affordable methods of estimating ET is first to estimate reference crop evapotranspiration (ETo) and later associate it to crop and soil coefficients. The FAO Kc-ETo approach can be used only when ETo is computed with the FAO Penman-Monteith equation. However, low data availability may restict the equations used to estimate ETo. In this study, we assess and calibrate common methods used to estimate ETo under such conditions of limited data availability. Based on the annual calibration, the Makkink (NSE = 0.85) outperformed the Priestley-Taylor (NSE = 0.73), Hargreaves-Samani (NSE = 0.56), and Penman-Monteith temperature approach (NSE = 0.58). The seasonal calibration of parameters showed no significant improvement to the methods assessed (ΔNSE ≤ 0.01), except for the Priestley-Taylor (ΔNSE = 0.06). The performance of temperature-based equations was particularly limited due to the performance of the equation adopted to estimate global solar radiation. Thus, improving the representation of global solar radiation for limited data availability can also play a key role in improving ETo prediction.(AU)

Motrol: A hardware-software device for batch benchmarking and profiling of in-lab mobile device clusters.

Motrol is a simple device that satisfies functional requirements necessary for the automatic execution of battery-driven tests and profiling of connected mobile devices. It is specifically a hardware/software platform that allows Dew Computing researchers and developers to automate performance tests on Android-based smartphones. The hardware is based on a NodeMCU Esp8266 microcontroller that runs a firmware for managing the outputs. This software allows enabling/disabling the relays that connect the sockets that power the chargers of up to 4 mobile devices minimizing the need for human intervention. The firmware runs a web server that serves Rest requests from a Rest client with the commands to drive the digital outputs. These digital outputs activate or deactivate the relays to allow current to pass or not to the sockets. Such capability is essential to automate the study of battery behavior on battery-driven devices such as smartphones. Motrol is easy to assemble, knowledge in electronics or programming languages is not necessary, it is constructed with open hardware, and it is cheap, being its total cost ∼USD 30.

The Brazilian Cerrado is becoming hotter and drier.

The Brazilian Cerrado is a global biodiversity hotspot with notoriously high rates of native vegetation suppression and wildfires over the past three decades. As a result, climate change can already be detected at both local and regional scales. In this study, we used three different approaches based on independent datasets to investigate possible changes in the daytime and nighttime temperature and air humidity between the peak of the dry season and the beginning of the rainy season in the Brazilian Cerrado. Additionally, we evaluated the tendency of dew point depression, considering it as a proxy to assess impacts on biodiversity. Monthly increases of 2.2-4.0℃ in the maximum temperatures and 2.4-2.8℃ in the minimum temperatures between 1961 and 2019 were recorded, supported by all analyzed datasets which included direct observations, remote sensing, and modeling data. The warming raised the vapor pressure deficit, and although we recorded an upward trend in absolute humidity, relative humidity has reduced by ~15%. If these tendencies are maintained, gradual air warming will make nightly cooling insufficient to reach the dew point in the early hours of the night. Therefore, it will progressively reduce both the amount and duration of nocturnal dewfall, which is the main source of water for numerous plants and animal species of the Brazilian Cerrado during the dry season. Through several examples, we hypothesize that these climate changes can have a high impact on biodiversity and potentially cause ecosystems to collapse. We emphasize that the effects of temperature and humidity on Cerrado ecosystems cannot be neglected and should be further explored from a land use perspective.

Foliar water uptake in arid ecosystems: seasonal variability and ecophysiological consequences.

Foliar water uptake (FWU) has been reported for different species across several ecosystems types. However, little attention has been given to arid ecosystems, where FWU during dew formation or small rain events could ameliorate water deficits. FWU and their effects on leaf water potential (ΨLeaf) were evaluated in grasses and shrubs exploring different soil water sources in a Patagonian steppe. Also, seasonal variability in FWU and the role of cell wall elasticity in determining the effects on ΨLeaf were assessed. Eleven small rain events (< 8 mm) and 45 days with dew formation were recorded during the study period. All species exhibited FWU after experimental wetting. There was a large variability in FWU across species, from 0.04 mmol m-2 s-1 in species with deep roots to 0.75 mmol m-2 s-1 in species with shallow roots. Species-specific mean FWU rates were positively correlated with mean transpiration rates. The increase in ΨLeaf after leaf wetting varied between 0.65 MPa and 1.67 MPa across species and seasons. The effects of FWU on ΨLeaf were inversely correlated with cell wall elasticity. FWU integrated over both seasons varied between 28 mol m-2 in species with deep roots to 361 mol m-2 in species with shallow roots. Taking into account the percentage of coverage of each species, accumulated FWU represented 1.6% of the total annual transpiration of grasses and shrubs in this ecosystem. Despite this low FWU integrated over time compared to transpiration, wetting leaves surfaces can help to avoid larger water deficit during the dry season.

How do leaf wetting events affect gas exchange and leaf lifespan of plants from seasonally dry tropical vegetation?

Foliar uptake of dew is likely an important mechanism of water acquisition for plants from tropical dry environments. However, there is still limited experimental evidence describing the anatomical pathways involved in this process and the effects of this water subsidy on the maintenance of gas exchange and leaf lifespan of species from seasonally dry tropical vegetation such as the Brazilian caatinga. We performed scanning electron, bright-field and confocal microscopic analyses and used apoplastic tracers to examine the foliar water uptake (FWU) routes in four woody species with different foliar phenology and widely distributed in the caatinga. Leaves of plants subjected to water stress were exposed to dew simulation to evaluate the effects of the FWU on leaf water potentials, gas exchange and leaf lifespan. All species absorbed water through their leaf cuticles and/or peltate trichomes but FWU capacity differed among species. Leaf wetting by dew increased leaf lifespan duration up to 36 days compared to plants in the drought treatment. A positive effect on leaf gas exchange and new leaf production was only observed in the anisohydric and evergreen species. We showed that leaf wetting by dew is relevant for the physiology and leaf lifespan of plants from seasonally dry tropical vegetation, especially for evergreen species.

Foliar water uptake in Amazonian trees: Evidence and consequences.

The absorption of atmospheric water directly into leaves enables plants to alleviate the water stress caused by low soil moisture, hydraulic resistance in the xylem and the effect of gravity on the water column, while enabling plants to scavenge small inputs of water from leaf-wetting events. By increasing the availability of water, and supplying it from the top of the canopy (in a direction facilitated by gravity), foliar uptake (FU) may be a significant process in determining how forests interact with climate, and could alter our interpretation of current metrics for hydraulic stress and sensitivity. FU has not been reported for lowland tropical rainforests; we test whether FU occurs in six common Amazonian tree genera in lowland Amazônia, and make a first estimation of its contribution to canopy-atmosphere water exchange. We demonstrate that FU occurs in all six genera and that dew-derived water may therefore be used to "pay" for some morning transpiration in the dry season. Using meteorological and canopy wetness data, coupled with empirically derived estimates of leaf conductance to FU (kfu ), we estimate that the contribution by FU to annual transpiration at this site has a median value of 8.2% (103 mm/year) and an interquartile range of 3.4%-15.3%, with the biggest sources of uncertainty being kfu and the proportion of time the canopy is wet. Our results indicate that FU is likely to be a common strategy and may have significant implications for the Amazon carbon budget. The process of foliar water uptake may also have a profound impact on the drought tolerance of individual Amazonian trees and tree species, and on the cycling of water and carbon, regionally and globally.

Influence of meteorological variables on dengue incidence in the municipality of Arapiraca, Alagoas, Brazil

Abstract INTRODUCTION: Meteorological influences along with the lack of basic sanitation has contributed to disease outbreaks, resulting in large socio-economic losses, especially in terms of dengue. This study aimed to evaluate the meteorological influences on the monthly incidence of dengue in Arapiraca-AL, Brazil during 2008-2015. METHODS: We used generalized linear models constructed via logistic regression to assess the association between the monthly incidence of dengue (MID) of and 8 meteorological variables [rainfall (R), air temperature (AT), dew point temperature (DPT), relative humidity (RH), pressure surface, wind speed (WS), wind direction (WD), and gust], based on data obtained from DATASUS and meteorological station databases, respectively. The dengue-1 model included R, AT, DPT, and RH and the dengue-2 model included AT, DPT, RH, WS, and WD. A MID >100 (classified as moderate incidence) indicated an abnormal month. RESULTS: Based on the dengue-1 model, variables with the highest odds ratio included R-lag1, DPT-lag1, and AT-lag1 with a 10.1, 18.3, and 26.7 times greater probability of a moderate MID, respectively. Based on the dengue-2 model, variables with the highest odds ratio were AT-lag1 and RH-lag0 indicating an 8.9 and 18.1 times greater probability of a moderate MID, respectively. CONCLUSIONS: AT, DPT, R, RH and WS influenced the occurrence of a moderate MID.

Effect of the interaction between fungicide application time and rainfall simulation interval on Asian Soybean Rust control effectiveness / Efeito da interação entre horários de aplicação do fungicida e intervalos de simulação de chuva na eficácia de controle da Ferrugem Asiática da Soja

Environmental factors affect the performance of fungicides in soybean (Glycine max (L.) Merr.). They also influence the residual activity of the products applied to the leaves. The objective of this study was to assess the control effectiveness of the interaction between fungicide application and rainfall simulation on Asian Soybean Rust (ASR). Two experiments were conducted, one in the greenhouse, in a completely randomized design, and the other in the field, in a randomized block design. Both the experiments had the same factorial arrangement of 6x5, with four replications. Factor A: Five fungicide applications time at 0400 h, 0900 h, 1400 h, 1800 h, 2300 h and, a control with no application; Factor B: four intervals of time between the application of fungicide and rainfall simulation at 0, 30, 60 and 120 min for the experiment in the greenhouse and at 2, 30, 60, 120 min for the experiment in the field. A control was included for both the experiments with no rainfall. The number of days to the appearance of the first pustules was determined, along with severity of ASR, relative chlorophyll index and productivity. It was found that the ASR control effectiveness of fungicide applications in soybean plants in sunlight was less efficient with rainfall simulation. The rainfall simulation had greater negative effect on disease control effectiveness in applications conducted at night under dew conditions. The application conducted at 0900 h showed the greatest disease control effectiveness in both greenhouse and in the field conditions. The 1400 h application showed decreased fungicide control residual and ASR control effectiveness, possibly due to a combination of the low relative humidity and high temperature. Rainfall simulation carried out at 120 min after application still had the ability to affect the ASR control effectiveness.

Os fatores ambientais afetam o comportamento dos fungicidas em soja (Glycine max (L.) Merr.). Eles também influenciam a atividade residual de produtos aplicados na folha. O objetivo do estudo foi avaliar a eficácia de controle da interação entre a aplicação do fungicida e simulação de chuva na Ferrugem Asiática da Soja (FAS). Foram conduzidos dois experimentos, um em casa de vegetação em delineamento inteiramente casualizado e outro a campo em delineamento de blocos ao acaso. Ambos os experimentos tiveram o mesmo arranjo fatorial 6x5, com quatro repetições. O fator A: cinco horários de aplicação de fungicida às 04h00, 09h00, 14h00, 18h00, 23h00 e uma testemunha sem aplicação; Fator B: quatro intervalos de tempo entre a aplicação do fungicida e a simulação de chuva ao 0, 30, 60 e 120 min para o experimento em casa de vegetação e aos 2, 30, 60, 120 min para o experimento à campo. Um controle sem chuva foi incluído para ambos os experimentos. Os parâmetros avaliados foram o número de dias para o aparecimento das primeiras pústulas, severidade de FAS, índice relativo de clorofila e produtividade. Verifica-se que a eficácia de controle de FAS de aplicações de fungicidas em plantas de soja sob a luz solar foi menos afetada pela simulação de chuva. A simulação de chuva tem maior efeito negativo na eficácia de controle da doença em aplicações realizadas durante a noite sob condições de orvalho. A aplicação realizada às 09h00 apresentou a maior eficácia de controle da doença em ambas às condições de casa de vegetação e a campo. O horário de aplicação das 14h00 reduziu o residual de controle do fungicida e a eficácia de controle de FAS, possivelmente devido à combinação da baixa umidade relativa do ar e alta temperatura. Contudo, a simulação de chuva realizada aos 120 min após a aplicação ainda afetou a eficácia do controle FAS.

Effect of the interaction between fungicide application time and rainfall simulation interval on Asian Soybean Rust control effectiveness / Efeito da interação entre horários de aplicação do fungicida e intervalos de simulação de chuva na eficácia de controle da Ferrugem Asiática da Soja

Environmental factors affect the performance of fungicides in soybean (Glycine max (L.) Merr.). They also influence the residual activity of the products applied to the leaves. The objective of this study was to assess the control effectiveness of the interaction between fungicide application and rainfall simulation on Asian Soybean Rust (ASR). Two experiments were conducted, one in the greenhouse, in a completely randomized design, and the other in the field, in a randomized block design. Both the experiments had the same factorial arrangement of 6x5, with four replications. Factor A: Five fungicide applications time at 0400 h, 0900 h, 1400 h, 1800 h, 2300 h and, a control with no application; Factor B: four intervals of time between the application of fungicide and rainfall simulation at 0, 30, 60 and 120 min for the experiment in the greenhouse and at 2, 30, 60, 120 min for the experiment in the field. A control was included for both the experiments with no rainfall. The number of days to the appearance of the first pustules was determined, along with severity of ASR, relative chlorophyll index and productivity. It was found that the ASR control effectiveness of fungicide applications in soybean plants in sunlight was less efficient with rainfall simulation. The rainfall simulation had greater negative effect on disease control effectiveness in applications conducted at night under dew conditions. The application conducted at 0900 h showed the greatest disease control effectiveness in both greenhouse and in the field conditions. The 1400 h application showed decreased fungicide control residual and ASR control effectiveness, possibly due to a combination of the low relative humidity and high temperature. Rainfall simulation carried out at 120 min after application still had the ability to affect the ASR control effectiveness.(AU)

Os fatores ambientais afetam o comportamento dos fungicidas em soja (Glycine max (L.) Merr.). Eles também influenciam a atividade residual de produtos aplicados na folha. O objetivo do estudo foi avaliar a eficácia de controle da interação entre a aplicação do fungicida e simulação de chuva na Ferrugem Asiática da Soja (FAS). Foram conduzidos dois experimentos, um em casa de vegetação em delineamento inteiramente casualizado e outro a campo em delineamento de blocos ao acaso. Ambos os experimentos tiveram o mesmo arranjo fatorial 6x5, com quatro repetições. O fator A: cinco horários de aplicação de fungicida às 04h00, 09h00, 14h00, 18h00, 23h00 e uma testemunha sem aplicação; Fator B: quatro intervalos de tempo entre a aplicação do fungicida e a simulação de chuva ao 0, 30, 60 e 120 min para o experimento em casa de vegetação e aos 2, 30, 60, 120 min para o experimento à campo. Um controle sem chuva foi incluído para ambos os experimentos. Os parâmetros avaliados foram o número de dias para o aparecimento das primeiras pústulas, severidade de FAS, índice relativo de clorofila e produtividade. Verifica-se que a eficácia de controle de FAS de aplicações de fungicidas em plantas de soja sob a luz solar foi menos afetada pela simulação de chuva. A simulação de chuva tem maior efeito negativo na eficácia de controle da doença em aplicações realizadas durante a noite sob condições de orvalho. A aplicação realizada às 09h00 apresentou a maior eficácia de controle da doença em ambas às condições de casa de vegetação e a campo. O horário de aplicação das 14h00 reduziu o residual de controle do fungicida e a eficácia de controle de FAS, possivelmente devido à combinação da baixa umidade relativa do ar e alta temperatura. Contudo, a simulação de chuva realizada aos 120 min após a aplicação ainda afetou a eficácia do controle FAS.(AU)

Spatial variability of leaf wetness duration in cotton, coffee and banana crop canopies

Despite the importance of leaf wetness duration for plant disease epidemiology, there has been little attention paid to research on how its variability relates to different cropping situations. The objective of this study was to evaluate the spatial variability of leaf wetness duration (LWD) in three crops, comparing these measurements with turfgrass LWD, obtained in a standard weather station. LWD was measured by electronic sensors in three crops with different canopy structures and leaf area: cotton, coffee and banana. For the cotton crop, cylindrical sensors were deployed at the lower third and on the top of the canopy, facing southwest. For the coffee crop, flat plate sensors were installed in the lower third of the canopy facing northeast and southwest; in the middle third facing northeast and southwest; and inside and on the top of the canopy. For the banana canopy, cylindrical sensors were used to measure LWD in the lower third of the canopy and in the upper third of the plant. Turfgrass LWD was simultaneously measured in a nearby standard weather station. The LWD showed different patterns of variation in the three crop canopies. For coffee plants, the longest LWD was found in the lower portions of the canopy; for the banana crop, the upper third of the canopy showed the longest LWD; whereas for the cotton crop no difference was observed between the top and lower third of the canopy. Turfgrass LWD presented a good relationship with LWD measured on the top or in the upper third of the crops. Thus, the estimate of crop LWD can be perfomed based on turfgrass LWD, this being a useful tool for plant disease management purposes for crops in which the longer LWD occurs at the upper canopy portion.

Apesar da importância da duração do período de molhamento para a epidemiologia de doenças de plantas, pouca atenção tem sido dada à sua variabilidade em diferentes posições da cultura. O objetivo deste estudo foi avaliar a variabilidade espacial da duração do período de molhamento (DPM) em três culturas, comparando-se as medidas obtidas com a DPM medida sobre gramado em um posto meteorológico padrão. A DPM foi medida por sensores eletrônicos em três culturas com diferentes estruturas de dosséis e áreas foliares: algodão, café e banana. Na cultura do algodão, os sensores cilídricos foram instalados no terço médio e no topo do dossel voltados para o sudoeste. Na cultura do café, sensores de placa foram instalados no terço inferior do dossel voltados para nordeste e sudoeste; no terço médio também voltados para nordeste e sudoeste; no interior e no topo do dossel. Na cultura da banana, sensores cilíndricos foram instalados nos terços inferior e superior da planta. A DPM sobre gramado foi simultaneamente medida em um posto meteorológico próximo às culturas. A DPM exibiu diferentes padrões de variação nas três culturas. Para o cafeeiro, a DPM mais longa foi observada nas partes mais baixas da planta; para a bananeira, o terço superior foi o que apresentou a maior DPM; enquanto que para a cultura do algodão não houve diferença entre o topo e o interior do dossel. A DPM medida sobre gramado apresentou boa correlação com a DPM medida no topo ou no terço superior das culturas. Dessa forma, pode-se estimar a DPM nas culturas a partir da DPM do gramado, sendo esta uma ferramenta muito útil para o manejo de doenças de plantas em culturas onde a DPM mais longa ocorre nas porções superiores do dossel.

Estimating leaf wetness duration over turfgrass, and in a 'Niagara Rosada' vineyard, in a subtropical environment

Leaf wetness duration (LWD) is a key parameter in agrometeorology because it is related to plant disease occurrence. As LWD is seldomly measured in a standard weather station it must be estimated to run warning systems for schedule chemical disease control. The objective of the present study was to estimate LWD over turfgrass considering different models with data from a standard weather station, and to evaluate the correlation between estimated LWD over turfgrass and LWD measured in a 'Niagara Rosada' vineyard, cultivated in a hedgerow training system, in Jundiaí, São Paulo State, Brazil. The wetness sensors inside the vineyard were located at the top of the plants, deployed at an inclination angle of 45º and oriented southwest, with three replications. The methods used to estimate LWD were: number of hours with relative humidity above 90% (NHRH > 90%), dew point depression (DPD), classification and regression tree (CART) and Penman-Monteith (PM). The CART model had the best performance to estimate LWD over turfgrass, with a good precision (R² = 0.82) and a high accuracy (d = 0.94), resulting in a good confidence index (c = 0.85). The results from this model also presented a good correlation with measured LWD inside the vineyard, with a good precision (R² = 0.87) and a high accuracy (d = 0.96), resulting in a high confidence index (c = 0.93), showing that LWD in a 'Niagara Rosada' vineyard can be estimated with data from a standard weather station.

A duração do período de molhamento (DPM) é uma variável agrometeorológica chave para a ocorrência de doenças de plantas. Como a DPM é raramente medida nas estações meteorológicas, ela deve ser estimada quando se pretende empregar sistemas de alerta de controle químico. Desse modo, o objetivo do presente estudo foi avaliar a estimativa da DPM sobre gramado por diferentes modelos a partir de dados meteorológicos obtidos em uma estação meteorológica padrão e verificar as relações entre a DPM estimada para o gramado e a medida em um vinhedo de 'Niagara Rosada', conduzido em espaldeira, em Jundiaí, SP, Brasil. Os sensores de molhamento no vinhedo foram instalados no topo das plantas com um ângulo de inclinação de 45º e com a face superior do sensor voltada para sudoeste, com três repetições. Os quatro modelos de estimativa da DPM foram: número de horas com umidade relativa do ar acima de 90% (NHUR > 90%), depressão do ponto de orvalho (DPO), árvore de classificação e regressão (CART) e o de Penman-Monteith (PM). O modelo CART estimou melhor a DPM no gramado, apresentando uma boa precisão (R² = 0,82) e uma ótima exatidão (d = 0,94), resultando num bom índice de confiabilidade (c = 0,85). Esta estimativa também apresentou uma boa correlação com a DPM medida no interior do vinhedo, com uma precisão razoável (R² = 0,87) e uma ótima exatidão (d = 0,96), resultando num ótimo índice de confiabilidade (c = 0,93), o que permite concluir que é possível estimar a DPM no vinhedo de 'Niagara Rosada' por meio de dados medidos ou estimados na estação meteorológica padrão.

Performance of cylindrical leaf wetness duration sensors in a tropical climate condition

Leaf wetness duration (LWD) measurements are required for disease warning in several agricultural systems, since it is an important variable for the diagnose of plant disease epidemiology. The cylindrical sensor is an inexpensive and simple electronic LWD sensor initially designed to measure this variable for onions, however some studies show that it may be helpful for standard measurements in weather stations and also for different crops. Therefore, the objective of this study was to assess their performance under tropical climate conditions, in Brazil, having as standard measurements those obtained by flat plate sensors, which have presented very good performance when compared with visual observations. Before field assessments, all LWD sensors used in our study (flat plates and cylinders) were white latex painted and submitted to a heat treatment. Laboratory tests were performed in order to determine the resistance threshold for the sensor to be considered wet and the time response of the sensors to wetness. In the field, all cylindrical sensors were initially deployed horizontally 30-cm above a turfgrass surface in order to assess the variability among them with respect to LWD measurements. The variability among the horizontal cylindrical sensors was reduced by using a specific resistance threshold for each sensor. The mean coefficient of variation (CV) of LWD data measured by the cylindrical sensors was 9.7%. After that, the cylindrical sensors were deployed at five different angles: 0º, 15º, 30º, 45º, and 60º. Data of measurements made at these angles were compared with the standard measurement, obtained by flat plate sensors at the same height and installed at 45º. The deployment angle had no systematic effect on LWD measurements for the local tropical conditions, since the correlations between flat plate and elevated cylinder measurements were very high (R² > 0.91), which differed from the results obtained under temperate climatic conditions, where LWD measured by cylinders were two hours longer than by flat plate sensors.

Medidas da duração do período de molhamento (DPM) são necessárias para diversos sistemas de alerta fitossanitário, uma vez que a DPM é uma variável importante para a epidemiologia. O sensor cilíndrico é um sensor eletrônico barato e que pode ser facilmente produzido. Esse sensor foi inicialmente projetado para medir DPM em cebola, contudo alguns estudos indicam que ele também pode ser utilizado em estações meteorológicas e outras culturas. Portanto, o objetivo deste estudo foi avaliar o desempenho de sensores cilíndricos sob condições tropicais, no Brasil, tendo-se as medidas obtidas pelo sensor de placa como referência. Antes de serem instalados no campo, todos os sensors eletrônicos utilizados no estudo (placa e cilíndricos) foram pintados com tinta latex branca e, em seguida, submetidos a tratamento térmico. Testes de laboratório foram realizados para determinar um limiar de resistência, a partir do qual os sensores seriam considerados molhados, e o tempo de reposta dos sensores ao molhamento. No campo, todos os sensores foram inicialmente instalados na horizontal a 30 cm de altura sobre gramado, visando a avaliar a variabilidade entre os sensores de DPM. A variabilidade entre os sensores cilíndricos na horizontal foi reduzida com a adoção de um limiar de resistência específico para cada sensor. O coeficiente médio de variação para DPM diária medida pelos sensores cilíndricos foi igual a 9,7%. Posteriormente, os sensores cilíndricos foram instalados em 5 ângulos diferentes com a horizontal: 0, 15, 30, 45, and 60º. As medidas obtidas por esses sensores são comparáveis com a medida padrão, fornecida por sensores de placa instalados a 45º e mesma altura. A mudança do ângulo de instação não teve efeito sistemático sobre as medidas da DPM para as condições locais, uma vez que as correlações entre as medidas dos sensores de placa e sensores cilídricos inclinados foram bastante elevadas (R² > 0,91), o que difere dos resultados obtidos em condições de clima temperado, onde a DPM medida pelo sensor cilíndrico foi duas horas mais longa do que a medida pelo sensor de placa.

Performance of cylindrical leaf wetness duration sensors in a tropical climate condition

Leaf wetness duration (LWD) measurements are required for disease warning in several agricultural systems, since it is an important variable for the diagnose of plant disease epidemiology. The cylindrical sensor is an inexpensive and simple electronic LWD sensor initially designed to measure this variable for onions, however some studies show that it may be helpful for standard measurements in weather stations and also for different crops. Therefore, the objective of this study was to assess their performance under tropical climate conditions, in Brazil, having as standard measurements those obtained by flat plate sensors, which have presented very good performance when compared with visual observations. Before field assessments, all LWD sensors used in our study (flat plates and cylinders) were white latex painted and submitted to a heat treatment. Laboratory tests were performed in order to determine the resistance threshold for the sensor to be considered wet and the time response of the sensors to wetness. In the field, all cylindrical sensors were initially deployed horizontally 30-cm above a turfgrass surface in order to assess the variability among them with respect to LWD measurements. The variability among the horizontal cylindrical sensors was reduced by using a specific resistance threshold for each sensor. The mean coefficient of variation (CV) of LWD data measured by the cylindrical sensors was 9.7%. After that, the cylindrical sensors were deployed at five different angles: 0º, 15º, 30º, 45º, and 60º. Data of measurements made at these angles were compared with the standard measurement, obtained by flat plate sensors at the same height and installed at 45º. The deployment angle had no systematic effect on LWD measurements for the local tropical conditions, since the correlations between flat plate and elevated cylinder measurements were very high (R² > 0.91), which differed from the results obtained under temperate climatic conditions, where LWD measured by cylinders were two hours longer than by flat plate sensors.

Medidas da duração do período de molhamento (DPM) são necessárias para diversos sistemas de alerta fitossanitário, uma vez que a DPM é uma variável importante para a epidemiologia. O sensor cilíndrico é um sensor eletrônico barato e que pode ser facilmente produzido. Esse sensor foi inicialmente projetado para medir DPM em cebola, contudo alguns estudos indicam que ele também pode ser utilizado em estações meteorológicas e outras culturas. Portanto, o objetivo deste estudo foi avaliar o desempenho de sensores cilíndricos sob condições tropicais, no Brasil, tendo-se as medidas obtidas pelo sensor de placa como referência. Antes de serem instalados no campo, todos os sensors eletrônicos utilizados no estudo (placa e cilíndricos) foram pintados com tinta latex branca e, em seguida, submetidos a tratamento térmico. Testes de laboratório foram realizados para determinar um limiar de resistência, a partir do qual os sensores seriam considerados molhados, e o tempo de reposta dos sensores ao molhamento. No campo, todos os sensores foram inicialmente instalados na horizontal a 30 cm de altura sobre gramado, visando a avaliar a variabilidade entre os sensores de DPM. A variabilidade entre os sensores cilíndricos na horizontal foi reduzida com a adoção de um limiar de resistência específico para cada sensor. O coeficiente médio de variação para DPM diária medida pelos sensores cilíndricos foi igual a 9,7%. Posteriormente, os sensores cilíndricos foram instalados em 5 ângulos diferentes com a horizontal: 0, 15, 30, 45, and 60º. As medidas obtidas por esses sensores são comparáveis com a medida padrão, fornecida por sensores de placa instalados a 45º e mesma altura. A mudança do ângulo de instação não teve efeito sistemático sobre as medidas da DPM para as condições locais, uma vez que as correlações entre as medidas dos sensores de placa e sensores cilídricos inclinados foram bastante elevadas (R² > 0,91), o que difere dos resultados obtidos em condições de clima temperado, onde a DPM medida pelo sensor cilíndrico foi duas horas mais longa do que a medida pelo sensor de placa.

Estimating leaf wetness duration over turfgrass, and in a 'Niagara Rosada' vineyard, in a subtropical environment

Leaf wetness duration (LWD) is a key parameter in agrometeorology because it is related to plant disease occurrence. As LWD is seldomly measured in a standard weather station it must be estimated to run warning systems for schedule chemical disease control. The objective of the present study was to estimate LWD over turfgrass considering different models with data from a standard weather station, and to evaluate the correlation between estimated LWD over turfgrass and LWD measured in a 'Niagara Rosada' vineyard, cultivated in a hedgerow training system, in Jundiaí, São Paulo State, Brazil. The wetness sensors inside the vineyard were located at the top of the plants, deployed at an inclination angle of 45º and oriented southwest, with three replications. The methods used to estimate LWD were: number of hours with relative humidity above 90% (NHRH > 90%), dew point depression (DPD), classification and regression tree (CART) and Penman-Monteith (PM). The CART model had the best performance to estimate LWD over turfgrass, with a good precision (R² = 0.82) and a high accuracy (d = 0.94), resulting in a good confidence index (c = 0.85). The results from this model also presented a good correlation with measured LWD inside the vineyard, with a good precision (R² = 0.87) and a high accuracy (d = 0.96), resulting in a high confidence index (c = 0.93), showing that LWD in a 'Niagara Rosada' vineyard can be estimated with data from a standard weather station.

A duração do período de molhamento (DPM) é uma variável agrometeorológica chave para a ocorrência de doenças de plantas. Como a DPM é raramente medida nas estações meteorológicas, ela deve ser estimada quando se pretende empregar sistemas de alerta de controle químico. Desse modo, o objetivo do presente estudo foi avaliar a estimativa da DPM sobre gramado por diferentes modelos a partir de dados meteorológicos obtidos em uma estação meteorológica padrão e verificar as relações entre a DPM estimada para o gramado e a medida em um vinhedo de 'Niagara Rosada', conduzido em espaldeira, em Jundiaí, SP, Brasil. Os sensores de molhamento no vinhedo foram instalados no topo das plantas com um ângulo de inclinação de 45º e com a face superior do sensor voltada para sudoeste, com três repetições. Os quatro modelos de estimativa da DPM foram: número de horas com umidade relativa do ar acima de 90% (NHUR > 90%), depressão do ponto de orvalho (DPO), árvore de classificação e regressão (CART) e o de Penman-Monteith (PM). O modelo CART estimou melhor a DPM no gramado, apresentando uma boa precisão (R² = 0,82) e uma ótima exatidão (d = 0,94), resultando num bom índice de confiabilidade (c = 0,85). Esta estimativa também apresentou uma boa correlação com a DPM medida no interior do vinhedo, com uma precisão razoável (R² = 0,87) e uma ótima exatidão (d = 0,96), resultando num ótimo índice de confiabilidade (c = 0,93), o que permite concluir que é possível estimar a DPM no vinhedo de 'Niagara Rosada' por meio de dados medidos ou estimados na estação meteorológica padrão.

Spatial variability of leaf wetness duration in cotton, coffee and banana crop canopies

Despite the importance of leaf wetness duration for plant disease epidemiology, there has been little attention paid to research on how its variability relates to different cropping situations. The objective of this study was to evaluate the spatial variability of leaf wetness duration (LWD) in three crops, comparing these measurements with turfgrass LWD, obtained in a standard weather station. LWD was measured by electronic sensors in three crops with different canopy structures and leaf area: cotton, coffee and banana. For the cotton crop, cylindrical sensors were deployed at the lower third and on the top of the canopy, facing southwest. For the coffee crop, flat plate sensors were installed in the lower third of the canopy facing northeast and southwest; in the middle third facing northeast and southwest; and inside and on the top of the canopy. For the banana canopy, cylindrical sensors were used to measure LWD in the lower third of the canopy and in the upper third of the plant. Turfgrass LWD was simultaneously measured in a nearby standard weather station. The LWD showed different patterns of variation in the three crop canopies. For coffee plants, the longest LWD was found in the lower portions of the canopy; for the banana crop, the upper third of the canopy showed the longest LWD; whereas for the cotton crop no difference was observed between the top and lower third of the canopy. Turfgrass LWD presented a good relationship with LWD measured on the top or in the upper third of the crops. Thus, the estimate of crop LWD can be perfomed based on turfgrass LWD, this being a useful tool for plant disease management purposes for crops in which the longer LWD occurs at the upper canopy portion.

Apesar da importância da duração do período de molhamento para a epidemiologia de doenças de plantas, pouca atenção tem sido dada à sua variabilidade em diferentes posições da cultura. O objetivo deste estudo foi avaliar a variabilidade espacial da duração do período de molhamento (DPM) em três culturas, comparando-se as medidas obtidas com a DPM medida sobre gramado em um posto meteorológico padrão. A DPM foi medida por sensores eletrônicos em três culturas com diferentes estruturas de dosséis e áreas foliares: algodão, café e banana. Na cultura do algodão, os sensores cilídricos foram instalados no terço médio e no topo do dossel voltados para o sudoeste. Na cultura do café, sensores de placa foram instalados no terço inferior do dossel voltados para nordeste e sudoeste; no terço médio também voltados para nordeste e sudoeste; no interior e no topo do dossel. Na cultura da banana, sensores cilíndricos foram instalados nos terços inferior e superior da planta. A DPM sobre gramado foi simultaneamente medida em um posto meteorológico próximo às culturas. A DPM exibiu diferentes padrões de variação nas três culturas. Para o cafeeiro, a DPM mais longa foi observada nas partes mais baixas da planta; para a bananeira, o terço superior foi o que apresentou a maior DPM; enquanto que para a cultura do algodão não houve diferença entre o topo e o interior do dossel. A DPM medida sobre gramado apresentou boa correlação com a DPM medida no topo ou no terço superior das culturas. Dessa forma, pode-se estimar a DPM nas culturas a partir da DPM do gramado, sendo esta uma ferramenta muito útil para o manejo de doenças de plantas em culturas onde a DPM mais longa ocorre nas porções superiores do dossel.