An Optical Leaf Wetness Sensor

Griffioen, H.; Kornet, J.G.; Schurer, K.

doi:10.17660/actahortic.1992.304.13

Cited by 32 publications

(4 citation statements)

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“…Since such sensors are developed for use on a particular material, e.g. leaf wetness sensors are designed so that the wetting and drying of the sensor is similar to the wetting and drying of the leaf (Davis and Hughes 1970;Griffioen et al 1992), they might give inaccurate results if used on a material with different surface properties. This was experienced by Bernardi et al (2006) who found that leaf wetness sensors used on glass surfaces registered longer wetness periods than their own sensor which measured directly on the glass surface.…”

Section: Discussionmentioning

confidence: 99%

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Methods for determination of duration of surface moisture and presence of water in gaps in wood joints

Fredriksson

Wadsö²,

Johansson³

2013

Wood Sci Technol

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Link to publicationCitation for published version (APA): Fredriksson, M., Wadsö, L., & Johansson, P. (2013). Methods for determination of duration of surface moisture and presence of water in gaps in wood joints. Wood Science and Technology, 47(5), 913-924. DOI: 10.1007/s00226-013-0549-4 General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ABSTRACTIf water stays on wood surfaces or is trapped in gaps, the wood is supplied with water during a long period of time and high local moisture contents are reached. This can lead to decay by rot fungi and it is therefore important to avoid such water traps in order to limit the decay rate. This paper presents two methods; one for determination of duration of surface moisture on wood surfaces and one for determination of duration of water trapped in gaps in wood joints. Both these methods are based on similar electrical conductance measurements as are commonly used to measure moisture content of wood. Both sensor types consist of insulating tubing, electrically conductive adhesive and copper wire. The sensors monitor the presence of moisture on the actual material surface and because of their small size they do not influence the amount and duration of moisture that stays on the surface or in the gap.2

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Section: Discussionmentioning

confidence: 99%

“…Apart from these electrical sensors there are also mechanical types (see e.g. Wallin (1963)), beta-ray gauge sensors (Barthakur 1985;Bunnenberg and Kuhn 1977) and optical sensors (Zlochin and Seginer 2001;Griffioen et al 1992;Heusinkveld et al 2008). A review of different types of leaf wetness sensors was made by Huber (1992).…”

Section: Introductionmentioning

confidence: 99%

Methods for determination of duration of surface moisture and presence of water in gaps in wood joints

Fredriksson

Wadsö²,

Johansson³

2013

Wood Sci Technol

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“…Some authors have suggested a relative humidity threshold as surrogate for surface wetness (Sutton et al, 1984;Wilks & Shen, 1991). Peltier cooled dew point sensors can be an inexpensive and reliable method to determine relative humidity (Bailey, 1999;Griffieon et al, 1992;Vancauwenberghe et al, 1996), although dirt deposits on the mirror surface may compromise their performance (Griffieon et al, 1992). Vincelli and Lorbeer (1988) found that relative humidity could be used to estimate missing surface wetness data; however, several other studies have shown there is a relatively poor correlation between periods of high humidity and surface wetness (Francl & Panigrahi, 1997;Lomas & Shashoua, 1970;Wallin, 1963).…”

Section: Sensorsmentioning

confidence: 99%

Estimating Surface Wetness on Plants

Magarey

Seem

Weiss

et al. 2015

Agronomy Monographs

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“…Varios estudios sugieren umbrales de HR como estimador de la HF (Vincelli y Lorbeer, 1988;Griffieon et al, 1992;Gleason et al, 1994;Vancauwenberghe et al, 1996). En varios estudios se ha encontrado una correlación positiva entre la formación de la HF y la HR promedio (Shaw, 1973;Zangvil, 1996;Sentelhas et al, 2008).…”

Section: Discussionunclassified

Epidemiología de la mancha marrón de las mandarinas causada por Alternaria alternata. Desarrollo de estrategias de control eficientes

Bassimba¹

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Alternaria brown spot (ABS), caused by the 'tangerine' pathotype of Alternaria alternata, (Fr.) Keissl. is a serious disease in several mandarin cultivars such as 'Fortune', 'Nova' and other hybrids. Although the disease is widespread in the Mediterranean Basin, the epidemiology of the disease in semiarid conditions is unknown. Epidemiological studies were conducted during two consecutive years in Spain. The presence of inoculum was studies on leaves, twigs and fruit on affected trees, as well as weeds and leaf litter was determined. The dynamics of airborne conidia of Alternaria were studied with a spore trap and by exposing plates of the semi-selective medium ARSA. The effect of environmental factors in the incidence of ABS was studied through exposure of trap plants.Conidia of Alternaria were continuously detected throughout the period of study and pathogenic isolates were obtained in all sampling dates. However, the number of pathogenic isolates was not correlated with the total captured. Affected leaves and shoots were considered the main source of inoculum, with 15-76% of pathogenic isolates. Pathogenic isolates were also found in leaf litter and weeds of the genus Sonchus, but in very low proportion. The pathogen survived in fallen immature leaves for up to 76 days, coinciding with complete leaf litter decomposition. In contrast to humid areas, infections occurred mainly in spring and autumn, on weeks with rainfall ≥2.5 mm and average temperature ≥12.5°C. Based on quantile regression, the amount of rainfall, number of rain days, and total wetness duration were considered important factors increasing ABS incidence during infection periods.The infection efficiency of the pathogen was studied by inoculating plants of 'Fortune' and 'Nova' under different combinations of temperature (8-35°C) and wetness durations (8-48 hours). Data obtained from the infection efficiency study were fitted to generalised additive models (GAMs) and a generic infection model. Disease incidence significantly increased with leaf wetness duration over 16 hours. Disease incidence decreased with temperatures below 12°C or above 27°C. No infections were observed at 35ºC. The incidence of ABS did not Abstract increase after a dry period of one hour in 'Fortune' and two hours in 'Nova'. Post-infection temperature had a significant effect in the incubation period of the ABS pathogen, but maximum symptom expression was observed after no more than 30 hours in 'Fortune' and about 60 hours in 'Nova'. With GAMs models, disease incidence at low temperature was higher in 'Fortune' than in 'Nova'.The two infection models obtained, the Alter-Rater model developed in Florida and a simple rule system (SRS) based on temperature and rainfall were evaluated using independent infection data obtained from trap plants of 'Fortune' and 'Nova' exposed weekly in three orchards during 2011 to 2013 (n = 266). Model evaluation was performed using ROC curve analysis. Considering that the high sensitivity of the models is critical for the control of ABS, the partia...

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An Optical Leaf Wetness Sensor

Cited by 32 publications

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Methods for determination of duration of surface moisture and presence of water in gaps in wood joints

Methods for determination of duration of surface moisture and presence of water in gaps in wood joints

Estimating Surface Wetness on Plants

Epidemiología de la mancha marrón de las mandarinas causada por Alternaria alternata. Desarrollo de estrategias de control eficientes

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