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

Abstract

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. Key words: dew, microclimate, plant disease, warning systems VARIABILIDADE ESPACIAL DA DURAÇÃO DO PERÍODO DE MOLHAMENTO FOLIAR NAS CULTURAS DO ALGODÃO, DO CAFÉ E DA BANANARESUMO: 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...

Reconsidering Leaf Wetness Duration Determination for Plant Disease Management

“…Other studies, such as by Sentelhas et al (58) and Santos et al (54), showed the same tendency. These results strengthen the idea that LWD could be measured near a crop canopy without having to install sensors in the canopy itself, and thereby avoid some of the variability inherent for in-field placements.…”

“…Most studies have indicated that maximum dew deposition occurs at approximately three-fourths of the canopy height (37,38,50). Spatial heterogeneity in profiles of LWD has been esti mated for maize, apple trees (2,58), banana (54), and soybeans (55). Figure 8 shows the spatial variability in LWD in an apple canopy resulting from dew events.…”

Irrigação Localizada E a Incidência Do Bicho-Mineiro Do Café

“…Dados estatísticos transformados em Log (x+0,5). al., 1996;Santos et al, 2008), o que pode ter desfavorecido o BMC. Esse fato possivelmente resultou em condições microclimáticas desfavoráveis ao BMC, devido o menor ressecamento das folhagens.…”

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

“…Al igual que en nuestro caso, estudios realizados en cítricos en Florida por Santillán et al (2009) no detectaron diferencias significativas en la duración de HF registrada por los sensores en los días con lluvia. Santos et al (2008) no detectaron diferencias en la duración de HF entre la parte alta y baja de las plantas de algodón. Sin embargo, en plantas de café encontraron que la duración de HF fue mayor en la parte más baja mientras que en plantas de plátano fue mayor en la parte alta.…”