A Model Defining the Relationship Between Temperature and Leaf Wetness Duration, and Infection of Watermelon by Colletotrichum orbiculare

Abstract

Controlled environment experiments were conducted to determine the relationship between temperature, leaf wetness duration, and infection of watermelon by Colletotrichum orbiculare. Flats of watermelon seedlings were inoculated and exposed to various combinations of temperature (12, 15, 18, 21, 24, 27, and 30°C) and leaf wetness duration (2, 4, 8, 12, 16, and 24 h). The experimental design was a split-plot, with whole units represented by temperature and subunits represented by leaf wetness duration. Anthracnose incidence, defined as the percentage of symptomatic seedlings in each flat 10 days after inoculation, increased with increasing leaf wetness duration at all levels of temperature. The optimum temperature for infection ranged from 21 to 24°C. At most temperatures, as little as 2 h of leaf wetness was required for infection. Analysis of variance with orthogonal polynomial contrasts and multiple regression procedures was used to define the relationship of anthracnose incidence to temperature and leaf wetness duration.

Leaf-wetness duration and temperature required for infection of saskatoon leaves byEntomosporium mespiliunder controlled conditions

“…Similar relationships between temperature and leaf wetness have been well documented for a variety of plants and diseases (Evans et al 1992;Mathieu and Kushalappa 1993;Monroe et al 1997). Although the regression equation developed here applies to the controlled environmental conditions of the present study, it lays the foundation for the development of a model for fungicide spray scheduling under field conditions.…”

“…There was a large increase in disease development with duration of leaf wetness of 24 h. However, as our study did not look at leafwetness periods beyond 24 h, it was not possible to determine if 24 h was the optimal leaf-wetness period for infection of saskatoon. Similarly, studies of other pathogens (Grove 2002;Monroe et al 1997) and E. mespili on Photinia ×fraseri (Baudoin 1986a) also revealed a pattern of increased disease with increasing leaf wetness. In these studies, a period of 24 h was the longest duration examined.…”

“…Given the limitation in growth room resources, 24 h was selected as the maximum period of leaf wetness in accordance with other crop disease studies (Grove 2002;Monroe et al 1997). Moreover, leafwetness duration in Manitoba, which is one of the wetter areas of the Prairies, typically remains well below 24 h, based on our field monitoring (data not shown).…”

Estimating inoculum production relative to percent leaf area infected and environmental conditions required for stimulating release ofEntomosporium mespiliconidia onAmelanchier alnifolia

“…Thompson and Jenkins (1985) showed that a reduction in lesion area results in a lower number of Colletotrichum lagenarium (Pass.) conidia produced from infected leaves of Cucumis sativus L. Disease-forecasting models based on leaf-wetness duration and temperature (Grove 2002;Monroe et al 1997) can be integrated with a fungicide spray program to help reduce disease. A similar disease-forecasting model based on leafwetness duration and temperature for E. mespili on saskatoon was developed (Holtslag et al 2003).…”

Índice de favorabilidade agrometeorológica da ramulose (Coletotrichum gossypii pv. cephalosporioides) e da mancha angular (Xanthomonas axonopodis pv. malvacearum) do algodoeiro

“…Várias combinações de fitopatossistemas seguem este modelo, como a infecção de Stemphylium vesicarium em pêra (MONTESINOS et al, 1995); Alternaria cucumerina em melão rajado (EVANS; NYQUIST; LATIN, 1992); Colletotrichum orbiculare em melancia (Monroe et al, 1997) e Colletotrichum lindemuthianum no feijoeiro (DALLA PRIA, 1997).…”