Influence of temperature and wetness period on infection of cherry and peach foliage byWilsonomyces carpophilus¹

Abstract

The effects of temperature and wetness duration on infection of sweet cherry (Prunus avium L.) and peach (Prunus persica L.) by Wilsonomyces carpophilus (Lev.) Adaskaveg, Ogawa & Butler were determined under controlled conditions. Young foliage of cherry seedlings and peach trees was inoculated with a conidial suspension of W. carpophilus and subjected to wetness periods of 0-24 h at temperatures of 5-30°C. On cherry, disease severity increased with wetness duration at each temperature tested, e.g., at 15°C, severity increased from no lesions at wetness durations < 1 h to 0.1, 1.9, 6.8, and 9.1 lesions/cm 2 after 6, 12, 18, and 24 h, respectively. After 24 h of wetness, the maximum disease severity of 10.5 lesions/cm 2 was obtained at 20°C. Although severity values were different, the general responses to temperature and wetness period were similar on peach. Multiple-regression equations using temperature and wetness duration as independent variables adequately described infection of cherry and peach foliage. The incubation period on cherry was 2, 2, and 3 d at 5, 15, and 25°C, respectively, while the latent period was 6 d at 15-25°C.

Leaf-wetness duration and temperature required for infection of saskatoon leaves byEntomosporium mespiliunder controlled 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).…”

“…Empirically determined relationships between environmental factors and disease have been used to time fungicide sprays for many diseases (Grove 2002;Thompson and Jenkins 1985). Therefore, management of entomosporium leaf and berry spot disease should depend on knowledge of the environmental conditions that promote pathogen infection and development.…”

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).…”

The development of a dynamic diseaseforecasting model to controlEntomosporium mespilionAmelanchier alnifolia

“…Therefore, to account for these variables, several regression equations could be integrated to describe the interactions between the pathogen and each component of its environment. Once a disease-forecast model has been constructed, it must be validated by comparing observed symptom development from laboratory and (or) field evaluation trials against predicted values that have been generated by regression models (Asher and Williams 1991;Grove 2002;Pfender 2003).…”