Phytoparasitica (1999) 27, 142-143

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S. Pivonia, R. Cohen, J. Kigel, J. Katan and Rachel Levite (1999)
Effect of soil temperature on the development of sudden wilt disease of melons
Phytoparasitica 27 (2), 142-143
20th Congress of the Israeli Phytopathological Society, February 15-16, 1999, Bet Dagan, Israel, lecture
Abstract: The sudden wilt disease of melons (also known as vine decline or melon collapse), in the Arava Valley of southern Israel has been reported also in various arid areas worldwide. The causal agent of the disease in the Arava Valley is mainly the fungus Monosporascus cannonballus. The severity and rate of disease progress seem to be related to the environmental conditions prevailing during the growing season. In general, the disease is more severe in the short and hot autumn growing season compared with the cooler spring season. The effect of temperature on wilting rate was evaluated in autumn and spring under field conditions. In all three autumn seasons studied, wilt incidence was 100% and plants collapsed before fruit maturation. In the spring seasons, however, prematuration wilt was observed in only one season out of three tested. In an experiment conducted in the winter-spring season, wilting rate of melons grown in heated soil was significantly higher than of melons grown in nonheated soil. Disease enhancement can be attributed to the effect of temperature on the pathogen, since heating methyl bromide-treated soil did not result in plant collapse. The optimal temperature for hyphal growth is 30°C . The temperature affects ascospore germination and penetration to melon roots. Incubating spores with melon roots at 32°C resulted in a high germination rate which started after 11 days, compared with low and delayed germination when spores and roots were incubated at 20°C. Root colonization by the pathogen in the spring growing seasons was 50%, 62 days after planting compared with 41 and 35 days after planting in melons grown in the autumn and in heated plots in the spring, respectively. Soil temperature seems to be an important environmental factor affecting disease progress, since temperature elevation increases fungal growth, spore germination and root penetration. The interpretation of temperature effect under field conditions is more complicated, since temperature may influence also other factors such as vegetative development and fruit maturation that affect symptom expression.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Database assignments for author(s): Jaacov Katan, Shimon Pivonia

Research topic(s) for pests/diseases/weeds:
environment - cropping system/rotation
population dynamics/ epidemiology

Pest and/or beneficial records:

Beneficial Pest/Disease/Weed Crop/Product Country Quarant.

Monosporascus cannonballus Melon (Cucumis melo) Israel