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Integrated Management of Sudden Wilt in Melons, Caused by Monosporascus cannonballus, Using Grafting and Reduced Rates of Methyl Bromide

Sudden wilt of melons induced by Monosporascus cannonballus is a worldwide problem, mainly in arid and semi-arid regions. Soil disinfestation by fumigation with methyl bromide is a common and very effective treatment for disease control. However, methyl bromide is expected to be banned from use within the next 5 to 10 years; therefore, alternative measures for disease management are urgently needed. In this study, the efficacy of methyl bromide at a reduced rate (15 g/m² instead of 50 g/m²) and grafted plants, alone or in combination, was examined. Experiments were conducted in the 'Arava region in southern Israel in naturally infested fields. First, various rootstock accessions were tested in three experiments. Of the eight rootstocks evaluated, cv. Brava (Cucurbita maxima) was selected to serve as a rootstock in the subsequent experiments due to its effects on wilt reduction (63 to 100% reduction in two experiments and 35% reduction in one experiment) and its horticultural performance. Next, integration of grafting and a reduced rate of methyl bromide was tested in two experiments. The reduced methyl bromide rate suppressed disease, but results were variable (32 and 91% reduction in the two experiments). Grafting, when used alone, significantly reduced wilt incidence by 84 to 87% compared to untreated plots. Integration of the two control measures provided adequate and reliable results and wilt incidence was always significantly lower (75 to 100% reduction) than incidence in untreated plots. Because control by each measure alone varies, integrated application is preferable.