Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/25/1995
Publication Date: N/A
Interpretive Summary: Soil-borne diseases have caused serious yield losses in the melon growing areas of California. Much speculation has centered around Monosparascus root rot/vine decline as the disease involved. However, considerable evidence shows the distribution of the Monosporascus root rot/vine decline disease is restricted to southern California. Acremonium collapse is more likely associated with the sudden collapse of melon vines in the central valleys of California. Accurate identification of the diseases and associated microorganism is paramount to develop proper control strategies.
Technical Abstract: Since the early 1980's, a root rot caused by an unknown pathogen has resulted in serious yield losses in cantaloupe and honeydew melons in California. Apparently-healthy plants wilted or declined within a period of 5-10 days as the melons approached maturity. A wide array of symptoms were encountered on the various cucurbits collected from affected fields. From the Sacramento Valley to the upper San Joaquin Valley (Colusa to Fresno Co.), an Acremonium sp. was commonly isolated from roots of symptomatic plants of cantaloupe, honey dew, squash, and watermelon. The symptoms were similar to a newly described disease in Spain called "Acremonium collapse". In the lower San Joaquin Valley and in the southern part of the state (Kern and Riverside Co.), Monosporascus cannonballus Pollack & Uecker was isolated from roots of collapsed cantaloupe and watermelon plants. The symptoms were essentially identical to those described in south Texas for "Monosporascus root rot/vine decline". Pathogenicity of ten selected isolates of each fungus was demonstrated on cantaloupe seedlings (cv. Magnum 45). After 28 days in the greenhouse, these two fungi produced symptoms that were identical to those produced by Spanish isolates of Acremonium sp. and Texas isolates of M. cannonballus. This is the first report of M. cannonballus in California, and the first report of an Acremonium sp. associated with a mature vine collapse of cantaloupe and watermelon in the United States.