Submitted to: European Plant Protection Organization Bulletin
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/31/1999
Publication Date: 12/18/2000
Interpretive Summary: Spain produces 42,000 hectares of melons with considerable export to European markets. In the last ten years, melon production in Spain has decreased more than 40% due to collapse of the vines caused by soilborne diseases. A systematic study of the fungi involved in vine collapse demonstrated that Acremonium collapse was the predominant disease of melons sin Spain. Although Monosporascus vine decline is generally associated wit hot semi-arid environments, the disease increased in prevalence over the ten year study. Melon collapse in Spain is similar to the disease complex in the United States with several fungi capable of causing collapse of the vines. Since these are two emerging diseases in melon production areas of the United States, monitoring of spread and severity are essential to our knowledge base.
Technical Abstract: In the last ten years, melon cultivated areas in Spain have decreased more than 40% due to collapse of the vines caused by soilborne diseases. Spain produces 42000 hectares of melons with considerable export to the European markets. Important economic losses have resulted. In order to better understand the etiology of this disease, a survey of 217 melon fields throughout all melon production areas of Spain was conducted from 1987 through 1996 to analyze the fungal root population. In addition, the presence of melon necrotic spot virus (MNSV) which is present mainly in south-eastern Spain was noted. The predominant fungal species isolated from 82.5% of sampled fields with symptoms of collapse was Acremonium cucurbitacearum. Roots affected by this fungus show corky brown areas soon after transplanting. Small secondary roots and root hairs become necrotic, although there is a continuous production of new rootlets. This process continues until the late stages of the disease. Finally, when fruits approach maturity the entire plant wilts and dies. Other fungal species associated with melon collapse are: Monosporascus cannonballus (isolated from 29.5% of sampled fields), Macrophomina phaseolina (32.7%), Pythium spp. (31.8%) and Rhizoctonia solani (31.8%). From among these, the incidence of M. cannonballus isolated from diseased melons has increased substantially over the past ten years. In summary, melon collapse in Spain is complex since several fungi capable of causing collapse of the vines are prevalent and often isolated from roots in the same field. In addition, other minor pathogens such as Rhizopyenis vagum and Plectosporium tabacinum are frequently isolated from symptomatic vines and may also contribute to the death of the plants.