Diagnosis and association of Olpidium bornovanus and MNSV with vine decline of melon in Honduras

Thirty soil samples, from 6 different farms with vine decline symptoms, plus two peat samples from a nursery were collapsed plants were previously sown, were analyzed for presence of organisms associated with the disease. With a soil-dilution plating method, only Macrophomina phaseolina and Acremonium were detected, in 2 samples each fungus. With a melon bait plant technique, named "soil phytopathometry", Olpidium bornovanus often together with Melon necrotic spot virus, was found in 70% of all the samples, corresponding with all the farms studied and the peat. Other pathogens that were detected less frequently included Monosporascus cannonballus (3.3%) and Rhizoctonia solani (3.3%). No Plectosporium tabacinum neither Rhizopycnis vagum (other two fungi associated with vine decline) were detected. Fusarium solani, that was detected very frequently (87%), was not associated with disease occurrence after a pathogenicity test. Consequently, O. bornovanus and MNSV were uniquely associated with disease occurrence and thus are the most probable cause of melon vine decline in the fields studied.