Fusarium Bosporus f. sp. cucumerinum is the fungal pathogen responsible for Fusarium vascular wilt of cucumber. The options for managing Fusarium wilt in greenhouse cucumbers are limited by our poor understanding of the modes of survival and dissemination of the pathogen. Aerial dissemination of the pathogen was investigated following the development of a highly specific and sensitive quantitative real-time PCR assay that reliably detected as few as 100 Fusarium oxysporum f. sp. cucumerinum genome copies in environmental matrices. Numbers of both macroconidia and microconidia were variable in greenhouse air samples at different times of day. A potential relationship between fluctuation in relative humidity and spore number was found. While this shows that the pathogen can be aerially disseminated, airborne spores were unable to infect wound stem sites. These results suggest that aerial inoculum propagates and disseminates the pathogen, but that infection is primarily through the root after aerial spores are deposited on the soil surface. Aerial dissemination was also found to occur through insect vectors. Sciarid and shore flies could carry between 1 × 102 and 1 × 106 pathogen genome copies/individual. Experimentally, sciarid and shore flies acquired F. oxysporum f. sp. cucumerinum following exposures to agar cultures of the pathogen of up to 94 hours and were found to transfer the pathogen, resulting in disease expression in a glasshouse transmission trial
