Direct planting of infested seed results in BFB seedling transmission under ideal environmental conditions. BFB seedling transmission is heavily dependent on high relative humidity; hence the risk of disease outbreak is reduced with direct seeding. Increasingly, commercial cucurbit production involves transplanting greenhouse-grown seedlings to the field to ensure rapid plant stand establishment. Transplant house conditions including high temperatures, high relative humidity, and high plant populations are conducive to BFB seedling transmission and rapid disease spread (Figure 23) . The exact mechanism of BFB seedling transmission is unknown, but bacteria move from seed to seedling tissues where they multiply in intercellular spaces and initiate water-soaked lesions. Bacteria in lesions are dispersed by overhead irrigation to seedlings throughout transplant house facilities. Splash-dispersed bacteria initiate secondary infections that are responsible for rapid epidemic development and high populations of infected seedlings. Even in the absence of symptoms, epiphytic A. avenae subsp. citrulli populations may initiate BFB outbreaks under ideal field conditions. Because of these factors, the risk of BFB development is high, even for seedlots with low levels of contamination.