Click on any
image for a more
detailed view

Significance

BFB has great potential to cause significant economic losses to cucurbit production, and has been responsible for up to 90% losses of marketable yield in some watermelon fields. BFB was first observed in 1965 on watermelon at the USDA plant introduction station, Griffin, GA, where it caused seedling blight symptoms. The disease was confined to seedlings at the station, suggesting that it was introduced by seeds of plant introductions. Furthermore, no outbreaks were reported in commercial watermelon fields during this period. By 1988, BFB outbreaks were observed in commercial watermelon fields in the Mariana Islands (in the North Pacific Ocean). In 1989 the first outbreak in the continental US was observed in Florida. It is clear now that the source of inoculum in the commercial watermelons was independent of the seedling blight outbreak at the USDA Plant Introduction Station in GA. Since 1989, BFB outbreaks have occurred sporadically in the major cucurbit-producing states in the US, with significant economic impact. Most notably, BFB caused significant losses in 1994 when the seedborne nature of the pathogen, along with the lack of adequate seed health assays, resulted in widespread outbreaks in Florida, Georgia, Indiana, South Carolina and Texas. These outbreaks brought national attention to BFB and highlighted the general threat posed by seedborne diseases. The repercussions of these outbreaks included direct economic losses, as well as costly lawsuits against seed and transplant producers. The economic magnitude of these lawsuits forced some seed companies out of business while others suspended watermelon seed sales in certain “high risk” states. Even today, some seed producers do not guarantee the performance of their seed in South Carolina for fear of litigation. Fortunately, with the implementation of routine seed health testing, many companies resumed the sale of watermelon seed with reduced risk of BFB transmission. Despite the implementation of routine seed health testing, sporadic BFB outbreaks continue to occur, and in 2000 and 2001 significant widespread outbreaks occurred across the US. Additionally, outbreaks have occurred on a wide range of cucurbit hosts in Australia, Brazil, China, Costa Rica, Israel, Japan, Nicaragua, Taiwan, and Thailand.

This wide geographical distribution of BFB indicates that seed is still an important primary inoculum source for BFB and suggests a need for improved management strategies.

To guard against costly lawsuits, seed producers now include a disclaimer with each watermelon seed package, stating that even though seeds have been tested, there is no guarantee that they are free of A. avenae subsp. citrulli. Additionally, at the time of seed purchase, growers are required to waive their rights [example of a watermelon seed purchase agreement (Figure 28)] to pursue legal action against seed producers in the event of a BFB outbreak.

RETURN TO TOP