AN EFFECTIVE ASPARAGUS STEM BLIGHT MANAGEMENT PROGRAM

China is the largest asparagus production country in the world with cultivation areas totaling 120,000 hectares (2007 statistics). With demand increasing there is potential for additional plantings. Yet, there are many challenges for asparagus production in China. The main one is asparagus stem blight caused by Phomopsis asparagi that reduces yield and eventually loss of plants. In recent years, the infection rates of this disease in China have been averaging around 50% causing annual loss of around 14,000 hectares of plantings. Clearly, stem blight is a serious threat for asparagus industry of China.
A number of factors contribute to the wide spread of asparagus stem blight in China. The disease is readily proliferated by spores and mycelia. The spores can be efficiently spread by rain, irrigation, wind, and people. The rainy season in summer is particularly conducive to the proliferation of the disease as the splashing of rainwater facilitates the dissimilation of P. asparagi spores and the increase in humidity helps the initiation of infection. P. asparagi reproduces prolifically. It is quite common that within a growing season the pathogen can go through over ten sporulation and reinfection cycles. While the spores are susceptible to certain fungicides, the fungicides are ineffective against the spores while they are within the sporangia. Thus, fungicides are generally ineffective to break the reinfection cycles as the pathogen constantly sporulates throughout the rainy season. Worse yet, the spores are very persistent. After the growing season they can overwinter in the remnant of the leftover stalks or in the soil. Consequently, once a field is infected, it is virtually impossible to eliminate the pathogen from the field. Nevertheless, we have demonstrated that with diligent and intensive management it is possible to keep the infection under control. Here we briefly review the disease and report an effective, albeit very labor intensive, protocol for asparagus stem blight control.