Location: Foreign Disease-Weed Science ResearchTitle: Longevity of Uromyces transversalis, causal agent of Gladiolus Rust, under various environmental conditions
Submitted to: Plant Health Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2015
Publication Date: N/A
Interpretive Summary: Gladiolus rust is a fungal plant disease, regulated by the USDA, Animal and Plant Health Inspection Service, first discovered in the U.S. in 2006 in Florida and California. To better understand how to control the disease, we conducted a study to determine how long spores of the pathogen can survive in greenhouse and/or field soil under various environmental conditions. We determined that the pathogen could not survive past approximately 60 days under warm conditions and 70 days under cool temperatures, regardless of the moisture level in the soil. This indicated that the regulatory requirement for a 120 day host-free period following discovery of the disease is sufficient for eradication of the pathogen. Furthermore, it suggested that it is unlikely that the glad rust pathogen could survive in soil through the non-growing season. This information will be useful for state and federal agencies to further refine their regulatory guidelines for eradication of the pathogen from gladiolus growing areas.
Technical Abstract: To help determine if gladiolus rust might spread and become established in new areas of the U.S., we studied the effects of environment on longevity of U. transversalis urediniospores and disease development. Urediniospores were subjected to different temperatures and moisture in a factorial design. Treatments consisted of gladiolus leaf pieces with actively sporulating uredinia placed in mesh bags either in a plastic beaker without soil (dry) or plastic bags covered in damp soil (damp). These treatments were either held in a greenhouse at 22 to 26 degrees C (warm) or refrigerator maintained at 4 degrees C (cool). After 14 days, 59 percent of urediniospores maintained under warm, dry conditions were viable compared to only 1 percent maintained under warm damp conditions. After 56 days, viability dropped to 3 percent and near 0 percent, respectively. Under cool conditions, viability exhibited a different pattern. After 14 days, 1 percent of urediniospores germinated under cool, dry conditions versus 79 percent under cool damp conditions. By 13 weeks, germination dropped to 0.7 percent and 0 percent, respectively. It was concluded that it was unlikely that the glad rust pathogen could survive in soil through the non-growing season. In a second experiment in which growth chambers simulated temperatures in Florida, disease was not transmitted by corms from infected plants, or when healthy corms were planted into potentially contaminated soil.