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SPECIAL SESSION: Plant Pathologists of the Future: Showcasing Graduate Student Presentation Winners from APS Division Meetings

Spread of Verticillium wilt fungi through invasive Ailanthus altissima (tree-of-heaven) stands in Virginia, USA
Rachel Brooks - Virginia Tech. Antonius Baudoin- Virginia Tech, Scott Salom- Virginia Tech

Experiments in Pennsylvania, USA have indicated that two species of Verticillium wilt fungi have the potential to control the invasive tree-of-heaven (Ailanthus altissima). To determine which of four treatments (V. nonalfalfae, V. dahliae, a 1:1 ratio of both, and a control of water) are effective in warmer and cooler areas of Virginia, USA a randomized complete block design was set up in six A. altissima-dominated sites. One-fifth of the 2,717 mapped A. altissima stems were inoculated and monitored for two consecutive field seasons. The area under the disease progress curve (AUDPC) was calculated for both direct-inoculated stems and surrounding noninoculated stems, and analyzed using linear regression methods. Similar to previous results, V. nonalfalfae in combination or alone caused the most disease in direct-inoculated stems, followed by V. dahliae. Only V. nonalfalfae in combination or alone was confirmed spreading to healthy A. altissima. Representative climate and stand metrics were included in a model selection process to determine if any variables may limit success of these treatments. An increase in the average diameter at breast height was associated with reduced AUDPC values in stems inoculated with V. dahliae, while no stand or climate variables influenced disease spread. These results indicate that V. nonalfalfae may be an effective biocontrol in warmer areas of A. altissima’s range, beyond where V. nonalfalfae has been formerly found impacting A. altissima.