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88 SEEDWORLD.COM DECEMBER 2015 Unfortunately D. bryoniae has developed some resist- ance to fungicide. University of Florida plant pathologists Nicholas Dufault and Mathews Paret have been working together with collaborators in China in an effort to understand the evolution of fungicide resistance in D. bryoniae in the United States. We are working with our Chinese collaborators to try and understand how pathogens can move through watermelon seed worldwide and how the movement of isolates from one region to another can influence fungicide resistance in the United States Paret says. Most of the watermelon seeds used in U.S. production systems are imported from six countries one of which is China. D. bryoniae is known as a seed borne pathogen and Dufault and Paret are trying to understand where it comes from and what the future risks might be from increased fungicide resistance. Paret Dufault and other Florida colleagues are also investigating the possibility of another seedborne dis- ease in watermelon caused by Pseudomonas syringae. For the first time in the spring of 2013 a massive out- break of P. syringae occurred in watermelon in Florida. Our first thought was that this looked like angular leaf spot of cucurbits but what we found out was that we had a huge influx of a strain of Pseudomonas that is genetically different from angular leaf spot of cucurbits that can infect watermelons squash Kamloops and pumpkin Paret says. We are looking at where this Pseudomonas syringae strain is coming from. Working with a seed company in the Netherlands we have learned that this strain of P. syringae is seedborne in zucchini there. We are working to see at what level our strains could potentially be seedborne. Researchers in Florida are also looking at water and transplant houses as potential sources of pathogenic inoculums. It is always important to know where your inocu- lum source is coming from says Jeffrey Jones director of the Southern Plant Diagnostic Network at the University of Florida. If the inoculum is coming from vegetative material seed or is just endemic to the location the source is a concern and needs to be eliminated. The mission of the Southern Plant Diagnostic Network is to enhance national agricultural security by quickly detecting introduced pests and pathogens. This is achieved through a functional nationwide net- work of public agricultural institutions with a cohesive distributed system to quickly detect high consequence biological pests and pathogens into U.S. agricultural and natural ecosystems by providing means for quick identifications and establishing protocols for immedi- ate reporting to appropriate responders and decision- makers. The goal of the network is to support a secure regional network for the detection and diagnosis of plant health problems extend and support sound public notices implement rapid and accurate diag- noses and response strategies and provide leadership and training. New virulent varieties of pests are constantly evolving D.P. Weber and others of Exeter University wrote last year in Global Ecology and Biogeography. Their emer- gence is favored by increased sizes of pest populations and their rapid life cycles Hope lies in the implementation of robust plant protection strategies and biosecu- rity measures particularly in the developing world. Whether such precautions can slow or stop this process remains to be seen the authors report. DID YOU KNOW New and virulent varieties of pests are constantly evolving and researchers at the University of Floridas Emerging Pathogens Institute are working to knock them out. More than one-tenth of all pests have reached more than half the countries that grow their hosts Weber says. If current trends continue many important crop producing countries will be fully saturated with pests by the middle of the century. While dispersal increases with host range overall fungi have the narrowest host range but are the most widely dispersed group Weber says. The global dispersal of some pests has been rapid but pest assemblages remain strongly regionalized and follow the distri- butions of their hosts. Erica Goss plant pathologist specializing in pathogen genetics at the University of Florida and a team of scientists have been study- ing the global spread of species of Xanthomonas gardneri which The global dispersal of some pests has been rapid but pest assemblages remain strongly regionalized and follow the distributions of their hosts. D.P. Weber