"Phytophthora root rot likes wet conditions and can have a major effect on yield," he said. "The spears rot under the surface and don't appear, so it's easy to underestimate the extent of the problem. It also causes establishment failures and post-harvest losses. From a breeder's point of view, it's a difficult pathogen to deal with. It reproduces sexually several times a season, so single-gene resistance would soon be overcome," he explained.
"A lot of Phytophthora is spread around on crowns. It's something that needs to be dealt with. Metalaxyl can double yield on an infected crop but it has no effect on Fusarium, so it's a diagnostic tool in that sense."
Asparagus virus 2 "makes crowns more susceptible to Fusarium", said Falloon. "It's everywhere. A lot of countries say they haven't got it but they haven't looked."
Dutch crown supplier and event sponsor Teboza said its plants are certified disease-free under the Naktuinbouw Select Plant quality mark.
Looking at global trends in asparagus production, Falloon said Peru is moving into other "more lucrative" crops, particularly table grapes, but in Mexico, with similar growing conditions, production has grown from 55,000 tonnes in 2008 to 140,000 tonnes last year.
Meanwhile, China "hasn't turned out to be a threat - food safety issues have kept the international market away", he added.
Internationally he noted a trend away from loose bunches. "Packaging lets you tell the story and how to prepare it. You can also sell less asparagus for a higher price."
Overall, he said: "There are opportunities for breeders to bring new varieties to growers. But with takeovers and reduced public funding there are fewer breeding programmes. Asparagus breeders are becoming an endangered species."