BASF agronomy manager Simon Townsend told the AGA conference that the two active ingredients of Signum - pyraclostrobin and boscalid - had been shown in trials to have physiological effects on the plants themselves.
Pyraclostrobin has been found to trigger the plant's own defence mechanisms against various pathogens the fungicide does not directly affect, while both active ingredients have been shown to inhibit ethylene production caused by stress.
Townsend said the effects had first been noticed with kresoxim-methyl, BASF's first strobilurin fungicide introduced a decade ago.
Signum is newly available for use on asparagus thanks to a SOLA issued in January.
ADAS plant pathologist Kim Green said there were three stobilurin fungicides available for Stemphylium but that resistance to other fungal species on other crops had been reported. "It is important to use them carefully to maintain their effectiveness," she said.