Resident fungal pathogens of common teasel ( Dipsacus fullonum ) in the province of Buenos Aires, Argentina: can they be used as biological control agents?

Abstract

Dipsacus fullonum (common teasel) is an invasive plant that hasbecome a problematic weed in Argentina. Biological controlusing resident natural enemies is considered an option thatdeserves to be explored. To this end, a survey of fungalpathogens was conducted in part of its invaded range, theprovince of Buenos Aires. Following visits to 50 populationsacross the province, seven fungal species were isolated fromdiseased common teasel plants, and their pathogenicity wasconfirmed: four leaf spot fungi (Alternaria sp.; Ascochyta dipsaci;Boeremia exigua and Cercospora elongata) and three soil bornefungi (Sclerotinia sclerotiorum producing white mould; and twobinucleate Rhizoctonia spp. producing root rot). Some of thesepathogens represent new host associations, new geographicrecords, or both. Cercospora elongata was found in 62% of thesurveyed sites, making it the most widespread pathogendetected on common teasel. Based on observed plant damage,presumed host specificity, geographic distribution, and ease ofmanipulation under laboratory conditions, C. elongata appearsto be the most promising candidate and is proposed forthe biological control of the weed in Argentina. However,observations from both laboratory and field studies suggest thatthe disease alone may not provide sufficient control, even afterincreased inoculum loads in the field. Therefore, incorporating C.elongata into an integrated management strategy isrecommended and discussed. These findings contribute to theknowledge of the diseases of common teasel and represent animportant first step towards the implementation of biologicalcontrol for this invasive species in Argentina.