Augmentative releases of the pompom rust fungus Puccinia eupatorii, a biological control agent of Campuloclinium macrocephalum (pompom weed) in South Africa
Alana den Breeÿen
ARC-PPRI, Weeds Pathology Unit
First identified on pompom weed in South Africa in 2006, the pompom rust fungus Puccinia eupatorii is now widely dispersed on pompom weed throughout its invaded range. Despite its wide distribution, the late emergence of the rust fungus in the field limits the effectiveness of it as a biological control agent. In November 2013, an augmentative release strategy for pompom rust was implemented at field sites in Gauteng (Rietvlei Nature Reserve) and Mpumalanga (Barberton) provinces. Plots were inoculated during a different month and one plot was inoculated repeatedly on each inoculation date. Natural infection plots were treated as controls. Disease incidence ranged from 14-100% in Rietvlei and from 33-80% in Barberton. Average leaf severity was higher in Rietvlei compared to Barberton. Plant density decreased after each augmentative inoculation. At the end of the growing season no significant difference in disease incidence, disease severity and plant density could be detected between inoculated and natural infection plots at either site. Plants tagged at the start of the trial to evaluate the impact of augmented inoculations on pompom weed had died before measurements could be taken. It is too early in the trial for management recommendations to be given.