Dactylaria higginsii, a Fungal Bioherbicide Agent for Purple Nutsedge (Cyperus rotundus)

Ten different fungi recovered from diseased purple nutsedge and yellow nutsedge plants collected in several locations in Florida and southeastern United States were screened for pathogenicity to purple nutsedge (Cyperus rotundus) plants. Only Dactylaria higginsii, recovered from diseased purple nutsedge plants collected in Gainesville, caused disease in greenhouse trials. Based on the results of pathogenicity and host-range tests conducted in a greenhouse, D. higginsii was determined to have potential as a bioherbicide agent for purple nutsedge. It was highly pathogenic to purple nutsedge, yellow nutsedge (C. esculentus), annual sedge (C. compressus), globe sedge (C. globulosus), rice flatsedge (C. iria), and green kyllinga (Kyllinga brevifolia [=Cyperus brevifolius]). Initial symptoms on inoculated plants consisted of moist, dark-brown leaf spots that appeared 4 days after inoculation. The spots later coalesced into larger lesions and blotches, killing the leaves and sometimes the entire aerial parts. The fungus sporulated on the infected leaves and caused secondary infections on the emerging leaves and shoots within 20 to 28 days after inoculation. Inoculation with conidial suspensions of D. higginsii resulted in significant reductions in shoot numbers (72%), shoot dry weight (73%), and tuber dry weight (67%) of greenhouse-grown purple nutsedge plants 45 days after inoculation. The fungus did not infect any of the crop plants or weedy grasses (Poaceae) tested.