Host range and virulence of a fungal pathogen for control of giant salvinia (Salvinia molesta)

Authors: Boyette, Clyde; Hoagland, Robert; HIGGENBOTHAM, LAURENCE - Louisiana Technical University; WALKER, HARREL - Louisiana Technical University; YOUNG, JAMES - Louisiana Technical University; Stetina, Kenneth - Ken

Submitted to: American Journal of Plant Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/28/2021
Publication Date: 3/31/2021
Citation: Boyette, C.D., Hoagland, R.E., Higgenbotham, L.R., Walker, H.L., Young, J.A., Stetina, K.C. 2021. Host range and virulence of a fungal pathogen for control of giant salvinia (Salvinia molesta). American Journal of Plant Sciences. 12:444-454. https://doi.org/10.4236/ajps.2021.123029.
DOI: https://doi.org/10.4236/ajps.2021.123029

Interpretive Summary: Giant salvinia (Salvinia molesta) is an exotic, invasive, aquatic fern, native to Brazil and Argentina and, through accidental release, has now invaded most of the southern U.S. states. Due to its prolific growth rate, control with conventional weed control measures is often inadequate. We found that a mycelial formulation of the fungus Botryosphaeria rhodina (Br) effectively controlled this weed under greenhouse and field conditions. A surfactant (Silwet L-77) incorporated in the fungal formulation was essential for Br to infect and kill plants. Infection and mortality occurred rapidly (within 48 h after inoculation) and re-growth of treated plants did not occur. A dew period was not required to achieve infection and mortality of inoculated plants. Host range tests revealed that Br also infected other plants, such as common salvinia, red Azolla, and duckweed. However, no symptomatology was observed on several economically important crop species, such as rice, corn, and several important woody species such as bald cypress and loblolly pine that often occur in areas where giant salvina occurs and be subject to contact with releases of Br. In field trials, Br controlled giant salvinia ~ 95%. These results suggest that this isolate of Botryosphaeria rhodina (Br) has potential as a bioherbicide for controlling this problematic aquatic weed.

Technical Abstract: A teleomorph of the fungus Botryosphaeria rhodina (Berkeley et Curtis) von Arx, (Br) was evaluated as a bioherbicide for control of giant salvinia (Salvinia molesta D.S. Mitchell) under greenhouse conditions and in small-scale field trials. We found that fungal mycelium was highly infective and could be rapidly produced (48 h) in soyflour-cornmeal liquid media contained in shake flasks or fermenters. A dew period was not required to achieve infection and mortality of inoculated plants. A surfactant (Silwet L-77, a polyalkyleneoxide modified heptamethyl-trisiloxane) incorporated in the fungal formulation was required for Br to infect and kill plants. Infection and mortality occurred rapidly (within 48 h after treatment), and re-growth of treated plants did not occur. In replicated field trials, Br controlled giant salvinia ~ 95%. Br also infected other plants, such as common salvinia (S. minima Baker), and Azolla filiculoides Lam., as determined in ongoing host range research. However, no symptomatology was observed on several economically important crop species, such as rice (Oryza sativa L.), corn (Zea mays L.), and several woody species such as bald cypress (Taxodium distichum L.) and loblolly pine (Pinus taeda L.) occurring in areas where giant salvina occurs that would be subject to contact with releases of Br. These results suggest that this teleomorph of Botryosphaeria rhodina has potential as a bioherbicide for controlling this onerous aquatic weed.