Author
Melissa C. Smith
melissa.smith@usda.gov
USDA ARS Invasive Plant Research Laboratory
Fort Lauderdale
Coauthors
Carey R Minteer, University of Florida, Fort Pierce, USA
Abstract
Waterhyacinth (Pontederia crassipes, hereafter WH) is a persistent aquatic weed in Florida. Integrated Weed Management (IWM), utilising chemical, physical, and biological control or some combination thereof, is prioritised as a management tool. We established 3 x 3-meter floating plots (N= 6 per treatment) each containing WH and a mix of native vegetation within a 10-hectare pond. Additional tanks were filled with water from the pond and WH and treated to maintain insect-free plants. WH plots were treated with the herbicides Penoxsulam, and 2,4-D at operational rates in Florida. Native plant and WH cover, biomass, water nutrients and herbivores were surveyed every 30 days after treatment (DAT), ending at 120 DAT. Untreated plants in control tanks were significantly smaller than plants in the pond due to exhaustion of nutrients – tanks were not initially fertilized and water nutrients were significantly lower within the control tanks compared to the pond. In herbicide treatments within the pond, WH cover decreased until 60 DAT, and then increased. Biocontrol only increased native plant cover, and WH increased less than the 2,4-D treated plots. Biocontrol agent abundance was greatest for the insects only treatment, though the biocontrol agents recolonise plants sprayed with Penoxalam more quickly than 2,4-D. WH cover increased slower in the insect only treatment, with increases in native species. This study illustrates the importance of in-situ IWM studies for waterhyacinth.
keywords
Water hyacinth
Floating aquatic weeds
IWM
Inundative releases
Highlights
Penoxsulam resulted in faster agent recovery and less WH at the conclusion compared to 2,4-D.
Insect only treatments resulted in an increase in native plant cover and biomass.
Biological control could be integrated well with certain herbicides.