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Data from: Toxicity of herbicides used for control of waterhyacinth in the California Delta towards the planthopper Megamelus scutellaris released for biological control

posted on 2024-02-20, 21:09 authored by Patrick MoranPatrick Moran

Data from five laboratory bioassays and three field mesocosm studies performed by Dr. Patrick Moran of the USDA-ARS Invasive Species and Pollinator Health Research Unit, to examine the toxicity of five herbicides (2,4-D, glyphosate, imazamox, penoxsulam and diquat) and two surfactants that are often applied with herbicides (a paraffinic-oil based one and a vegetable oil-based one) to the planthopper Megamelus scutellaris (Hemiptera: Delphacidae) released in the US for biological control of waterhyacinth (Eichhornia crassipes or Pontederia crassipes) an invasive floating aquatic weed. The studies were performed between 2016 and 2021 to support integrated management of waterhyacinth in the Sacramento-San Joaquin Delta of northern California. The planthopper has also been released in Florida and Mississippi, and in South Africa. Herbicide applications are often still necessary where this planthopper and other biocontrol agents have been released. The research question was 'can the planthopper survive exposure to the herbicides and surfactants?'. In lab bioassays, planthoppers from greenhouse colonies were exposed to herbicide-dipped leaves for 24 hours and then allowed to feed for six days on untreated plants. Planthoppers were then collected, frozen and counted. Exposure to diquat or the paraffinic oil-based surfactant caused 40% to 69% greater mortality than did exposure to water-dipped leaves in more than one trial, while the other four herbicides and the vegetable oil-based surfactant were not toxic. In field mesocosm tests, mesocosms were established in 21L tanks caged with mesh tents, and plants allowed to grow for 4 weeks. Between 150 and 240 adult planthoppers were then released into each mesocosm. The following day, mesocosms were sprayed with herbicide, surfactant or insecticide solutions or an insecticide positive control. Three days later, planthoppers were collected with vacuums, frozen and counted. Only treatment with the paraffinic oil-based surfactant reduced final counts (by 36% to 49%) in a manner that was statistically significant compared to water-sprayed mesocosms in more than one mesocosm field trial, along with the insecticide positive control (by up to 98%). Diquat reduced final counts by 64% in one trial. The results indicate that, with the possible exception of diquat, exposing planthoppers to herbicides does not cause significant mortality, consistent with prior regulatory evaluations of these herbicides as being safe for insects. A surfactant that is often applied with the herbicides is toxic to the planthopper, consistent with expectations that this surfactant, designed to break down plant waxes on leaf surfaces, is likely also harmful to insect cuticular waxes, which insects rely on to contain body fluids. Leaving unsprayed refuges for the planthopper may be a useful component of integrated waterhyacinth control programs.

Resources in this dataset:

Resource Title: Toxicity of herbicides and surfactants to the waterhyacinth planthopper Megamelus scutellaris.

File Name: Waterhyacinth planthopper herbicide toxicity data PMoran.csv

Resource Software Recommended: MS Excel,url:

Resource Title: Data dictionary for dataset on toxicity of five herbicides and two surfactants towards the planthopper Megamelus scutellaris.

File Name: Data dictionary for AgPub archive plain text.txt

Resource Software Recommended: Microsoft Word,url:


USDA-ARS: 2030-22000-032-00D


Data contact name

Moran, Patrick

Data contact email


Ag Data Commons

Intended use

For use by scientists and aquatic weed control practitioners who are interested in biological control and integrated management of waterhyacinth.

Use limitations

This dataset is associated with an unpublished manuscript that is currently (2023/02/14) in revision. Mention of active ingredients or trade names in the information here and in the paper (if and when published) are solely to convey specific information and does not imply an endorsement by the U.S. Department of Agriculture.

Temporal Extent Start Date


Temporal Extent End Date



  • Not specified

Geographic Coverage


Geographic location - description

Laboratory studies conducted at the USDA-ARS Western Regional Research Center, Invasive Species and Pollinator Health Research Unit, 800 Buchanan St., Albany, CA 94710. Field mesocosm studies conducted at the Putah Creek Ecosystem Center, University of Caliifornia-Davis, Davis, CA 95616

ISO Topic Category

  • biota
  • environment
  • inlandWaters

National Agricultural Library Thesaurus terms

bioassays; invasive species; toxicity; 2; 4-D; glyphosate; imazamox; diquat; Megamelus; biological control; Eichhornia crassipes; aquatic weeds; biological control agents; mortality; field experimentation; insects; integrated weed management

OMB Bureau Code

  • 005:18 - Agricultural Research Service

OMB Program Code

  • 005:040 - National Research

ARS National Program Number

  • 304

Pending citation

  • No

Public Access Level

  • Public

Preferred dataset citation

Moran, Patrick J. (2023). Data from: Toxicity of herbicides used for control of waterhyacinth in the California Delta towards the planthopper Megamelus scutellaris released for biological control. Ag Data Commons.