Location: Invasive Plant Research LaboratoryTitle: Release and establishment of Megamelus scutellaris (Hemiptera: Delphacidae) in Florida) Author
Submitted to: Florida Entomologist
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/9/2014
Publication Date: 6/1/2014
Citation: Tipping, P.W., Sosa, A., Pokorny, E.N., Foley, J.R., Schmitz, D.C. 2014. Release and establishment of Megamelus scutellaris (Hemiptera: Delphacidae) in Florida. Florida Entomologist. 97:804-806.2014. Interpretive Summary: More than 73,000 adults, nymphs, and eggs of the biological control agent Megamelus scutellaris were released in Florida over a two to three year period at 10 sites in an attempt to establish sustainable populations on waterhyacinth, Eichhornia crassipes. Insect populations persisted at most sites including those furthest north and consecutive overwintering was confirmed in as many as three times at some sites. Establishment appeared to be promoted at sites with some cover or shading compared to open areas. Insects readily dispersed over short distances which made detection and monitoring difficult. Cages helped to hold the insects in one place to concentrate oviposition and aid in monitoring. The weight of evidence indicates that his species is now established on waterhyacinth in Florida.
Technical Abstract: Megamelus scutellaris (Berg) (Hemiptera: Delphacidae) was recently developed as a classical biological control agent for waterhyacinth, Eichhornia crassipes Mart. Solms, and released in Florida. Releases were conducted at 10 sites around the state every 4-6 weeks until late fall then halted until the following spring to determine if overwintering had occurred. No new releases were made at sites after overwintering was confirmed except in cases where the sites were reconstituted because of perturbations like flooding or drought. Releases in South Florida were done opportunistically with no attempts to assess overwintering because the climate permitted plant and insect development throughout the year. Insects or infested plants were placed directly on or within existing mats of E. crassipes, in floating cages (1 m3) located atop pvc frames, in above ground tanks, or in portions of uncaged mats within floating pvc frames that enclosed 1 m2 and were surrounded by open water. Smaller, lighter ('throw') cages (0.25 m3) that rested solely atop mats were also used and relocated with each new release. Plants in floating frames or cages were searched for 5 minutes and the numbers of large and small nymphs and adults were recorded. The coldest site for releases in Florida was in Gainesville located in outdoor tanks where M. scutellaris, despite several below-freezing nights a year, overwintered for three straight years. The best side-by-side comparison of environmental influences on M. scutellaris establishment was the St. Johns marsh sites (floating pvc frames) where no overwintering was recorded at the more open St. Johns marsh #1 site, while two consecutive years of overwintering was documented in the nearby and more covered St. Johns marsh #2 site which had overhanging trees. Megamelus scutellaris readily disperses through a mat of E. crassipes as evidenced by the difficulty in finding adults even within a few days of release. Although larger cages sealed atop frames largely prevented emigration, moats and throw cages appeared to only delay it. Predators of nymphs and adults included fish and spiders, along with occasional egg parasitism by unidentified Mymarids and nymph and adult parasitism by an unidentified Dryinid.