Non-Target Studies: Bti (Bacillus thuringiensis var. israelensis) and Methoprene in Wetlands
Scientific Peer Review Panel
In response to concerns about possible effects of mosquito control on other organisms, MMCD assembled an independent Scientific Peer Review Panel (SPRP) in 1985.
The Panel was charged to develop a research program to gain better understanding of ecological consequences of larvicides. They worked for 10 years and designed studies, hired contractors, directed funding (provided by MMCD), and reviewed results.
SPRP Activity Chronology and Origin
Their Final Report includes literature review, results of lab and field studies on direct and chronic effects, and discussion of implications.
SPRP Final Report, 1996 [PDF – 5Mb, 66 pp.]
- Literature review and laboratory studies on direct and chronic effects
- Field studies of historically treated sites or divided sites
- Field studies of wetland birds in treated or untreated sites
- Long-term field study of birds, invertebrates and zooplankton (Wright Co.)
Wright County Long-term Non-target Impact Study
The largest project developed by the Panel, this study was conducted on 27 previously untreated wetlands in Wright Co., Minnesota. Sites were studied 3 years before treatment, assigned to Bti, methoprene sand, or untreated control, and treated 6 times per year for 9 years (1991 – 1999).
Long-term study brief overview
No difference due to treatment was found for zooplankton, breeding Red-winged Blackbirds, or the bird community in the wetlands in 3 years of treatment.
Hanowski1997a Abstract
Hanowski1997b Abstract
Macroinvertebrates in sediment core samples showed no difference in 1991. Later sampling dates from 1992 and especially 1993 showed significant decreases in insects, mostly Chironomidae (non-biting midges). In 1997-98 after 7 and 8 years of treatment, invertebrate numbers were high in all sites and there was no treatment difference in total Chironomid numbers or biomass. On some dates, some groups within the Chironomidae were measurably higher or lower in abundance in treated sites. (No sampling was done in 1994-1996)
8 year results: Balcer et al. 1999
Differences between years may have been related to doses applied, timing, or other factors such as vegetation development and population recovery following dryness.
A study of frog malformation rates done at these sites for 2 years found no detectible difference related to treatment (Johnson et al. 1999 [PDF – 1Mb], also see Summary in Results Summary Presentation [PDF – 2Mb] ).
The“Results Summary” was presented to the Entomological Society of America (1999), American Mosquito Control Association (2000), Society of Wetland Scientists (2001), and Mid-Atlantic Mosquito Control Association (2002).
Work is continuing on publishing the 8 year invertebrate results.
If you need further assistance, contact Dr. N. Read, Technical Services, MMCD, email: nancread@mmcd.org
Last updated Aug. 10, 2005