Dallas gardeners perceive mixed impacts of mosquito spraying

Mosquito spray planes line up for takeoff from Dallas Executive Airport last August. 2012 was the first time since 1966 that aerial mosquito spraying was conducted over Dallas county. Photo by WFAA, Monika Diaz.

For us who lived through the summer of 2012 in north Texas, this year might well be remembered as the “Year of the Mosquito”.  A perfect storm of weather and ecological conditions conspired this year to make it the worst year ever for West Nile virus transmission in Texas, and the second-worst year nationwide.  There were more WNV cases this summer in Dallas County (388) than any previous year (the previous worst year was 104 cases in 2006).

On the other hand, for many residents of Dallas and surrounding counties, 2012 may also be remembered as the “Year of Aerial Insecticide Sprays”.  For the first time since 1966, airplanes were used to apply insecticide over the city in an effort to slow the alarming number of human cases of mosquito-borne disease.

Needless to say, there was much public and official concern this summer about the impacts of aerial spraying on both human health and the environment. So when Dallas County Master Naturalists, Sue John and Marilyn Waisanen, approached me in early August looking for ideas for an entomology project, we immediately agreed that a study of the impact of aerial spraying on backyard beneficial insects and fish would be appropriate.

Because of the short time we had to organize the study, we decided to assess the perceptions of gardeners concerning the impact of the sprays on their backyard bees, butterflies, spiders and fish.  We developed an online survey and Sue and Marilyn mined their social networks for willing participants from the gardening and beekeeping communities.  Ultimately we got 75 people to tell us what they thought went on in their gardens while the spray planes buzzed overhead.

The results were interesting and reflected the diverse array of opinions and feelings about mosquito spraying.  Instead of a strong consensus, the gardeners we surveyed were strongly split between seeing little to no adverse effects on backyard wildlife, to seeing strong impacts on their birds and bees.  For each one who said, “I observed no change in insect activity” there was another who reported, “I have noticed [fewer] mosquitoes… butterflies, dragonflies, [and] flies. Have not been able to find any… praying mantis…”

Without actual insect counts, it’s hard to say who was more accurate in reporting the real impact of sprays on the butterflies, bees and spiders.  However respondents who observed fish and bees reported no major problems following spraying.  Of those with fish in ponds, 14 of 17 covered their ponds. Of these, 88% reported no or slight impacts of the sprays on their fish. None of the three gardeners who chose not to cover their ponds reported any fish loss. Of those with bee hives or colonies in their backyards, four (80%) reported no observable impact, and one reported slight impact.  If the study shows anything, it supports the contention of public health officials that there would be no ecological disasters after the spraying.

For those who would like to see the actual results and read more, a copy of the study can be found by clicking here.  Thanks to Sue and Marilyn for their hard work contacting participants, reviewing and validating surveys, and helping write the final report.



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