After 13 Years and 1.7 Million Flies Caught, a Model for Predicting Stable Fly Populations
Think for a moment about the date May 15, 2003. Any idea what you were doing that day? (It was a Thursday.) And can you think of anything that you’ve done a couple times a week, every week, in the nearly 14 years since?
David Taylor, Ph.D., and a team of colleagues and students have been catching flies.
To be exact, they caught 1,769,405 of them—stable flies (Stomoxys calcitrans)—between May 15, 2003, and December 31, 2015. It was all part of an ongoing, long-term study conducted at the University of Nebraska-Lincoln by the U.S. Department of Agriculture’s Agricultural Research Service (USDA-ARS). The results, published last week in Environmental Entomology, offer the most precise model yet for the effects of temperature and precipitation on populations of stable flies, a significant pest of livestock worldwide.
“Stable fly populations fluctuate tremendously not only seasonally but also from year to year. An important component of any integrated pest management program is to know the current trend in the population. As a pest population approaches the economic injury level, one would like to know if the population is going to continue to increase, meriting control measures, or if the population is approaching its peak and will naturally decline in the near future,” says Taylor, research entomologist at the USDA-ARS Agroecosystem Management Research unit.
“In this study, we show that stable fly populations are responding to temperature and precipitation and their dynamics can be predicted using those variables,” Taylor continues. “This information permits more efficient use of control technologies. Negating the need for control using chemical agents when a population is at the cusp of a decline, for instance, reduces selection for insecticide resistance on that population and will slow the development of overall resistance.”
The research team set up 25 fly traps on the 10,000-acre University of Nebraska Agricultural Research and Development Center and checked them twice per week during fly season (May through October) and every two to three weeks during the rest of the year. Meanwhile, weather data was recorded via nearby stations of the High Plains Regional Climate Center. With that mass of collected data, Taylor and colleagues used statistical analysis to arrive at a predictive model based on temperature and precipitation that they say accounts for 70 percent of the variability in stable fly population throughout the year.
“Stable flies are notorious among those working on them for having a mind of their own. They are a tremendously adaptable species, capable of developing in many different types of substrates and adapting to cultural practices around the globe. This makes finding patterns in their behavior quite difficult. That we were able to explain 70 percent of the variation in their population dynamics using only two weather parameters was quite surprising,” Taylor says.
It will be highly valuable information for pest management professionals who work in livestock settings, but, due to the effects of weather variability, arriving at these results was only possible through a long-term study.
“Several factors contributed to being able to conduct such long-term research,” says Taylor. “First, the location where we did the research, the Agricultural Research and Development Center of the University of Nebraska is a large piece of land dedicated to research. Secondly, the USDA Agricultural Research Service is especially amendable to long-term research. Stable funding and long-term perspectives are required for this type of work. Our laboratory is uniquely situated, being a USDA-ARS group located at the University of Nebraska, to address long-term research on a landscape scale. Being located on the campus of the University of Nebraska has also allowed us to hire many excellent students to support our work. Without the students, a project like this would not be possible. Over the years, 20 or more students and several technicians have supported this work.”