ARS and collaborating scientists in 10 states are using 20-foot bug vacs to collect critical data on the fate of soybean aphids and other flying insect pests.
Photo by Doris Lagos-Kutz
During the third week of May, Agricultural Research Service scientists Doris Lagos-Kutz and Glen Hartman venture into a nearby field to set a timer on a chimney-like device that rises 20 feet into the air and serves one purpose: winged insects such as aphids (especially soybean aphids), thrips, and other potential soybean pests.
Known as the “suction trap,” the fan-driven device is one of around 30 devices that are buzzing in 10 states as part of a network to collect annual seasonal data on the migratory flight patterns and geographic distribution of the soybean aphid Aphis glycines. Ultimately, such information can help improve the timing and use of countermeasures to mitigate the damage caused by the sap-sucking insect, an invasive species native to Asia that has been a major pest of the 40th since its discovery in 2000. US soybean crop has grown to $ 9 billion.
If insecticides, resistant strains, and biological control equals the weapons of war against the soybean aphid, the traps could be compared to a primary means of gathering valuable information about the pests, noted Lagos-Kutz, a research fellow, and Hartman, a plant pathologist with the ARS- Department of Soybean / Corn Germ Plasma, Pathology and Genetics in Urbana, Illinois.
In this and other conditions, the traps run from 7:00 a.m. to 8:00 p.m. daily from mid-May to mid-October, drawing in air at a rate of 60 cubic meters per second – a force that plucks small insects in the air straight from the sky and guides them in a plastic container filled with a sample-preserving solution of water and antifreeze. A mesh screen over the top of the traps prevents larger winged animals such as bats and birds from facing a similar fate.
After receiving the suction trap samples collected by employees of the research station, Lagos-Kutz and Hartman sort and process the contents of the container once a week in their laboratory. They call the slurry of wings, legs, insect debris and invisible microorganisms that live on or in the unfortunate insects “aerobiological soup”. The term also reflects the wealth of data that can be gleaned from the traps about where insects move, mainly in the summer and fall seasons.
David Voegtlin of the Illinois Natural History Survey originally designed the data collection and analysis in 2001. Known as the Suction Trap Network (STN), its success today is evidence of the collaboration between participants in several states, according to Lagos-Kutz. These include Illinois, Indiana, Iowa, Kansas, Louisiana, Michigan, Minnesota, Missouri, Nebraska, and Wisconsin. Support for the STN over the years has been provided in part through the North Central Soybean Research Program and the ARS “Integrated Management of Soybean Pathogens and Pests” project.
Some of the lessons that emerge from the effort are:
Soybean aphid outbreaks vary by year and location. For example, in the fall of 2009, soybean aphids had been blown up in such large numbers that people in Illinois mistook the flying pests for mosquitos.
An analysis of 9,167 trap samples from 2001 to 2018 found that Illinois, Indiana, Iowa, Michigan, Minnesota, and Wisconsin had the highest numbers of aphids, ranging from 146,114 (Minnesota) to 167,893 (Illinois). Kansas and Kentucky had the lowest scores at 13,509 and 14,329, respectively.
A total of 152 aphid species were identified, excluding captured specimens that scientists have not yet identified. The most commonly identified species, besides soybean aphids, were Rhopalosiphum padi, R. maidis, Pemphigus spp., Tetraneura spp., Therioaphis trifolii, Capitophorus elaeagni, R. rufiabdominale, and Sitobion avenae.
Aphids typically migrate between winter host plants (sea buckthorn), on which the pest survives as eggs during the cold months, and then to soybeans, their summer host plants (spring migration). They also move inside and outside of their summer host plant fields (summer hike) and back to the winter host plant (autumn hike).
Suction trap data also provides valuable information on other insect species, including thrips and mosquitoes. For example, studies of nine species of mosquitoes have found symbiotic bacteria that affect the biology, reproduction and ability of their blood-feeding hosts to transmit parasites and pathogens, and open the door to new ways of combating those that cause disease in humans.
Other uses for suction trap data include tracking pest populations with traits for insecticide resistance, studying the effects of climate or habitat changes on pest populations, and detecting the spread of pests to new areas such as the sugarcane aphid that moved to Kansas, Manhattan. , Missouri (Columbia and Portageville), Louisiana (Chase), and northern Wisconsin.
Details of the project were published in the March 2020 issue of the American Entomologist by Lagos-Kutz, Hartman, Voegtlin and their co-authors.
Extending the suction traps to new states could also help paint a broader picture of the “aerial microbiome,” the community of microbes that reside within flying insects in transit. Similar studies are currently being carried out for microbiomes in soil, water, and even in the human body, Hartman said.
