Controlling insect pests to protect plant, animal, and human health
ARS collaborates across the human, animal, and environmental health communities to achieve sustained health outcomes for plants, animals, and people. Research at ARS informs and provides solutions to improve the U.S. biodefense posture and encompasses animal health; medical, veterinary, and urban entomology; plant health; and natural resources and sustainable agricultural systems. The following FY 2020 accomplishments illustrate ARS efforts to eliminate arthropod vectors and nullify their impacts.
New and quick method to identify fever ticks resistant to pyrethroids. Cattle fever ticks were eradicated from the southeastern United States but continue to re-infest parts of southern Texas. The presence of wildlife complicates eradication efforts by spreading ticks across the Mexico-United States border into Texas. Pyrethroids are a class of pesticide used to control tick infestations on cattle in Mexico and on U.S. wildlife. However, many tick populations in Mexico are resistant to pyrethroids. Quick and accurate diagnosis of pyrethroid resistance in the cattle fever tick is critical for selecting the appropriate pesticide to use. ARS scientists in Kerrville and Edinburg, TX, and Pullman, WA, worked with collaborators at Northern Arizona University and the University of Queretaro (Mexico) to develop a new and quick method to identify fever ticks resistant to pyrethroids. This assay can detect multiple changes in the gene coding for the protein targeted by pyrethroids and which can lead to resistance. This molecular assay can be completed overnight while the traditional bioassay method takes 6 weeks to complete. The ability to quickly detect pyrethroid-resistant ticks allows decision makers to choose the proper pesticide to use on wildlife during Texas outbreaks.
Ag100Pest project opens new opportunities for invasive pest control. The Ag100Pest Initiative, led by ARS, develops high quality reference genome assemblies for the top 100 U.S. arthropod agricultural pests. These genomic resources are critical for the development of biobased tools for biosecurity. In FY 2020, the Ag100Pest Initiative sequenced the complete genome of the Asian giant hornet, a deadly predator of honeybees first spotted in North America in 2020. The initiative has also sequenced the first genome of spotted lanternfly, an invasive pest of hardwoods and several specialty crops.
Effect of environmental temperature on the ability of mosquitoes to transmit Rift Valley fever virus. ARS researchers in Manhattan, KS, and collaborators at the U.S. Army Medical Research Institute for Infectious Diseases evaluated how environmental temperature affects the ability of two mosquito species native to the United States to transmit Rift Valley fever virus (RVFV). Mosquito incubation temperatures ranging from 14˚C to 26˚C were evaluated for their effect on virus infection, dissemination, and transmission rates. For both mosquito species tested, increased temperature was associated with more rapid and more efficient infections and increased the potential for mosquitoes to transmit RVFV. Although environmental temperature affected the ability of RVFV to replicate and amplify in mosquitoes, the effect differed between the two species. The results indicated that effect of temperature on RVFV dissemination and transmission was species dependent. These data on the effects of ambient temperature facilitate development of more accurate models to assess RVFV persistence and spread in nature should a disease outbreak ever occur in the United States. (NP103, C1, PS1b, Project No. 3020-32000-009-00D)
Treated military uniform compromised by pesticide-resistant mosquitoes. Military camouflage uniforms are routinely treated with permethrin to repel disease-carrying mosquitoes. This preserves an effective fighting force while military members operate in environments where mosquito-vectored diseases are endemic. ARS researchers in Gainesville, FL, and U.S. Department of Defense collaborating scientists completed and published a study clearly demonstrating that treated military uniform efficacy may be completely compromised by pyrethroid-resistant strains of Aedes aegypti, a vector of numerous human diseases. Fortunately, this study also showed that the protection provided by N,N-Diethyl-meta-toluamide (DEET)-based repellents was unaffected by resistance to pyrethroids. This information will aid in the risk assessment of different operational environments and lead to changes in procedures and chemicals used to protect at-risk military members operating in areas where pyrethoid-resistant mosquitoes exist. (NP104, C2, PS2A, Project No. 6036-32000-052-00D)