Fire Ants May Offer Insight Into Crippling Honey Bee Disease
By: Jessica Ryan
Email: arspress@usda.gov
Agricultural Research Service (ARS) scientists are helping to protect honey bee populations while developing new strategies for managing fire ant populations. Honey bees are a vital part of pollinating our crops, while fire ants – an invasive species -- pose a major threat to humans, animals, and U.S. agriculture.
ARS scientists are getting a better understanding of Deformed Wing Virus (DWV), a major pathogen that can debilitate honey bees and adversely affect entire colonies. They found that the virus also affects fire ants, which could aid in spreading the virus to other species, including bees.
In the United States, imported fire ants have infested more than 367 million acres. These pesky insects can cause over $6 billion in annual losses as they feed on important crops, displace native ant species, and reduce wildlife food sources.
A side-by-side comparison of red imported fire ants with no wing deformities and red imported fire ants with wing deformities. (Photos by Godfrey P. Miles, ARS)
DWV is a serious disease that is transmitted by Varroa mites and affects different insects. In honey bees, the virus causes wing deformities, shortened abdomens, discoloration, and neurological or mobility impairments. The presence of DWV can result in reduced bee populations and colony decline.
A team of researchers from ARS and Mississippi State University’s Delta Research and Extension Center have detected DWV in red and black imported fire ant colonies in Mississippi. In one study, scientists observed that infected red imported fire ants and honey bees exhibited similar symptoms after contracting DWV. A separate study published similar findings for black imported fire ants.
Red imported fire ant specimens displaying deformed wing (DW) phenotype. (A) Normal winged (NW) adult male ant with wings (also known as alates). (B and C) two DW male alates from different colonies. (D) Two melanized male pupae with DW (bottom) and NW (top). Scale bars are set at 1 mm for all images except image C, which is 0.5 mm. (Photos by Godfrey P. Miles, ARS)
“We determined that the virus is replicating in both black and red imported fire ants, which means these fire ants could potentially serve as hosts for DWV,” said Jian Chen, a research entomologist at the ARS Biological Control of Pests Research Unit in Stoneville, Miss.
“We also observed symptoms of deformed wings and impaired mobility in some infected laboratory and field colonies of both red and black imported fire ants, like those found in infected honey bees. However, whether DWV is causing these symptoms has not yet been determined.”
These findings may be alarming for beekeepers who want to protect their bee colonies. Chen emphasized that this information could help researchers understand how the virus affects different insect species and find ways to control the virus.
Red imported fire ant specimens displaying deformed wing (DW) phenotype. (A) Normal winged (NW) adult female ant with wings (also known as alates). Image (B) DW female alate with moderate level of wing deformity. Image (C) is a female DW alate with severe wing deformity and (D), is this same female alate under higher magnification. Scale bars are set at 1 mm for all images except image D, which is 0.5 mm. (Photos by Godfrey P. Miles, ARS)
“Further research will be needed to explore how DWV impacts fire ant populations and how the virus is transmitted between different species,” Chen said.
“Fire ants and bees often interact in nature, as they share food sources such as honeydew and nectar. Additionally, virus-infected bees may serve as a protein source for ants. While we do not yet know if ants can transmit the virus to bees, fire ants are very common in bee yards in areas where they are established.”
ARS scientists and collaborators have sequenced the genomes of DWV variants. DWV is an RNA virus with several variants, including variant A (the original strain spread worldwide through varroa mites) and variant B (the current increasing strain globally). Researchers have successfully sequenced the DWV genome of variant A (DWV-A) and variant B (DWV-B) in red imported fire ants.
The Agricultural Research Service is the U.S. Department of Agriculture's chief scientific in-house research agency. Daily, ARS focuses on solutions to agricultural problems affecting America. Each dollar invested in U.S. agricultural research results in $20 of economic impact.
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