Pacific Nut Producer Magazine

Tag: Agricultural Research Service

  • Varroa Mites and Deformed Wing Virus Make Honeybees More Susceptible to Insecticides

    The first of two apiaries, established in 2014 in Stoneville, Mississippi, provided honey bees for studying the impact of pesticides on honey bees. (Photo by Yu-Cheng Zhu, D5121-1)

    Controlling for Varroa mites, the parasitic mites that feed on honey bees and serve as vectors for viral diseases like deformed wing virus (DWV), can help with improving honeybee populations and make bees less susceptible to harmful insecticides, according to a recent study published in Environmental Pollution.

    Foraging honey bees may be directly exposed to toxic insecticide sprays in the field or exposure may come from honeybees collecting and bringing pesticide-contaminated pollen and nectar back to their hives to feed larvae and young bees. The presence of insecticides, along with other environmental stressors in agricultural areas, can be a factor leading to issues like colony loss — something beekeepers from around the world are trying to overcome.

    “Previous research has shown how chemicals like pesticides make bees more susceptible to mites,” said Yu-Cheng Zhu, a research entomologist at ARS’s Pollinator Health in Southern Crop Ecosystems Research Unit in Stoneville, Mississippi. “In our study, we wanted to see if mites and viral infestations make bees more susceptible to insecticides.”

    In a study, researchers with the U.S. Department of Agriculture (USDA)’s Agricultural Research Service (ARS) applied the miticide amitraz (Apivar), a product commonly used for treating Varroa mites, off-label to four bee hives and left the other four hives untreated. They monitored the mite population density monthly and DWV density in early, middle, and late season.

    Researchers collected bees from miticide-treated and untreated hives, and quantified gene expressions of four immune genes and two physiology-related genes. They also tested bees’ sensitivity to five representative insecticides. In addition, bees’ natural mortalities were recorded during three seasons.

    “Miticide treatment led to minor or undetectable mite and DWV infestations during the whole bee season, while untreated colonies had substantially higher mite and DWV infestations,” said Zhu.

    The data analyses showed that Varroa mite population irregularly fluctuated over the bee season and mite population density was not dynamically or closely correlated with the seasonal shift of honey bee natural mortality. Unlike mites, DWV density in untreated colonies progressively increased over the bee season. The density was highly correlated with the seasonal increase in honey bee natural mortality.

    “In the untreated hives, the increased DWV infestations resulted in decreased physiological and immunity-related functions in late-season honey bees, making the bees more susceptible to insecticides and increasing natural morality rates during the season,” said Zhu.

    According to Zhu, Varroa mites, also known as Varroa destructor, can reduce fat body and body fluids that contain important detoxification enzymes and immune proteins in honey bees. As a result, bees have impaired immune, detoxification/defense systems, and other essential processes. Coupling those impairments with exposure to insecticides can be detrimental to bee populations.

    “Having impaired immunity, especially later in the season with fewer food sources, can be challenging for honey bees,” said Zhu.

    Zhu, whose work focuses on the toxicological impact of pesticides on beneficial insects in the Mississippi Delta Area, said that the study’s results indicated the importance of studying the “bottom-up” effects of mite infestations on the overall health of honey bees in real-world contexts.

    “Chemical control is still a major method in preventing crop loss and controlling insect pest populations,” said Zhu. “It is important to study the effects of chemical control in honey bee populations so we can find best practices for protecting the health of bees.”

    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.

  • Protecting Pecans with Friendly Fungi

    On July 1, 1930, the Agricultural Research Service (ARS) formally began its pecan research and breeding program in Austin, TX. With this support from ARS scientists, the United States became the world’s leading producer of pecans, a crop estimated to be worth over $560 million.

    Nearly a century later at the ARS Fruit and Tree Nut Research Station in Byron, GA , team members David Shapiro-Ilan, Fernando Vega, Tshima Ramakuwela (visiting Borlaug Fellow), and collaborators from Fort Valley State University and University of Georgia continue to build upon this legacy by developing newer and smarter ways to protect this beloved crop.

    According to their research, fungi that can naturally disable or eliminate insects may be key to protecting pecans’ future. Shapiro and his team identified two particularly “friendly fungi,” Beauveria bassiana and Metarhizium brunneum.

    Although harmless to humans, both fungi have shown an ability to effectively control economically damaging insects like pecan weevils, aphids, and stink bugs. There also appears to be a positive correlation between the presence of those fungi and the growth of the plants they’re applied to, leading to increased plant height, number of leaves, and root length.

    “For growers and consumers interested in organically grown pecans, this is an exciting finding,” said Shapiro. “More than ever, conventional pesticides are discouraged because of the chemical residues they leave behind that can hurt not only nontarget organisms, but also the overall environment. Fungi like B. bassiana, on the other hand, are naturally occurring, relatively widespread, and safe for people and plants. This is a big step in ensuring the productivity, profitability, and environmental sustainability of U.S. pecan production.”

    In conventional agriculture, crops are typically sprayed with chemically formulated pesticides. Insect-killing fungi such as B. bassiana and M. brunneum can also be sprayed using most standard agricultural equipment. However, fungi like B. bassiana are also endophytes – meaning they can live within the tissues of a host plant. Because of this characteristic, B. bassiana can coexist with and offer protection to pecan plants at the earliest stages of growth. The fungus is applied via a relatively simple inoculation process.

    There are several different approaches that even home gardeners or noncommercial pecan tree growers can replicate, said Shapiro. For example, a pecan seed can be rolled in fungus-spore powder or soaked in a fungus-spore solution. If the pecan plant has already sprouted into a seedling, drenching the soil around it with a high concentration of the fungus or spraying the leaves with the spores will also inoculate the crop. The protection provided by the inoculation can last as long as 3 years, which may be critical to ensuring the plants reach pecan-producing maturity.

    Beyond their potential as biopesticides and organic growth promoters for pecans, B. bassiana and M. brunneum have also successfully defended plants and people from threats like fungal diseases and pests such as mites, bedbugs, and mosquitoes. ARS continues to investigate the additional benefits of endophytes to pecan trees and other crops. – By Georgia Jiang, USDA-ARS Office of Communications

  • First Genome of Spotted Lanternfly Built from a Single Insect

    Agricultural Research Service (ARS) scientists, in cooperation with Pacific Biosciences and Penn State University, have published the first genome of the invasive Spotted Lanternfly (SLF) in the journal Gigascience and they did it from a single caught-in-the-wild specimen.

    Not only is it the first published genome for this pest, but no closely related species has had its genome sequenced, making the data even more important, according to entomologist Scott M. Geib with the ARS Daniel K Inouye U.S. Pacific Basin Agricultural Research Center.

    SLF, a native of China, Bangladesh and Vietnam, was first found in Pennsylvania in 2014 and has now spread to Virginia, Maryland and New York. This invasive pest has a taste for almonds, apples, apricots, grapes, peaches, blueberries and hops as well as hardwoods such as oak, walnut, and poplar. Various estimates put the potential economic damage in the billions of dollars, if the SLF becomes widely established in the United States.

    “Having the genome for this pest opens the door to a better understanding of its biology and behavior, and makes coming up with potential control methods much more likely to happen, such as developing a lure for a trap through understanding the insect’s olfactory genes, or exploring avenues such as gene editing or RNAi,” said Geib.

    While having the SLF genome is critical for the management and control of this invasive pest, the approach taken to obtain the genetic data is an achievement of remarkable note as well. For the first time, all of the DNA required to generate a whole genome sequence was taken from a single insect picked from a tree in the wild in Reading, Pennsylvania, across the street from the Reading Pagoda on Mt. Penn.

    One hurdle for deciphering this species’ genome is its relatively large genome size, at about 2.2 billion base pairs. Typically, with previous sequencing systems, many sequencing runs would have been needed to do the complete job, with each run using up the available DNA for the organism being sequenced.

    So often to have sufficient DNA for a complete genome sequence, many organisms would need to be pooled, introducing more opportunities for errors to be generated. To avoid such potential for errors, the subjects—especially insects—often have to be raised in colonies and inbred.

    “In cooperation with Pacific Biosciences and using their new sequencing platform—the PacBio Sequel II—that produces 10 times the data from a single sequencing run, we were able to generate sufficient coverage from just a single specimen. This allows for a very fast turn-around of data and assemblies as well as lowers cost, in this case under $2,000 in consumable supplies, not including the purchase price of the sequencing instrument of course,” explained Geib.

    For genome completeness, and since there aren’t many related genomes to compare that of the SLF to, the team checked a set of “core genes” that should be present exactly one time in all insects and verified how many of these were found in this genome project. In this case, they found about 97 percent of these single copy core genes, with a very low rate of duplication.

    “Sequencing such a large insect genome quickly and showing there is no need to pull the insect into a colony raises the feasibility that we can complete the Ag100Pest Project,” Geib said. The ARS Ag100Pest initiative is focused on deciphering the genomes of 100 insect species that are most destructive to crops and livestock and that are projected to have profound bioeconomic impacts to agriculture and the environment. “Now, with this system, doing 100 or even 1,000 genomes is not unrealistic,” he added.

    The ability to get a complete genome from a small amount of DNA also makes it practical to consider sequencing the genomes of physically tiny insects without having to catch or raise a large number of any one species. That expands the list of insects that may be genetically sequenced.

    By Kim Kaplan, USDA-ARS

    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 agricultural research results in $20 of economic impact.