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United States Department of Agriculture

Agricultural Research Service

Title: Leafy Spurge – Unwelcome Pest to a Modern Day Model Plant

Author
item Anderson, James

Submitted to: Leafy Spurge News
Publication Type: Trade Journal
Publication Acceptance Date: September 20, 2005
Publication Date: October 1, 2005
Citation: Anderson, J.V. 2005. LEAFY SPURGE – Unwelcome Pest to a Modern Day Model Plant. Leafy Spurge News. Volume XXVII(1):8.

Interpretive Summary: Leafy spurge has been known since at least 1000 AD when Eurasian communities designated it as wolf’s milk. Unfortunately, as ship yards, the rail system, and immigrants unintentionally introduced leafy spurge seeds into North America, the natural control mechanisms indigenous to Eurasia were not also introduced. Since its introduction and spread into the mid-western states in the late 1800’s we have burned, cultivated, grazed, infected, mowed, pulled, sprayed, extensively studied, and yes, even cursed it, and yet we can’t get rid of it. Heck, leafy spurge has gained such attention in the Northern Plains that we have even named festivals after it. However, starting in the 1990’s, the introduction of natural enemies, such as flee beetles, provided a promising new addition to an already extensive integrated pest management (IPM) approach. In fact, the control of leafy spurge by natural enemies is a success story in areas where it has reduced the stand density or kept in check its spread. Unfortunately, natural enemies are not successful in all ecosystems and research to develop additional IPM measures for this resilient pest is required. So, what is it that makes this plant so resilient to every thing in the kitchen sink and more? Vegetative reproduction from an abundance of underground adventitious crown and root buds and dormancy within these vegetative buds, and seeds, are the main mechanisms for persistence of this weed. Like most perennial plants, leafy spurge is capable of growing new shoots from vegetative propagules when the above ground tissues are damaged, killed, or removed. However, very few chemical applications are either practical or effective at killing crown and root buds of leafy spurge. Dormancy within these reproductive organs optimizes the distribution of shoot emergence over time, and therefore is one of the leading factors that allow many weeds to escape current control measures. Current IPM recommendations are essentially designed to reduce the energy carrying reserves in the root system over time, which ultimately reduces its capacity to compete and survive within the ecosystem. However, leafy spurge seeds also are capable of remaining dormant within the soil seed bank for up to 8 years and reestablishment of seemingly eradicated patches is common. Just as you and I adapt to our environment, so do weeds like leafy spurge. Survival depends on it! Interestingly, it is the same weedy characteristics that make leafy spurge such a nuisance in rangeland and other ecosystems that actually make this plant a potential model for advancing our understanding of dormancy, not only in weedy perennials, but for economically important perennial crop plants as well. In the November/December 2005 issue of the journal Weed Science, Research Scientists in our unit published a paper entitled “Potential model weeds to study genomics, ecology, and physiology in the 21st century.” In this article, we make compelling arguments for promoting leafy spurge as a model plant for the study of perennial broadleaf weed species (Canada thistle, field bindweed, etc.) based on its known weedy characteristics, ease of propagation, existing tools, stakeholder support, a scientific community, and funding. Although weedy plants will likely never gain the attention and support lavished on most crop plants, knowledge gained from the study of dormancy in a model perennial such as leafy spurge could be used to enhance production of perennial crops such as alfalfa, berries, grapes, and fruit and poplar trees that have an economic impact on global agriculture. The greatest potential for enhancing our understanding of bud dormancy and vegetative reproduction, and hence discovering new management strategies, is dependent on our unique genomics-based research program for studying global patterns of gene expression in the model noxious perennial weed, l

Technical Abstract: Leafy spurge has been known since at least 1000 AD when Eurasian communities designated it as wolf’s milk. Unfortunately, as ship yards, the rail system, and immigrants unintentionally introduced leafy spurge seeds into North America, the natural control mechanisms indigenous to Eurasia were not also introduced. Since its introduction and spread into the mid-western states in the late 1800’s we have burned, cultivated, grazed, infected, mowed, pulled, sprayed, extensively studied, and yes, even cursed it, and yet we can’t get rid of it. Heck, leafy spurge has gained such attention in the Northern Plains that we have even named festivals after it. However, starting in the 1990’s, the introduction of natural enemies, such as flee beetles, provided a promising new addition to an already extensive integrated pest management (IPM) approach. In fact, the control of leafy spurge by natural enemies is a success story in areas where it has reduced the stand density or kept in check its spread. Unfortunately, natural enemies are not successful in all ecosystems and research to develop additional IPM measures for this resilient pest is required. So, what is it that makes this plant so resilient to every thing in the kitchen sink and more? Vegetative reproduction from an abundance of underground adventitious crown and root buds and dormancy within these vegetative buds, and seeds, are the main mechanisms for persistence of this weed. Like most perennial plants, leafy spurge is capable of growing new shoots from vegetative propagules when the above ground tissues are damaged, killed, or removed. However, very few chemical applications are either practical or effective at killing crown and root buds of leafy spurge. Dormancy within these reproductive organs optimizes the distribution of shoot emergence over time, and therefore is one of the leading factors that allow many weeds to escape current control measures. Current IPM recommendations are essentially designed to reduce the energy carrying reserves in the root system over time, which ultimately reduces its capacity to compete and survive within the ecosystem. However, leafy spurge seeds also are capable of remaining dormant within the soil seed bank for up to 8 years and reestablishment of seemingly eradicated patches is common. Just as you and I adapt to our environment, so do weeds like leafy spurge. Survival depends on it! Interestingly, it is the same weedy characteristics that make leafy spurge such a nuisance in rangeland and other ecosystems that actually make this plant a potential model for advancing our understanding of dormancy, not only in weedy perennials, but for economically important perennial crop plants as well. In the November/December 2005 issue of the journal Weed Science, Research Scientists in our unit published a paper entitled “Potential model weeds to study genomics, ecology, and physiology in the 21st century.” In this article, we make compelling arguments for promoting leafy spurge as a model plant for the study of perennial broadleaf weed species (Canada thistle, field bindweed, etc.) based on its known weedy characteristics, ease of propagation, existing tools, stakeholder support, a scientific community, and funding. Although weedy plants will likely never gain the attention and support lavished on most crop plants, knowledge gained from the study of dormancy in a model perennial such as leafy spurge could be used to enhance production of perennial crops such as alfalfa, berries, grapes, and fruit and poplar trees that have an economic impact on global agriculture. The greatest potential for enhancing our understanding of bud dormancy and vegetative reproduction, and hence discovering new management strategies, is dependent on our unique genomics-based research program for studying global patterns of gene expression in the model noxious perennial weed, leafy spurge. Important components of genomics-based programs are Expressed Sequence Tag (EST)-databases which can be used to identify unique gene sequences for the construction of DNA microarrays. Microarray technologies are now standard procedures in modern biotechnology laboratories which allow scientists to study the global expression of hundreds to thousands of genes in one experiment. Through various in-house, collaborative, and competitively funded programs, we now have in excess of 50,000 ESTs in our leafy spurge database. These ESTs represent in excess of 23,000 unique sequences which are currently in the process of being organized for the construction of DNA microarrays. We already have plans to use the leafy spurge microarrays to identify the signaling pathways involved in regulating dormancy in crown and root buds. Understanding how these signaling pathways regulate dormancy will enhance our understanding of potential treatments to manipulate dormancy and vegetative reproduction. This new information will be an important addition to the current IPM strategies. So the next time you are standing on that butte that overlooks the pasture infested with leafy spurge, go ahead and kick the dirt and curse the scourge. But remember, behind the scenes fundamental research is quietly being done with this model plant to provide important clues to dormancy and the control of perennial weeds.

Last Modified: 7/22/2014
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