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Weeds and WeedMapper

  • Are noxious weeds considered noxious or invasive in their host countries?For the most part, no. These plants have existed for centuries in their host county, but their populations have been kept to manageable levels naturally by other plant competition, insects, pathogens and a host of other predators. When plant populations in these countries of origin increase, insects and other predators increase accordingly to help keep them in check.
  • Has there been a resurgence of tansy ragwort in the Willamette Valley?Tansy maintained a low profile until 2005, when a winter drought was followed by a warm wet spring, which created the conditions for its resurgence. Because tansy populations were low, so were the biocontrol agent populations that depend on the weed. This is a natural cycle and it will take several years for the insects to build up and re-control tansy. Tansy has made a big comeback in parts of the Willamette Valley, especially in the foothills, where livestock grazing is prevalent. Most major infestations are enclosed by a fence, which indicates that something is wrong with the whole plant community. Inspection at those sites indicated that disturbance from rodents such as field mice and gophers, were creating microsites where the weed could flourish. The conditions of a long wet spring are great for tansy, but not so great for the insects, and tansy has retaken a strong hold at some sites.
  • How can I apply for a Noxious Weed Control Program grant?The Noxious Weed Control Program administers and provides technical expertise to the Oregon State Weed Board Grant Program. Landowners or managers fighting noxious weeds will want to check our grant program website.
  • How can I get my neighbors to control their weeds?Try talking to your neighbors first to explain the importance of controlling weeds. Depending on where you live, there may be local programs that mandate the control of noxious weeds on private property. Homeowner associations can direct weed control to their members. Some local government entities have codes or regulations that mandate weed control. Noxious Weed Control Districts or Weed Management Areas can help your neighbors control their weeds by education and outreach, land management strategies, and/or funding. Weed control is everybody’s business.
  • How did noxious weeds get here and where did they come from?Most of Oregon’s least desirable weeds are of Mediterranean, European, and Asian origin. The introduction of non-native invasive plants has increased dramatically in the past decade because of the increased ease and speed of world travel and the expansion of global commerce. Local spread of noxious weeds can be natural by wind, water, and animals; but human activities such as, recreation, vehicle travel, and the movement of contaminated equipment, products, and livestock often greatly increase the distance and rate of dispersal.
  • How do I find out whether a plant I am selling is a noxious weed?Review the Noxious Weed Control Program’s state noxious weed list and program site. Noxious weed lists for other states can be found on the National Plant Board Laws and Regulations website.
  • Is butterfly bush a listed noxious weed?If you planted your butterfly bush before it was listed (2004), you do not have remove it, but you are required to prevent it from propagating. You must deadhead the plant after blooming to prevent the seeds from spreading. Better yet, replace your butterfly bush with some native or non-invasive plants. Your local nurseries can help you choose a range of shrubs to replace your butterfly bush.
  • What is a noxious weed?A weed is designated noxious when it is considered by a governmental agency to be injurious to public health, agriculture, recreation, wildlife, or property (Oregon Administrative Law 603-052-1200). Most noxious weeds are non-native plants that are serious pests causing economic loss and harm the environment. Noxious weeds choke out crops, destroy range and pasture lands, clog waterways, affect human and animal health, and threaten native plant communities.
  • What is an NPDES permit and do I need it?The Oregon Department of Environmental Quality (DEQ) has a Clean Water Act permit requirement for certain pesticide applications, in, over, or near waters of the state. A National Pollutant Discharge Elimination System (NPDES) pesticide general permit is required by a federal court order and is implemented in Oregon by the DEQ under an agreement with the EPA.
  • Where can I find the weed distribution in the state?Weedmapper is a tool that allows you to access noxious weed distributions in the state. Follow the simple user guide see weed profiles and locations.
  • Whom do I call with noxious weed control questions?Local ODA Noxious Weed Control staff are experts in integrated weed management and are familiar to the counties and areas in which they serve. Additionally, there are other agencies or groups in Oregon that can help with your weed control questions. Be an active participant in preserving Oregon's natural resources by knowing the invasive plant fighters in your area.


Noxious Weed Control
635 Capitol St. NE
Salem, OR 97301
Phone: 503-986-4621
Fax: 503-986-4786