Working together to strengthen and support noxious weed management efforts in Montana.

Hoary Cress

MSU Report for the Montana Noxious Weed Trust Fund Advisory Council

Wednesday, June 19th, 2013


This report for the Montana Noxious Weed Management Advisory Council was assembled in compliance with the Montana Noxious Weed Trust Fund Act and Administrative Rules which require an annual report from the Montana Agricultural Experiment Station and Montana State University Extension Service on current projects and future plans. This report is a compilation of major weed science research and education activities conducted by MSU over the past three years and includes highlights of funded Montana Noxious Weed Trust Fund grants as well as comprehensive reporting of all weed science research products and education funding and activities.

Montana Noxious Weed Trust Fund Projects 2010–2012

  • Biological Control of Common Tansy and Oxeye Daisy, Jeff Littlefield
  • Biological Control of Invasive Hawkweed and Tansy Ragwort, Jeff Littlefield
  • Biological Control of Russian Knapweed, Jeff Littlefield
  • Biological Control of Whitetop and Perennial Pepperweed,Jeff Littlefield
  • Can Biological Control and Targeted Sheep Grazing be Integrated to Suppress Spotted Knapweed?, Jeff Mosley
  • Cheatgrass Ecology and Integrated Management, Jane Mangold
  • Continental Divide Invasive Weed Barrier Zone, Kim Goodwin
  • Establishing and Monitoring Insectaries for Yellow Toadflax Biocontrol, David Weaver
  • Herbicide Resistance Extension Information for Montana Producers, William Dyer
  • Identifying and Testing Candidate Agents for Russian Olive Biocontrol, David Weaver
  • Implementing EDRR in Montana Using the INVADERS Database, Jane Mangold
  • Integration of Pathogens, Sheep, and Herbicides to Manage Cheatgrass, Fabian Menalled
  • Missouri River Watershed Coalition Coordination, Elizabeth Galli-Noble
  • Rangeland Revegetation Revisited, Jane Mangold        Saltcedar Effects on Mycorrhizal Fungal Communities and Screening of Native Species for Restoration, Erik Lehnhoff
  • Tall Buttercup Ecology and Integrated Management, Jane Mangold
  • Weed Free Borders Protection Program, Kim Goodwin
  • Weed Management Certification Program, Jane Mangold
  • Weed Seedling Identification Guide, Jane Mangold

Download a copy of the complete report 2013 MSU Annual Report to the MNWTF

Weed of the Week Series – Whitetop

Thursday, June 24th, 2010



Whitetop, also known as hoary cress was first identified in Montana in 1916.  It is native to northern Eurasia and has been introduced onto every continent in the world.  This plant probably arrived in North American via contaminated alfalfa seed.  Whitetop can be found in 54 of 56 Montana counties and infests a total of around 32,000 acres.  This plant is generally found in disturbed habitats that are associated with other weed species.


Whitetop is an herbaceous, relatively long-lived, rhizomatous perennial weed.  It tends to form dense monocultures, which displace native plant species and reduce biodiversity, wildlife habitat, and forage production.  Whitetop is of major concern because of the difficulty to control.  This plant has a root system similar to leafy spurge.  The root growth is rapid.  The vertical taproot can reach depths of 12-30 feet by the second or third growing season.  This taproot develops several lateral roots that eventually turn downwards and become taproots themselves often reaching greater depths than the parent taproot.  All of these roots develop buds, which turn into rhizomes and shoots.  This complex root system combined with the ability of a single plant to produce between 1,200 and 4,800 seeds each year are the reason that it is so difficult to control.  It is also a major concern because it can be toxic to cattle.


Growth begins early in the spring for this plant because it germinates in the fall.  Blue-green lance shaped leaves appear in a basal rosette very early.   The stem leaves are also a blue-green color with the lower leaves on stalks and the upper leaves clasping the stem.  The flowers are white and consist of four petals laid out in a cross.  The individual flowers are small but dense clusters of the flowers create the white, flat-top appearance.  The seed capsules are broad, flat, and heart-shaped.

What can you do?

If you have a small infestation hand pulling can provide control.  For the control to be successful all underground parts of the plant must also be removed and it may take 2-4 years for complete eradication.  Mowing the plant to ground level will reduce biomass and seed production but does not provide long term control.  Whitetop can be controlled using herbicides but it is difficult and requires aggressive reapplication.  Another option is using sheep to graze on this plant.  The best method for the control of Whitetop is an integrated weed management plan utilizing all of the above options with prolonged effort.  If you have any questions or think that you have a patch of Whitetop on your property call your local county weed district.

Visit the MWCA Weed ID pages for additional information and pictures of whitetop.

This series of articles was developed by Ravalli County.  If you would like to use these articles please contact Ravalli County Weed District Weed Coordinator at (406) 777-5842.

Hoary Cress Management (Cardaria sp.)

Friday, October 23rd, 2009


Celestine A. Duncan1, Weed Management Services and Mark J. Renz, New Mexico State University

Hoary cress (Cardaria sp.) is also known as whitetop or little whitetop. It is a deep-rooted, creeping perennial mustard that spreads by seed and vegetative root growth. There are three species including lens-podded hoary cress (C. chalapensis), heart-podded hoary cress (C. draba); and globe-podded hoary cress (C. pubescens). Hoary cress is well adapted to moist sites including sub-irrigated and irrigated pastures and hay-fields, rangeland, and disturbed sites such as roadsides, railways, and ditch banks. It can also invade cropland including small grain and alfalfa fields. Hoary cress may reduce crop yields, displace native plants, and reduce biodiversity, wildlife habitat, and forage production. The weed contains glucosinolates that can be toxic to cattle (McInnis et al. 1993). Hoary cress begins growth early in spring from a rhizomatous root system and flowers by April or early May. Seeds are produced about a month after flowering.

Link to Full Article