Whitetop – The early bird of noxious weeds | TSLN.com

Whitetop – The early bird of noxious weeds

Jane Mangold and Gary Olsen

MSU photoWhitetop is a noxious weed that is toxic to cattle, is one of the first noxious weeds to appear in the spring and one of the first to warrant control.

BOZEMAN, MT – Are those white-topped plants weeds or flowers? If it is early spring, they’re probably weeds, and you should make plans to get them under control.

Whitetop is a noxious weed that is toxic to cattle. Also known as hoary cress, whitetop includes three species in the mustard family that are all members of the Cardaria genus. Though they can be confused when they are flowering with the native plant western yarrow, the native blooms later in the summer and has fern-like leaves. The three white-topped weeds are globed-podded whitetop, lens-podded whitetop and heart-podded whitetop.

The three species may grow close together. For example, all three types of whitetop have been found in Wheatland County. Because management of all three is similar, once you determine that you have whitetop, you don’t need to be too concerned with the exact species. Properly-timed management should prevent plants from producing seed pods and their associated seeds.

Whitetop is one of the first noxious weeds to appear in the spring and one of the first to warrant control. It frequently starts growing in early April and may bloom by late April to early May.

Whitetop is a deep-rooted perennial that may grow up to two feet tall.

Leaves are blue-green, arrowhead shaped and covered with soft white hairs. The base of each leaf clasps around the stem at the point of attachment. Plants have many small, white, four-petaled flowers, giving the plants a white, flat-topped appearance.

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Whitetop grows well in open, unshaded areas across a variety of soil types. Sub-irrigated pastures, rangeland, ditch banks, roadsides and waste areas are especially susceptible to invasion. Whitetop is also well-adapted to cropland, especially under irrigation. It reproduces from root segments and seeds, and is commonly spread by seed in contaminated hay or by dragging the root segments during farming practices. Once established, it can form dense stands.

Management of whitetop requires multiple integrated control efforts, the most important of which is to prevent its invasion into new areas whenever possible. Land owners should implement measures that limit seed dispersal and spreading of root fragments. Healthy stands of competitive vegetation can reduce whitetop’s invasion and spread. Detecting infestations when they are small and implementing a small-scale eradication plan using intensive control treatments will help to curb the spread of this weed on your land and across the state.

Diligent hand pulling or grubbing can provide control of very small infestations of whitetop. This requires complete plant removal within a couple weeks of weed emergence and should be repeated throughout the growing season for two to four years.

Mowing can help to reduce flowering and seed production, but will not provide long-term control. Mowing may help to increase the effectiveness of a subsequent herbicide application. Metsulfuron is the most effective herbicide on whitetop and can be found in a variety of products such as Ally, Escort, Cimarron or Chaparral. Herbicide should be applied to rosettes early in the spring or to fall regrowth. Successful control usually depends on an aggressive reapplication program. Always follow the product label to ensure proper use. No biological controls are currently available, however, research is underway and agents may be available in the future.

If you have whitetop on your land, it may be growing as you read this.

Don’t delay. Get your management plan ready for action.

BOZEMAN, MT – Are those white-topped plants weeds or flowers? If it is early spring, they’re probably weeds, and you should make plans to get them under control.

Whitetop is a noxious weed that is toxic to cattle. Also known as hoary cress, whitetop includes three species in the mustard family that are all members of the Cardaria genus. Though they can be confused when they are flowering with the native plant western yarrow, the native blooms later in the summer and has fern-like leaves. The three white-topped weeds are globed-podded whitetop, lens-podded whitetop and heart-podded whitetop.

The three species may grow close together. For example, all three types of whitetop have been found in Wheatland County. Because management of all three is similar, once you determine that you have whitetop, you don’t need to be too concerned with the exact species. Properly-timed management should prevent plants from producing seed pods and their associated seeds.

Whitetop is one of the first noxious weeds to appear in the spring and one of the first to warrant control. It frequently starts growing in early April and may bloom by late April to early May.

Whitetop is a deep-rooted perennial that may grow up to two feet tall.

Leaves are blue-green, arrowhead shaped and covered with soft white hairs. The base of each leaf clasps around the stem at the point of attachment. Plants have many small, white, four-petaled flowers, giving the plants a white, flat-topped appearance.

Whitetop grows well in open, unshaded areas across a variety of soil types. Sub-irrigated pastures, rangeland, ditch banks, roadsides and waste areas are especially susceptible to invasion. Whitetop is also well-adapted to cropland, especially under irrigation. It reproduces from root segments and seeds, and is commonly spread by seed in contaminated hay or by dragging the root segments during farming practices. Once established, it can form dense stands.

Management of whitetop requires multiple integrated control efforts, the most important of which is to prevent its invasion into new areas whenever possible. Land owners should implement measures that limit seed dispersal and spreading of root fragments. Healthy stands of competitive vegetation can reduce whitetop’s invasion and spread. Detecting infestations when they are small and implementing a small-scale eradication plan using intensive control treatments will help to curb the spread of this weed on your land and across the state.

Diligent hand pulling or grubbing can provide control of very small infestations of whitetop. This requires complete plant removal within a couple weeks of weed emergence and should be repeated throughout the growing season for two to four years.

Mowing can help to reduce flowering and seed production, but will not provide long-term control. Mowing may help to increase the effectiveness of a subsequent herbicide application. Metsulfuron is the most effective herbicide on whitetop and can be found in a variety of products such as Ally, Escort, Cimarron or Chaparral. Herbicide should be applied to rosettes early in the spring or to fall regrowth. Successful control usually depends on an aggressive reapplication program. Always follow the product label to ensure proper use. No biological controls are currently available, however, research is underway and agents may be available in the future.

If you have whitetop on your land, it may be growing as you read this.

Don’t delay. Get your management plan ready for action.