Control Whitetop (Hoary Cress)

(Cardaria draba (L.) Desv.)

Whitetop, or Hoary Cress, as it is known in the weed fighting community, is a serious problem throughout Idaho. This member of the Mustard family of plants, can be seen in fields, pastures, rangelands, waste areas, farmyards and roadsides .

Whitetop is a persistent, perennial plant that is so invasive, it can out compete even thick, healthy grasses. To see this, especially in the late spring, when the whitetop is in flower, look at some of the pastures and fields in the southwest Boise area. The whitetop is so dense in some places, there is little else in these fields.

We must protect our land from this weedy invasion!

There are two main reasons whitetop is difficult to control. First, whitetop creates large numbers of  viable seeds. These seeds can remain in the soil for several years, and germinate when conditions favor its growth. Second, established whitetop draws from the energy reserves stored in its root system to continue its growth each spring. New shoots, from the root crown, and from nodes on the roots, replace and increase the last years growth.

Because the roots play such an important part of what makes whitetop an invasive weed, we want to select herbicides that translocate (spread) throughout the plant, including the roots.

A number of chemicals can be effective on whitetop, including, Escort, and Telar DF, but these chemicals have different attributes that may make one of them a better choice than the others. The site characteristics, and any desirable vegetation there, also determine which herbicides should be used. Discuss your specific weed problem with a profesional, before you start purchasing your herbicides..

When you spray whitetop, it is important to know how your chosen herbicides work to control the plant. It is very common to spray too much herbicide on a plant. This can cause the foliage of the plant to be destroyed before the chemical has had time to move into the root system. If the roots do not recieve any, or enough, of the herbicide, it is possible for them to send up new shoot growth. For this reason it is important to follow the labels directions. The herbicide manufacturer knows how much of their product it takes to control a certain species of plant. Correct application rates keep you from wasting your time and money, as well as insuring that desirable plants are not damaged.

Call the Ada County  Noxious Weed Control office if you need assistance with whitetop control. Our phone number is (208) 577- 4646,  7:30 a.m. to 5:00 p.m. Monday through Friday. (except holidays)