HPIPM:Dyer's woad

Taxonomy

Domain	Eukarya
Kingdom	Plantae
Phylum	Magnoliophyta
Class	Magnoliopsida
Superorder	Rosanae
Order	Brassicales
Family	Brassicaceae
Genus	Isatis

Scientific Name

Isatis tinctoria

Common Name

Dyer's woad

Dyer's woad (Isatis tinctoria)

Author: Jim Jacobs, Plant Materials/Invasive Species Specialist, USDA-Montana NRCS.

Adapted from the USDA NRCS Montana Invasive Species Technical Note “Ecology and Management of Dyer’s Woad (Isatis tinctoria L.)”

Identification and Life Cycle

Dyer's woad (Isatis tinctoria) is a biennial member of the mustard family (Brassicaceae). The flowers of dyer’s woad are bright yellow with four petals. Stems reach 1 to 3 feet in height. Multiple floral stems per plant are common for dyer’s woad, and the combination of multiple stems with many branches bearing many bright yellow flowers gives dyer’s woad plants a showy appearance. The length of time from the initiation of flower stem growth to seed set is about eight weeks. The fruits are flattened, winged, longer than wide, 1/2 to 3/4 of an inch long and about 1/4 of an inch wide. They are green when they first form turning deep blue to black at maturity. Each fruit contains one brownish-yellow, cylindrical seed. Rosette leaves and stem leaves differ slightly in morphology. Rosette leaves grow up to 7 inches long with small-rounded teeth and are pubescent. Stem leaves clasp the stem, have entire margins, and are without hairs. All leaves have a prominent cream colored mid-rib extending the entire length of the leaf, and a bluish-green color. The leaf color and prominent mid-rib are good identifying characteristics of dyer’s woad. The weed has a thick, fleshy tap root that penetrates down to 3 feet into the soil. Lateral roots grow in the upper foot of the soil profile and are more predominant in the second growth season. The combination of tap root and lateral roots help dyer’s woad compete with annual and perennial plants for limited soil moisture, particularly in the fall and spring when soil moisture is greatest in semi-arid steppe regions.

Habitats

Dyer's woad invades rocky soil with limited water-holding capacity, and it is commonly found in rugged, inaccessible terrain. It has low nitrogen requirements enabling it to persist under stressed, nutrient-poor conditions. It can invade on well-maintained rangeland with relatively little disturbance, however competitive desired plants will retard its spread.

Impacts

Dyer's woad invades cropland, rangeland, and waste areas. It is highly competitive and can reduce cattle grazing capacity and crop and rangeland production.

Biology and Ecology

Dyer's woad typically germinates from seed in the spring, produces a rosette during its first growing season, overwinters via dormant buds on the root crown, flowers, produces seed, and dies in the spring of the second growing season. It has also been observed as a winter annual, germinating from seed in the fall and producing seed the following spring. Dyer’s woad population persistence and spread is dependent on seeds. Clonal growth has been observed but is not common. Dyer’s woad seeds are generally short lived, however when intact fruits are buried in the soil, the seeds can remain viable for many years. Dyer’s woad plants have been observed in plowed fields that had not been cultivated or supported dyer’s woad for over ten years. Leaf growth and rosette formation begins in the spring within one week of snowmelt, in many areas about the mid-April. Stem growth and inflorescence formation begins about two weeks later. The rapid spring growth rate and floral development help dyer’s woad compete in semi-arid steppe regions where soil moisture is most abundant at that time. Natural rosette mortality is greatest between mid-June and mid-September during periods of low precipitation and high temperatures. The length of time from the initiation of flower stem growth to seed set is about eight weeks.

Management Approaches

Control of dyer's woad can be accomplished through manual, mechanical, or chemical means.

Biological Control

Puccinia thlaspeos is a native rust pathogen that infects dyer’s woad and prevents seed production. First found in southern Idaho in 1978, P. thlaspeos has spread to most dyer’s woad populations in northern Utah. The rust can be maintained naturally in the dyer’s woad population for three years.

Mechanical and Cultural Control

In annual crops and row crops, tillage can be used to reduce dyer’s woad. Spring cultivation will kill rosettes and stop seed production. Crop rotation in combination with tillage and herbicide management should be used to control dyer’s woad and other weeds in alfalfa. Hand pulling, hoeing, and digging have been used to reduce populations of dyer’s woad. For hand pulling to be effective, the first treatment should be applied when the population is approaching full bloom.

Chemical Control

Herbicides should be applied to dyer's woad populations before flowering in spring.

Examples of herbicides that can be used to manage dyer's woad

Consult herbicide labels for additional rate, application, and safety information. Additional herbicide information can be found at http://www.greenbook.net.

Herbicide Active Ingredient trade name	Mode of Action	Product per Acre	Application Time or Growth Stage
Pasture, Rangeland, and Non-crop Areas
Chlorsulfuron	Inhibition of acetolactate synthase (ALS)
*Telar XP		1 - 3 ounces	Apply when dyer's woad is in the bud to early bloom stage in spring.
Metsulfuron methyl	Inhibition of acetolactate synthase (ALS)
*Escort XP		0.5 - 1 ounce	Apply when dyer's woad is in the bud to early bloom stage in spring.
Chlorsulfuron; metsulfuron methyl	Inhibition of acetolactate synthase (ALS)
*Cimarron Plus		0.625 - 1.25 ounces	Apply when weeds are less than 4 inches tall

The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.

References

For more information and images please visit IPM Bugwood. http://www.ipmimages.org/search/action.cfm?q=dyers%20woad