Range Pasture Weed of the Week - Dalmation Toadflax

Early Detection and Rapid Response (EDRR) is a concept to identify potential invasive species prior to or just as the establishment of the invasive is taking place.  An Integrated Pest Management plan (IPM) can be developed to manage, contain and eradicate the invasive species before it can spread further. This will avoid costly, long-term control efforts.

Dalmatian toadflax is a perennial herb identified in parts of Nebraska, mostly in the Panhandle counties bordering Colorado, South Dakota and Wyoming.  Dalmatian toadflax is either a state or a local noxious weed in Colorado, South Dakota, Wyoming and other western states.

Dalmatian toadflax

a.k.a. – broadleaf toadflax, wild snapdragon, flaxweed 

Scientific name:  Linaria genistifolia ssp. dalmatica (L.)

Family:  Scrophulariacea (Figwort family)

Description

Origin:  Eurasia and Mediterranean. First reported in North America in the mid-1800s. It was brought to the U.S. as an ornamental, used as a yellow dye and for folk remedies. Dalmatian toadflax is distributed across most of Canada and the United States except the southeast.

Dalmatian toadflax is an herbaceous short-lived perennial herb. It reproduces / spreads by seed and underground rootstocks. Dalmation toadflax is a prolific seed producer. Large mature plants can produce up to 500,000 seeds per year. Seeds do not require a dormancy period before germinating and can remain viable in the soil up to ten years. Some seeds can germinate in the fall of the year, but most germinate in April or May of the following spring. Seed is spread by wildlife, vehicles, construction equipment, livestock, forages, feed grains, soil and gravel.

Dalmatian toadflax has an extensive root system. Lateral roots spread out ten feet from the base of the plant and can extend down four to 10 feet.

Dalmatian toadflax can grow to 0.6 to 0.9 meters (2 to 3 feet) in height.  The leaves are generally broad, spade-shaped with smooth margins.  The bases of the leaves wrap around the shoot.  The leaves are waxy, which reduces the ability of herbicides to move into the plant.

Dalmation toadflax flowers are in the axils of the leaves in a spike at the end of each stalk.  Flowers are yellow to orange in color and produces a two-cell fruit capsule, which contain the seeds.

Habitat

Dalmatian toadflax is adaptive to a wide range of environmental conditions. This plant favors disturbed sites and is found in rangeland, pastures, waste areas and roadsides. Dalmatian toadflax is very aggressive and competes with native vegetation for soil nutrients and water. This plant will dominate the affected site in time, leading to an eventual monoculture.

Dalmatian toadflax has no forage value for livestock. It contains a poisonous glucoside that is harmful to livestock.  Dalmatian toadflax is not harmful to sheep or goats.

Management

Prevention is the best and cheapest management option. Detect infestations early and keep from spreading. Having well-established grasses and forbs on a maintained pasture or rangeland with proper grazing and rotational grazing techniques can go a long way to prevent its establishment.  Scouting, monitoring and proper identification are key factors for management.  Infestations and spread of this weed can occur very rapidly.

Pulling or cultivating small Dalmatian toadflax plants can be an effective control method, as long as the plants are young, before they go to seed. The entire lateral roots need to be removed and an herbicide treatment may be necessary. Mowing alone will not control Dalmatian toadflax.  Timely mowing can reduce the amount of seed produced.

Grazing Dalmatian toadflax seedlings with sheep can help prevent establishment.  Grazing mature plants will not kill the plants and may stimulate new growth from the roots.  There are several insects that can have an effect on Dalmatian toadflax.  The beetle, Brachypterolus pulicarius feeds on the ovary.  Mecinus janthiniformus is a stem boring weevil that suppresses flower and seed production.  Two other weevils feed on the seed capsule, Gymnaetron antirrhini and Gymnaetron netum.  There is also a moth that defoliates up to 20 percent of the leaves on a single plant, Calophasia lunula.  These biological controls may reduce the infestation of Dalmatian toadflax, but they will not control it.  Other methods must be utilized in combination to reduce and control the infestation.

There are a few chemical treatment options available to manage Dalmatian toadflax. Products containing chlorsulfuron, dicamba, imazapic and picloram are shown to work.

Consult the specific herbicide label for instructions on how to treat Dalmatian toadflax for timing of application and rates. The waxy leaves and stems affect the coverage and uptake of the herbicides and cause erratic control. It is important to follow the product label unique to each individual herbicide.