How Can I Control Dyer's Woad?

Do you want to try controlling dyer's woad with cultural control methods?

Do you want to prevent dyer's woad infestation?

Do you want to control dyer's woad by hand roguing or digging?

Do you want to try controlling dyer's woad with biological control methods?

The most effective control measure for dyer’s woad is prevention. Cutting or mowing to prevent seed production can be effective, but this requires multiple passes. It is important to control new infestations of dyer’s woad before they become serious and widespread. Deep burial, removal and disposal, and burning of senescent, seed-bearing “skeleton” plants may assist in minimizing spread from localized infestations. However, dry seeds are easily detached from senescent plants, and care must be taken not to scatter these seeds about during destruction activities.

Hand roguing or digging individual plants is somewhat effective for small or scattered infestations. It may be necessary to continue removing new plants in an infested area periodically for at least two to three years. Hand removal is difficult because of the deep taproot, and the stems may break off when pulling allowing the plant to re-sprout new shoots. Therefore, depending on soil type, hand hoeing may be easier. If flowers or seedpods are present, plants should be uprooted, bagged, and removed from the field.

Solar tenting is a hydrothermal method of inactivating seeds on desiccated skeleton plants. Moistened seeds, enclosed within silicles, are susceptible to high temperatures, even though the silicle provides some protection to seeds, especially dry ones, against heat exposure. Germination can be greatly reduced or eliminated during the summer months by immersing seeds in water-filled plastic bags for several weeks. This approach is useful for remote or isolated infestations of dyer’s woad where on-site seed destruction is desirable to prevent spread.

Experimental trials evaluating a pathogenic rust fungus as a biological control agent of dyer’s woad have been conducted. Rust fungi cause foliar diseases that rarely eradicate all host plants, so their effects on weeds may be restricted to reduced plant vigor and reduced seed production. Therefore, the use of a rust fungus is likely to reduce, but not eliminate, dyer’s woad populations.

The most effective herbicides for dyer’s woad control are 2,4-D and chlorsulfuron. 2,4-D does not have soil activity and should be applied to seedlings or rosettes at 2 to 3 quarts per acre or a 1% solution for spot treatments. 2,4-D does not inhibit seed set when applied to flowering plants. Chlorsulfuron is more effective than 2,4-D but is restricted to professional use only. Regardless of the management program used, several years of control will be needed.