Puncture Vine, Russian Knapweed High Priority On Area Noxious Weed Eradication List
Boise--County noxious weed managers in the Treasure and Magic Valley areas have set their sights on trying to eradicate two very troublesome invasive noxious weeds, including one that can be the curse of bicyclists, bare feet and pets, state noxious weed officials said today.
“County weed superintendents are zeroing in on attacking Puncturevine and Russian Knapweed, infestations of both of which are very common in southwestern and southern Idaho,” said Roger Batt, Idaho Weed Awareness Campaign coordinator.
Puncture vine, perhaps better known by its other name of “goathead,” is the particular bane of cyclists because the plant’s seeds have sharp, pointed spines that can easily puncture bike tires reducing the recreational potential of many areas. Goatheads can stick painfully in the bare feet of humans and animals, penetrate shoe soles and puncture light automobile and ATV tires.
Puncturevine is most often found on sandy, dry, or gravely sites. It is a summer annual broadleaf weed that generally grows low to the ground forming dense mats 2 to 5 feet in diameter. The stems radiate out from a central point at the taproot. Flowers are bright yellow with 5 petals. Cutting or pulling puncturevine at the root crown can effectively eliminate the plant. However, constant monitoring is necessary as this is a very rapidly growing plant.
Well-established populations have a large seed bank in the soil that can remain viable for up to 25-years according to weed control experts. Puncturevine can be controlled by hoeing or shallow cultivation. This should be initiated prior to flowering and seed production. Be sure to place all plants and their seeds into a trash receptacle.
A pre-emergent herbicide, such as Telar XP® can also be applied in the early spring to prevent this weed from growing. If the plant does become established, puncturevine is very susceptible to products containing 2,4-D. On driveways, sidewalks or other areas where you wish to have bare ground, herbicides containing Glyphosate, like Roundup®, are effective.
Russian knapweed is a bushy perennial, up to 4 feet tall. Its flowers are pink to purplish, about 1/2 inch in diameter and appear during the summer and fall. Russian knapweed is toxic to horses and causes chewing disease. It also can block out native vegetation and reduce grazing for animals. Russian knapweed can be very long-lived because it is so deep-rooted.
It can produce from 6 to 27 roots shoots per square foot, and roots may grow to a depth of 23 feet. It also likes to form dense colonies. “Controlling Russian knapweed can be a challenge. These plants spread by shoots (rhizomes) so controlling it by mechanical means such as hand pulling, shovel, plow, disk, etc., is fairly useless.” Batt noted.
Herbicides are generally recommended as the best course of action against Russian knapweed. Herbicides such as Milestone®, Curtail®, Redeem®, Transline®, and Telar DF® are the best ones to use. People using herbicides to control either puncture vine or Russian knapweed must be careful to always follow the label and safety instructions on that herbicide label and if necessary consult with a local pest control professional or their County Weed Superintendent.
Puncturevine and Russian knapweed are two weeds among the 67 noxious weeds listed in Idaho. Invasive weeds have already infested 8 million acres of Idaho’s lands and pose a serious threat to Idaho’s economy, ecology and agriculture, causing an estimated $300 million annually in direct damages. State and private landowners annually spend upwards of $30 million to combat noxious weeds.