Seedling puncturevine leaves pictured at top have hairs on each leaflet. Spiny fruit, below, have the punctures that break into
Puncturevine, a noxious weed to farmers and a nuisance to urban dwellers, continues to spread throughout north central Washington. With efforts to control the weed biologically a failure, it will take persistent, chemical spraying to halt its unwanted reach, says a weed control specialist.
The annual weed grows in a prostrate, matlike manner and can reach five to seven feet in diameter. Underneath the mat are hard, spiny burs that can lay dormant in the soil for up to six years, making eradication difficult. It grows in dry sites along roadways, ditch roads, edges of fields, and areas that are “beaten down, where other plants don’t want to grow,” said Clay Mackey, Chelan County Noxious Weed Board coordinator.
A problem area for orchardists is the bin collecting area in or near the orchard, Mackey said. Bins are set out on the orchard edges or near alleyways and can pick up the burs before being loaded for shipment to the packing house. “Those little seeds find a home in the bins and tires and down the road they go. That’s one of the main ways they are spread.”
Mackey, who spoke during the North Central Pear Day in Wenatchee, asked growers for help in stopping the spread of the noxious weed. “We need to be faithfully spraying along roads, ditchways, and driveways,” he said, adding that Chelan County sprays for puncturevine at least twice a year.
With seeds that can destroy bike tires, harm pet’s feet, and puncture skin when stepped on with bare feet or thin soles, it is a harmful public nuisance, he said.
It’s a tough weed to control because of its long dormant period. Puncturevine will germinate three or four times a year, depending on the amount of spring and summer rain received, he pointed out. “Annual plants have one reason to live, and that’s to produce more seed.”
“Biological control of puncturevine failed in Washington State,” Mackey said, adding that state officials tried both seed and stem weevils without success.
“The best control is persistent, multiple sprays made every year,” he said.
Another effective control method is grubbing the weeds out with a shovel and bagging the plant and seeds in a black, plastic trash bag for proper disposal. He suggested that for small areas, a good method of gathering up the seeds underneath the removed plant is to trap them on a terry cloth towel.
Mackey encouraged growers to stop during their day when they see the weed and go after it, either with a shovel or spray. And he suggested that growers spray for puncturevine when there is time, in between other orchard chores. He urged orchardists to work with their neighbors to control the weed along adjoining driveways or orchard entrances.
Although he didn’t make chemical recommendations, he suggested growers work with their chemical companies in choosing effective herbicides, matching the site and other weed species that may be present.
“If it sounds like I’m begging, I am,” he said. “This thing is out of control and really becoming a problem. I’m a one-man show and I’m asking for your help.”
County weed board budgets are stretched thin, he admitted, but noted that most counties are using herbicides with residual control. In Chelan County, he said that county workers will return to spray areas that show skips of missed control if the weed board is notified.
“The bottom line is that we’ve got to stop the spread,” he said.
Melissa Hansen is the research program director for the Washington Wine Commission. Hansen previously was an associate editor at Good Fruit Grower from 1996 through 2015.
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