Creeping jenny, green vine, corn lily, laplove, hedge bells, perennial morning glory, and devil’s guts — these are just some of the common names for field bindweed, a widespread pest on Utah farms and gardens with arrow-shaped leaves and small white flowers, that spreads by tendril across the ground and up the sides of fences or taller plants.
“Field bindweed is probably one of the most prevalent and one of the most hated noxious weeds in Utah," said Amber Mendenhall, the Utah State biocontrol coordinator. "It's found in all 29 counties. Most people are pretty familiar with it in yards, gardens, roadsides, but it's particularly a problem when we start talking about rangeland and agriculture.”
Biocontrol is the deployment of natural weed enemies to manage the spread of weeds when they become invasive. Mendenhall uses insects that feed on common weeds to reduce crop losses for farmers and gardeners.
“We have shown that a biocontrol agent is very specific to a host weed," Mendenhall explained. "When we select a problematic weed, we search out a natural enemy, and then we bring that natural enemy in to specifically attack that invasive weed.”
Scientists have estimated that economic losses due to field bindweed alone in the U.S. are counted in the hundreds of millions of dollars annually.
Specific numbers aren’t available for Utah, although almost all Utah counties report serious bindweed infestations. Mendenhall said that’s partly due to the unique abilities of bindweed to survive and reproduce.
“Field bindweed is a very long-lived perennial plant. It has roots … I haven't found the end of the roots yet," she said with a wry laugh. "So, it's a prolific root-spreading weed, has really pretty white flowers on it that can be quite attractive for a minute, until you realize that the vines will take over an acre in such a short time.”
Mendenhall said that bindweed seeds can survive for at least 60 years in the soil. This makes it nearly impossible to control with strategies like herbicides, tillage, hand weeding, or competition from other plants.
"We're at our wits end with field bindweed and that gives you the first impression of, well, what do we do now? Well, that's where biocontrol comes in," Mendenhall said. "This is really common with biocontrol in any system. We find that biocontrol works best when a weed has gotten so out of hand it has crested an economic and ecological threshold and we cannot control it, no matter how much funding or herbicide we put out there.”
Mendenhall has found that an unlikely ally can make a big difference in the never-ending battle with field bindweed.
“So, the field bindweed mite, he's my baby," she said, growing more animated. "The field bindweed mite is itty bitty. Smaller than a speck of dust. He's not an insect; he's an arthropod. He's eight legged, and you can only see him under the microscope.”
Researchers discovered that this mite has a unique dietary preference.
“They're very hungry, very prolific, and they have mouth parts that sucks the moisture right out of field bindweed leaves," Mendenhall explained. "They attack it on such a scale and such a rate that the field bindweed starts to lose energy, and slowly, over time, that field bindweed starts to lose enough energy that it dies. So these mites are slowly but surely taking out field bindweed plants.”
The mite won’t kill bindweed immediately, but Mendenhall said that the consistent presence of the mite over multiple years can have a dramatic effect on weed proliferation.
“Sometimes they really go out and shock us," she said, "and they reduce that field bindweed by 80% in three or four years. But more likely, you're going to see about a 50% reduction in flowering in a few years. Eight to 10 years out, you're going to see about a 50 to 60% reduction in field bindweed.”
Mendenhall said that biocontrol agents put weed control in an ecological context. They don’t completely wipe out the weeds, but they can bring them into balance.
“This is not a silver bullet, and this is not going to eradicate field bindweed," Mendenhall said. "As with all biocontrols, these insects or arthropod agents do not eat themselves completely out of house and home. So, you will see reduction of noxious weeds, but you will never see eradication.”
Field bindweed has the ability to steal soil water from many crop plants, which has concerning implications given Utah’s current climate pattern and water shortages. Still, Mendenhall is optimistic that the mite can continue to help us control bindweed in a changing climate.
“Field bindweed favors warm sites and does not mind arid conditions," she said. "So that lends you to believe that when we have hot, dry years due to weather or climate change, you're going to see more field bindweed, and you're going to see it do really well. The fun thing is, the field bindweed mite is one of the bio-control agents that also likes warm and arid sites. So, I think that this will actually be a good thing for the field bindweed mite. We may see more proliferation as time goes on.”