Use of two imported insects could control two introduced weed species, bindweed and musk thistle.

From the Hillsboro Free Press, Hillsboro, Kansas, December 13, 2006


Field bindweed is an old pest for Marion County and much of the rest of the continental lower 48 states. But there's new hope in this area that it may jion another noxious weed, musk thistle, in beginning to succumb to the appetite of an introduced biological enemy.
If an insect culd slow down the plant that was introduced from Europe and the Mediterranean for erosion control and grazing, the strategy would save farmers and other landowner millions of dollars in herbicides, equipment time and personal time.
Rollin Schmidt, noxious weed director for Marin County, said the musk thistle weevil that Kansas State University was releasing into musk thistle patches in the early 1970s has begun to take control of the pasture pest.
He said a large portion of the musk thistle heads in Marion County this year had rotted out spots where seed should have been but where instead weevil larva fed, and emerged as adults.
The thistles can quickly crowd desirable grasses and forbes in pastures because cattle avoid their thorns giving them the chance to release thousands of wind-carried seeds.
The first step for biological control of bindweed just began in September.
Jeff Vogel, state weed specialist for the Kansas Department of
Agriculture, introduced bindweed gall mites into a bindweed patch on land farmed by his uncle, Randy Vogel, north of Marion.
The mites wee first introduced into the United States in Texas in 1989 through material from Greece, France and Italy.
Bindweed is so common and invasive, Jeff Vogel probably could have thrown a rock any direction in Marion County, and hit a patch of it.
But, Randy Vogel said, he was looking for something like a spot permanently planted in somthing like brome grass, with thick bindweed as an invadeer. He didn't want a location that a farmer might later want to till up.
The two men looked at one location, but finally chose a different one in a waterway because of its easy access for observation from a county road.
Randy said Jeff brought out four styrofoam cups of infested bindweed that he spded in at locations in the bindweed patch. He was also bringing infested bindweed to locate 50 miles away in theEl Dorado area.
They discussed how bindweed mainly is thought of as a pest for farmers, but it also is a major problem for persons like golf course managers.
Randy said the patch of bindweed, which extends from the waterway into the roadside, was especially competitive this year with other plants because of the dry weather.
Bindweed vines over other plants , and has fleshy sustaining root systems that can spread out 30 to 40 feet on individual plants, and go as deep as 30 feet, according to researchers. It can reduce crop yields as much as 50 percent or more.
Jeff Vogel warned that viewers of the newly infested bindweed patch can't expect to see immediate results. Biological treatments of pests develop over longer time frames compared to more easily massed produced chemical treatments, but their effects also tend to stay for the long-term.
Vogel said, "We more or less need to forget about the release site for a year or two, then come back and evaluate the release. It will just take that long for the mites to establish themselves to a point in which we can see some results."
The mites chew into the two-inch arrow shaped leaves and stem buds to form small roughened galls on the surface. The adults and nymph stages of mites can live in the galls for weeks. They can overwinter on root buds with the round, translucent eggs later deposited within the galls.
The damage to the bindweed first shows up as folded or twisted up leaves along the midrib, and on stem buds which fail to elongate.
Earlier Kansas researchers dating back to the 1920's tried to find biological control for bindweed starting with grazing animals.
Sheep grazed it if better grazing wasn't available, and pigs were found to find it highly palatable wiping out patches in three years as they enjoyed eating leaves and roots.
However, it was questioned whether thehigh calcite levels of bind weed was toxic for the hogs.
The researchers found Kansas bindweed resistant to 2-4D herbicide in 1964.
Human consumpton of bindweed dates back to A.D. 50 when a tea made from the seeds was found to cure spleen problems and the hiccups, but also caused blood in the urine by the sixth day and permanenet sterility by the 37th.
As for the musk thistle weevil, time has proved to be on its side. Researchers say it is well-established in most northwestern and northern plains states. They also have found that where larval infestations of the weevil exist in musk thistle, spraying with 2-4D doesn't significantly kill more musk thistle--that's probably good news.
The weevil eggs are deposited on flower bud bracts and stems in May and June to hatch in a week into larvae that feed from June to fall on seed heads and stems.
The gall mite is microsopic, but the musk thistle weevil can be seen as tiny black and yellow insects that emerge from the thistle flower head, then turn reddish-tan t black.