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Show New weed threatens Utah agriculture A weed that has gained a foothold in Utah could cause tremendous losses unless it's controlled soon, warns a researcher with the Utah Agricultural Experiment Station. The weed, leafy spurge, has already infested millions of acres in the U.S. and Canada, and approximately ap-proximately 1000 acres in northern Utah, says John Evans, a plant scientist with Utah State University. Univer-sity. "It's nearly impossible to kill the weed once it establishes extensive carbohydrate reserves in its roots," Evans warns. The weed, which is two-three feet high, throws seeds as far as 20 feet when seed pods burst, and also spreads via roots. New shoots develop even after topgrowth is removed. The drought-tolerant, herbicide-resistant weed eventually crowds out other plants on pastures and ranges. It is somewhat competitive com-petitive with cultivated crops. Currently approved herbicides offer only limited control, and more-potent, restricted herbicides are required. Researchers with the Experiment Station are testing new herbicides and helping develop effective biological controls. Cattle won't eat the weed. Sheep will eat the weed early in the grazing season, which apparently doesn't control the isolated patches of the weed, but may help limit spread on remote areas where the weed has crowded out other vegetation. The weed appears to be a hybrid of at least two species, a factor which has made control more difficult. Several types of insects have been released in other states in an attempt at-tempt to control the weed. "These insects do a reasonably good job in the plants they attack, but unfortunately they don't attack all plants," Evans says, an indication in-dication that insects detect differences dif-ferences in the chemical composition com-position of the weeds. USU researchers are using a unique type of mass spectometry to detect these chemical differences, information that will help evaluate the feeding preferences of insects considered as biological controls. USU weed control specialists hope to stem the spread of leafy spurge and avoid the damage associated with Dyer's woad, a weed that has spread rapidly over the state and is now found even on remote moun-taintops. moun-taintops. Leafy spurge seeds are not wind-borne so seed dispersal tends to be slower than with Dyer's waod. Actions during the next few years will determine how far the weed spreads. Evans says the weed probably has the potential of moving over the entire state, and will be particularly difficult to control once it infests rangelands. So far, most infestations are found on more accessible agricultural land. While it's too late to control the weed this year, Evans recommends identifying infested areas now for treatment next year. A leafy spurge conference involving in-volving researchers from several states was held July 10 in Wyoming. The threat posed by the weed -is reviewed in the Summer 1986 issue of "Utah Science," a quarterly publication of the Utah Agricultural Experiment Station. |