Damaging Oust level lower than thought on key Idaho crops

UI weed scientists have learned that the herbicide Oust—which moved on windblown soil particles from public lands to private cropfields in 2001— can damage sugarbeets and potatoes at far lower doses than previously suspected.Damages incurred in 2001 have been estimated at $15.1 million in sugarbeets, $80 million in potatoes,and $2.2 million in other Idaho crops.

Pamela Hutchinson and Don Morishita, from UI Aberdeen and Twin Fall Research & Extension (R&E) Centers, respectively, investigated the dosage harmful to these two susceptible Idaho crops because Oust can still be applied in Idaho to vanquish cheatgrass and other annual weeds.

Their results: It takes just 6 parts per trillion (ppt) to curb sugarbeet yields by 10 percent and just 60 ppt to halve them.At a projected 78 ppt, an increase in undersized, misshapen tubers and a decrease in U.S.No. 1-quality spuds cost potato growers $100 an acre. That’s less than the “no-effect level”of 100 ppt previously reported in research conducted elsewhere.“ Even below the analytical detection limit of 10 ppt in soil,we saw the effect on sugarbeets,” Morishita says.“We’re providing information that will be of value to everyone involved.”

--Marlene Fritz

© 2003 University of Idaho, College of Agricultural and Life Sciences.