Tolerance of sweet corn (Zea mays) hybrids to RPA 201772

Field studies at Arlington, WI, and LeSueur, MN, were conducted in 1996 and 1997 to evaluate tolerance of six sweet corn hybrids to RPA 201772 applied preemergence at 79 to 210 g/ha. Both years the most sensitive hybrid at th e Wisconsin site was 'Zenith,' with yield reductions of 14 and 22% at 210 g /ha (twice the labeled rate). 'Excellency,' 'Green Giant 43,' and 'Jubilee' tolerated RPA 201772 at 158 g/ha or less. The least tolerant hybrids in Mi nnesota were 'Green Giant 6' and Jubilee, and the most tolerant hybrids wer e Green Giant 43 and 'Rogers 9056.' Injury from RPA 201772 increased as app lication dose increased. The greatest risk of injury from RPA 201772 appear to be with Green Giant 6, Zenith, and Jubilee, especially on coarser textu red soils with low organic matter. Excellency, Green Giant 43, and Rogers 9 056 appeared to be the most tolerant. Because of the differential hybrid re sponse to RPA 201772 across sites and years, more hybrid response data need s to be generated before RPA 201772 is labeled in sweet corn.