Sweet Corn Hybrid Sensitivity to Clopyralid

Abstract

Limited information exists on sweet corn tolerance to postemergence (POST) applications of clopyralid under Ontario growing conditions. Eight sweet corn hybrids were evaluated for tolerance to clopyralid in three field experiments conducted in 2001 and 2002 in Ontario. Clopyralid was applied POST at 200 and 400 g ai/ha, the proposed and twice the proposed registered rate for use in sweet corn in Ontario. Sweet corn response to clopyralid did not vary among the hybrids tested. In 2001, visual injury among hybrids 7 d after treatment (DAT) with clopyralid at 400 g/ha was less than 3%. Subsequent visual injury evaluations at 14 and 28 DAT showed no differences among sweet corn hybrids at either rate of clopyralid evaluated. The application of clopyralid at 200 and 400 g/ ha had no detrimental effect on plant height or marketable yield of any of the eight sweet corn hybrids. On the basis of visual injury, height, and marketable yield response ‘Calico Belle’, ‘CNS 710’, ‘DelMonte 2038’, ‘GG 222’, ‘GG 246’, ‘GH 2684’, ‘Reveille’, and ‘Rival’ are all tolerant to the POST application of clopyralid.

Tolerance of Eight Sweet Corn (Zea mays L.) Hybrids to Pyroxasulfone

“…However, none of the injury caused lasting damage and was not statistically significant. Visible injury did not increase significantly as herbicide rate increased and is consistent with previous studies on clopyralid (Soltani et al, 2005a) and topramezone (Soltani et al, 2007). This observation is in contrast to that observed when sensitive sweet corn hybrids were treated with bentazon (Diebold et al, 2004), isoxaflutole , mesotrione applied POST , nicosulfuron (Morton and Harvey, 1992;O'Sullivan et al, 2000), nicosulfuron plus rimsulfuron (O'Sullivan et al, 1995;O'Sullivan and Bouw, 1998), primisulfuron (O'Sullivan and Sikkema, 2002), prosulfuron (O'Sullivan and Sikkema, 2001), or thifensulfuron-methyl (Soltani et al, 2005b) in which injury increased with increasing herbicide rate.…”

Response of Eight Sweet Maize (<i>Zea mays</i> L.) Hybrids to Saflufenacil Alone or Pre-Mixed with Dimethenamid-P

“…ha -1 . Little visible injury seen in different sweet maize varieties evaluated in this study is similar with previous studies on clopyralid [21] and to a Abbreviations: su = sugary; sh 2 = shrunken endosperm mutant genotype; b Results are averaged for both locations and years; means followed by the same letter within a row for each treatment are not significantly different according to Fisher's Protected LSD test (P ≤ 0.05).…”

“…ha -1 . Lack of any height reduction between sweet maize hybrids evaluated in this study with saflufenacil and saflufenacil plus dimethenamid-p is similar to those found with other herbicides such as clopyralid, halosulfuron and topramezone [21,26].…”

“…Results in these trials are similar to findings with other herbicides such as halosulfuron which did not caused any negative impact on cob size at 1X or 2X of the proposed label dose for any of the sweet maize hybrids studied [26]. However, other studies have shown that cob size of susceptible hybrids can be reduced up to 67% with clopyralid or thifensulfuron-methyl [18,21].…”

“…ha -1 . Yield response with saflufenacil and saflufenacil plus dimethenamid-p are similar to yield response in other herbicides, such as clopyralid [21], topramezone [22] and halosulfuron [26] which were not adversely affected when the herbicide was applied at the label dose. However, other studies have reported significant injury in some sweet maize hybrids with certain herbicides.…”