Submitted to: North Central Weed Science Society US Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 10/31/2010
Publication Date: 12/13/2010
Citation: Williams, M., Pataky, J.K. 2010. How safe is Capreno on sweet corn? North Central Weed Science Society US Proceedings. Available: http://www.ncwss.org/. Interpretive Summary:
Technical Abstract: Sweet corn hybrid sensitivity to postemergence herbicides was reported in the early 1990s with use of acetolactate-synthase (ALS)-inhibiting herbicides. Despite introduction of newer postemergence herbicides since that time, hybrid sensitivity has remained a problem. Recently a mutant cytochrome P450 (CYP) allele was shown to condition sensitivity to several of the P450-metabolized herbicides, including ALS-inhibitors and 4-hydroxyphenyl-pyruvate-dioxygenase (HPPD)-inhibitors. Even tembotrione, a relatively new HPPD-inhibiting herbicide, severely injures or kills hybrids homozygous for mutant CYP alleles, despite the product being formulated with safener isoxadifen. CaprenoTM was registered for use in sweet corn in 2010 and is a combination of tembotrione and thiencarbazone, a new ALS-inhibiting herbicide, plus isoxadifen. We evaluated the response of 434 sweet corn hybrids to a 2X rate of tembotrione+thiencarbazone applied postemergence to 4- to 6-collar corn. Four-hundred two hybrids had no injury or minimal injury (<5%) 10 to 12 days after application. Nine hybrids were severely injured (>50%) or killed by tembotrione+thiencarbazone, including: 177A, 3175, 0870 5770, Code 1038, DMC 20-38, GSS 5763, HMX 6386S, Merit, and UY 2587 OQ. All nine of these hybrids also were killed by applications of nicosulfuron in contiguous trials. Four of these hybrids are known to be homozygous for mutant CYP alleles. An additional 23 hybrids had low to moderate levels of mean injury (5 to 23%). Three of these hybrids are known to be heterozygous for a mutant and functional CYP allele. None of the 35 hybrids known to be homozygous for functional CYP alleles had more than 5% injury from tembotrione+thiencarbazone. Like tembotrione alone, tembotrione+thiencarbazone appears safe on hybrids homozygous for functional CYP alleles and is highly injurious to hybrids homozygous for mutant CYP alleles. Hybrids heterozygous for functional and mutant CYP alleles appear to be likely to sustain low to moderate levels of injury from tembotrione+thiencarbazone intermediate to either class of homozygous hybrids.