Vol. 54—2000 - NorthEastern Weed Science Society

SWEET CORN TOLERANCE TO NICOSULFURON AND CARFENTRAZONE
C. E. Beste'
ABSTRACT
PostemergenceherbicidesprovideIPMoptionsfor sweet com (Zea mays saccharata L.).
Nicosulfuronandcarfentrazonewereevaluatedwithnon-ionicsurfactantas postemergence
treatmentson severalsweet com varieties. Inthemid-Atlanticarea,othercropsareplantedafter
sweetcom harvest;therefore,postemergence herbicidesforsweetcom shouldnot affect
successivecrops. Nicosulfuronandcarfentrazoneappearto havethatcharacteristic.
Sweet com was planted in 36 inch row widths on May 4 and June II, 1999, in a Norfolk
loamy sand (0.6% OM) and sprinkler irrigated as needed. Preemergence herbicides, S­
metolachlor (0.78Ib ailA) and atrazine (1.0 Ib ailA) were applied to the May 4 planting, whereas,
only S-metolachlor (0.63 Ib ailA) was applied to the June II planting. Postemergence
treatments were applied at the fifth leaf collar stage-of-growth (approx. 29 days afier planting)
and the June II planting received an additional five day delayed post treatment at the sixth leaf
collar growth stage. The spray volumes on the May 4 and June II plantings were 31 and 17
gal/A, respectively. Non-ionic surfactant was added to all treatments at 0.25% VN.
Nicosulfuron at 0.031 and 0.062 Ib ailA, postemergence on the sweet com varieties,
'Bonus/Attribute' (yellow, Se) and 'GSS 9299' (yellow, Sh2) did not reduce yields with or
without husks. 'Sterling' (white, Su) yield with or without husks was unaffected by
nicosulfuron at 0.0621b ailA. Nicosulfuron, 0.1251b ailA postemergence to 'Bonus/Attribute',
'Sterling' and 'GSS 9299' did not reduce sweet com yields in the husk; however, only the yield
of 'Sterling' and 'GSS 9299' without husks was slightly depressed, which indicated a slightly
smaller cut-off com yield. The June II planting of 'Bonus/Attribute' was treated with
nicosulfuron, 0.0781b ailA and the yield with husk was not reduced; whereas, yield withont the
husk was reduced. The yield of varieties, 'Fantasia' (white, Se), 'Dynamo' (yellow, Su) and
'Esquire' (yellow, Su) were not reduced by nicosulfuron at 0.031 Ib ailA; however, rates of
0.062 and 0.125 Ib ailA caused yield reductions. 'Early Cogent'(white, Su) shoepeg-type sweet
com yields were not affected by nicosulfuron, 0.062 and O.l251b ailA. Sweet com injury
symptomswereprimarilychlorosis;however,tolerantvarietieshadmuchless chlorosisthan
susceptible varieties. Tolerant varieties may have 20 to 30'10growth reduction at the high rates
without a yield reduction; whereas, susceptible varieties hadyield losses. Carfentrazone,0.008
and0.0161b ailA, did not reduce growth or yields of 'Sterling' or 'Bonus/Attribute' sweet com.
Thecarfentrazoneinjurysymptomwas a bandof chlorosis acrossemergingleaves at the timeof
application.Nicosulfuron injurywas associatedwithdistortedstraightnessof kernelrows;
whereas,carfentrazonedid not affectkernelorientation.Applicationof nicosulfuron,0.125 lb
ailA at the sixth coUarstagedid not significantlyincreaseinjurycomparedto applicationatthe
fifthcollarstageof sweet com growth. Commercialcontrolof momingglory(Ipomoea spp.)was
providedby bothnicosulfuronandcarfentrazone.Yellow nutsedge(Cyperus esculentus L.) was
suppressedby nicosulfuron.
Nicosulfuronmaybe appliedpostemergenceonly to sweet com varietieswhichhave
demonstratedtolerance;whereas,carfentrazone, postemergence,appearsto have less potentialto
injuresweet com varieties.
'Assoc. Prof., Salisbury Facility, University of Maryland, Salisbury, MD 21801
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