Vol. 54—2000 - NorthEastern Weed Science Society

WEED CONTROL OPTIONS FORPOSTEMERGENCE CONTROL OF
TRIAZINE-RESISTANT WEEDS IN CORN
H. Menbere' andR. L. Ritter
ABSTRACT
Triazine-resistantcommonlambsquarters(Cbeno.,podiumalhwnL.) andsmoothpigweed
(Amaranthushybridus L.) continue to plague farmers throughout the mid-Atlantic region of the
U. S. It is estimated that these two plants can now be located in every county in Maryland. Their
spreadis dueto severalfactors;use of preemergenceherbicideprogramsthatdo not controlthese
pests, lackof controlof weed escapes,spreadingof manure contaminatedwithweedseed, and
customcombiningthatallows forseed dispersalin contaminatedequipment.
Preemergencecontrolof thesetwoweedsis limitedto a numberof products.
PendimehtaIin (Prowl - American Cyanantid) can provide fair to good control early in the season,
butresultshavebeen inconsistentin Maryland.Acetochlor(Harness- Monsanto,
SurpassffopNotch - Zeneca) may also provide some early season control. Flumetsulam (python
- Dow AgroSciences), flumetsulam combinations (Bicep TR - Novartis, BroadstrikelDual­
Novartis) and rimsulfuron + thifensulfuron-methyl (Basis - DuPont) have provided best
preemergencecontrol,butundercool, wet conditions,com (Za U1Ui L.) injurymayoccur
Under most growing conditions in Maryland, a timely application of a postemergence
com herbicide is usually justified, not only for control of triazine-resistant weedsbut for
peremtial broadleaf weed control as well. Dicamba (Banvel, Clarity - BASF), dicamba + atrazine
(Marksman - BASF), or combinations of dicamba with either primisulfuron-methyl (Beacon) or
primisulfuron-methyl + prosulfuron (Exceed) can provide good postemergence control of
triazine-resistantweeds andprovidegoodsuppressionof perennialbroadleafweedsas well.
Recently,a numberof newpostemergenceherbicides,herbicidepackage-mixesand
herbicidetank-mixeshavebeenstudiedfortheirutilityin thecontrolof triazine-resistantweeds.
Products under study that will be discussed include the following: diflufenzopyr + sodium salt of
dicamba (Distinct - BASF), primisulfuron-methyl + sodium salt of dicamba (NorthStar­
Novartis), nicosulfuron + sodium salt of dicamba (Celebrity Plus - BASF), and combinations of
pyridate (Tough - Novartis) or carfentrazone (Aim • FMC) with other tank-mix partners.
Agric. Tecb. Supvr. and Assoc. Prof., Agric. Exp. Sta., Dept. Nat. Res. Sciences and Land. Arch.,
Univ. ofMD, College Park, MD 20742.
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