Vol. 54—2000 - NorthEastern Weed Science Society

EVALUATION OF AZAFENlDIN FOR PREEMERGENCE WEED CONTROL UNDER
GUIDERAILS
J.M. Johnson, A.E. Gover, and L.J. Kuhns'
ABSTRACT
A studywas establishedto evaluateazafenidinaloneandin combinationwithother
herbicidesforpreemergenceweed controlunderhighwayguiderails. The studywas located
along SR 33, near Nazareth, PA. Treatments were applied to 5 by 25 ft plots using a C02­
poweredbackpack sprayer equipped with a single Spraying Systems OC-12 spray tip, delivering
40 GPA at 34 psi, on May 6, 1999. Treatments were arranged in a randomized complete block
design with three replications. Treatments included an untreated check; 3.2,4.8,6.4, and 8 ovac
azafenidinaloneor in combinationwith either2.25 ozlac sulfometuronmethylor 102 ozlac
diuron; 2.25 o'Ziacsulfometuronmethylor 102 o'Ziacdiuronaloneandin combination;anda
commercial premix of 12.4 ovac imazapyr plus 100 ovac diuron 2J. All treatments except the
untreatedcheck included24 oz ae/aeglyphosate" to controlexistingvegetation. Greencover
ratings and cover by crownvetch (Coroni//a varia L.) were taken on May 13,7 days after
treatment (DAT); June 10,35 DAT; July 7, 62 DAT; August 5, 91 DAT; September 2, 119 DAT;
andOctober14. 161 DAT. Predominantweed species werecrownvetch,Canadathistle(Cirsium
arvense L.). prostrate spurge (Euphorbia humistrata Engelm), spotted knapweed (Cen/aurea
macu/osa Lam.), goldenrod(Solidago spp.),dandelion(Taraxacum officinale Weber),common
burdock (Arc/ium minus (Hill) Bernh), dropseed (Sporoboius vaginifiorus Torr.), kochia (Kochia
scoparia (L.) Scbrad.), and chicory (Chicorium intybus L.).
The baselinerating7 DAT accountedforvegetationpresentat treatment,andshowedthere
wereno significantdifferencesamongthetreatmentsat the initiationof the study,with average
greencover ratingsbetween 30 and55 percent. At the otherratingdates,from35 DATto 161
DAT, all treatments had significantly less weed cover thanthe untreated check. By 161 DAT,
4.8 ozlac azafenidin, 2.25 oziac sulfometuronmethyl,andazafenidinat either3.2 or 4.8 plus
diuronat 102 o'Zlachada significantlyhigherpercentageof weeds thanthebest treatments.
Althoughtherewere no statisticaldifferencesamongmost of the treatmentsafterthe 7 OAT
rating,by 161 DAT thereweretrends. At all ratesof application,azafenidin aloneprovided
controlcomparableto azafenidin plus diuron. Addingsulfometuronmethylto all ratesof
azafenidin providedless weed coverthanazafenidinalone. Thosetreatmentscontaining
azafenidinplus sulfometuronmethylhad4 percentor less greencoverby weeds even 161 OAT.
Similar studies performed in 1997 and 1998 also suggest that azafenidin plus sulfometuron
methylprovidesexcellent long tenn weed control. Azafenidinwould serve as a suitable
replacementfordiuronin the standard2.25 o71acsulfometuronmethylplus 102 ozlac diuronmix
usedin this experiment.
11ProjectAssociate, ProjectAssociate, and Professorof OrnamentalHorticulture,respectively,The Pennsylvania
StateUniversity,UniversityPark,PA.
2J Sahara,7.78% imazapyrplus 62.22%diuron,AmericanCyanamidCompany,Parsippany,NJ.
3/ RoundupPro, isopropylaminesalt of glyphosate, 3 Ibaelgallon, MonsantoCompany,St. Louis, MO.
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