Vol. 54â2000 - NorthEastern Weed Science Society

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Frequent hand weeding reduced weed canopies to low levels on an intermittent basis. Weed regrowth occurred sporadically. Disease and insect damage sti1lresulted in losses of 50% or greater. Flower number and size and leaf number were equivalent to those plants whose weed canopies were chemically removed. Nearly all leaves supported three or more leaf lesions and 2 or more insect feeding sites. 40% of all corms were damaged beyond survival and few lateral conn buds could be harvested for commercial division. Plots treated with herbicides had significantly fewer insect feeding sites in May, June and July. Routine herbicide retreatment further reduced insect feeding damage to less than 25% of the expanded leaves. By August only 12% of the corms were irreparably damaged by iris borer. Plants in herbicide treated plots had fewer disease lesions but the overall surface area was not significantly different from that of untreated plants. Weed canopy or cleanliness significantly influenced losses associated with iris borer but did not appear to affect iris susceptibility to Didymellina leaf blight (Graph I). Insect and disease control applications were ineffective in suppressing damage when applied to control, hand weeded or weed infested plots (Table 2). Over-the-top or broadcast applications did not appear to deposit sufficient material on foliage nearJy hidden in the weed canopy. Broadcast applications did not improve insect and disease control and losses paralleled those of non-treated plants. Insect and disease control applications were initially effective when applied to plants in Dacthal- treated plots. As the summer progressed, however, weed breakthrough compromised targeted insect and disease applications and the actual amount of spray deposited on iris leaves rather than weeds remains questionable. Fungicides and insecticides provided excellent control when applied to plots previously treated with the pre/post herbicide combination. Sufficient crop contact and translocation occurred to insure adequate control and 88% or more of the crop survived. Plants averaged 6 or more divisible corms in August. CONCLUSIONS German Iris cannot be successfully produced without the combined inputs of weed, insect and disease control materials. Increasingly dense weed canopies winsuppress crop growth, flower number and flower size. Increasingly dense weed canopies will interfere with spray deposition and limit pesticide efficacies. Minimizing weed canopies will minimize iris borer leaf feeding and increase both conn survival and the number of potential divisions from those coons. Effective pre-season weed control will increase the success of insecticide applications and minimize the environment conducive to iris borer egg laying, feeding and development. Minimizing weed canopies had no appreciable effect of the occurrence ofleafblight but excessive weed canopies suppressed fungicide efficiency and therefore increased the severity of infection. The potential increase in relative humidity resulting from weed encroachment was not measured in this study but may account, in part, for the increases in disease severity in those plots with poor weed control. Despite a short crop sale season; continued attention to pest control will insure both crop survival and replication for later sales. A weed free environment will also ensure that far fewer iris borer eggs and larva and leaf blight lesions survive to aet as propagules in current or subsequent crop years. Additionally, a weed free field environment will also minimize the transfer of weed seed into pots and minimizethe amount of handweeding and lor herbicide applicatioms required during the spring of the crop sale year. 148
Table I Weed canopy, insect and disease infestationin GermanIris as affected by weed control WeedCanopy InsectFeeding#IL Diseaselesions#IL CormSurvival Treatment: June I July 1 MayI June 1 May I June1 August 1 Control 80 9.5 5.5 7.5 7.0 9.0 15% Handweed Ix 6.5 5.5 5.0 6.0 5.5 6.0 20% Handweed 5x 4.5 3.5 2.0 5.0 3.0 5.0 40"10 Dacthal
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WEED REMOVAL TIMING WITH ROUNDUP RE
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EFFECT OF HERBICIDE RATES AND IRRIG
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40 Effect of Pronone Applied with A
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Comparisonof Sulfosateand Glyphosat
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N 1175 feet Roundup Ready Studies R
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VIRGINIA TECH'S ONLINE WEED IDENTIF
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WEED CONTROL AND YIELD OF CUT FLOWE
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Table I. Effect of napropamide and
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The Effect of Total Postemergence H
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with commercial fertilizer. In gene
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HERBICIDE APPLICATIONS VERSUS HANDW
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exceeded 4. The success of training
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_u ____ Table2: Estimatesof herbace
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DOUBLE CROP CORN WEED CONTROL IN VI
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ANNUAL WEED AND GRASS CONTROL IN CO
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MANAGING QUACKGRASSINFESTATIONSAS C
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USING HERBICIDE RESISTANT HYBRIDS T
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NICOSULFURONIRIMSULFURON COMBINATIO
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GLYPHOSATE ALONE AND PRECEDED BY PR
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ROUNDUPVS. LIBERTY:WHATHAVE WE LEAR
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In summary, application timing for
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INFLUENCE OF TIMING ON WEED MANAGEM
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IMPACT OF GLYPHOSATE TIMING AND COR
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PREEMERGENCE HERBICIDES INFLUENCE W
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COMPARISON OF WEED CONTROL SYSTEMS
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Table I Mean Percent Weed Control V
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SMALL GRAIN WEED CONTROL - NEW WEED
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MODE OF ACTION, ABSORPTION, TRANSLO
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INFLUENCE OF CROWNVETCH WITH AND WI
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lRUMPETCREEPER, HONEYVINEMILKWEED,A
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FLUFENACET PLUS METRIBUZIN PLUS ATR
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CONTROLLING ASTERACEAE WEEDS WITH R
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0... Figure1. GerminationRateof Roo
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BIOLOGICALLY BASED WEED CONTROL STR
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NON·NATIVE VASCULAR FLORA OF BISCA
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principally in ruderal sites. lawns
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EVALUATION OF AZAFENlDIN FOR PREEME
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AUTOMATING MONITORING OF ROADSIDE W
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Table I: Swnmary of brush managemen
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Table I: Sequence codes and general
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IR-4 ORNAMENTAL RESEARCH PROGRESS F
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personnel with many of the illegal
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TOLERANCE OF ORNAMENTAL GROUNDCOVER
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MUGWORT CONTROL WITH CLOPYRALID AND
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POTENTIAL WEEDINESS OF SEVERAL NEW
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Table I: Identification, morphologi
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Trifolium tricolor 232 26 62 0 18 S
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NUTRIENT REMOVAL BY WEEDS IN CONTAI
Page 97 and 98: CONTROL OF POAANNUA FROM MULTIPLE S
Page 99 and 100: ANNUAL BLUEGRASS (PDaannual CONTROL
Page 101 and 102: LATERAL DEVELOPMENT OF PLANT oaowra
Page 103 and 104: RE-ROOTING OF FOUR VARIETIES OF CRE
Page 105 and 106: Table 2. Top growth weights (fresh)
Page 107 and 108: CONTROL OF DALLISGRASS IN COOL SEAS
Page 109 and 110: Kentucky bluegrass was rated to hav
Page 111 and 112: Table 2. Fresh weight (grams) barve
Page 113 and 114: MANAGING FENOXAPROP RESIST ANT CRAB
Page 115 and 116: ADVANCED FORMULATION TECHNOLOGY FOR
Page 117 and 118: Table I. Preemergence smooth crabgr
Page 119 and 120: 0.57EW at O.l21bs ai/A plus Confron
Page 121 and 122: EFFICACY OF DITHIOPYR FORMULATIONS
Page 123 and 124: EFFECTS OF DROUGHT ON THE INTERFERE
Page 125 and 126: WEED MANAGEMENT WITH HALOSULFURON I
Page 127 and 128: WEED CONTROL IN SWEET CORN WITH CAR
Page 129 and 130: COMPARISON OF USING LEAF AREA AND W
Page 131 and 132: RESULTS OF NEW YORK VINEYARD TRIALS
Page 133 and 134: HERBICIDE TOLERANCE IN CRANBERRIES
Page 135 and 136: Classification based on action on a
Page 137 and 138: EFFECTS OF SEVERAL POTENTIALLY USEF
Page 139 and 140: Supplement of the 53 rd Annual Meet
Page 141 and 142: with society activities to anyone.
Page 143 and 144: WINTER SQUASH CULTIVARS DIFFER IN R
Page 145 and 146: INCORPORATING QUINCLORAC IN AUTUMN
Page 147: Control efforts aim to eradicate bo
Page 151 and 152: Table 1: Percent mortality of respr
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Vol. 54â2000 - NorthEastern Weed Science Society

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Vol. 54â2000 - NorthEastern Weed Science Society