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Nutsedge ( Cyperus spp.) Biology: Implications For Management. Dr. Theodore M. Webster Crop Protection and Management Research Unit USDA-ARS Tifton, GA. The Cyperaceae Family. Cyperaceae or the Sedges include 17 different genera
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Nutsedge (Cyperus spp.) Biology:Implications For Management Dr. Theodore M. Webster Crop Protection and Management Research Unit USDA-ARS Tifton, GA
The Cyperaceae Family • Cyperaceae or the Sedges include 17 different genera • Those species most commonly viewed as troublesome weeds are found in the Cyperus genus. • Of the 45 Cyperus species in the Southeast U.S., 29 are perennials • There are two primary perennial Cyperus spp. that cause economic losses.
Nutsedges: Important Crops or Important Weeds? • Purple nutsedge tubers were a staple in a late-Paleolithic (~16,000 B.C.) in Egypt. • Egyptian tombs dating to the 15th Century B.C. have been found to have recipes for ground tiger nuts (aka nutsedge tubers) mixed with honey. • Theophrastus (d. 287 B.C.): Egyptians boiled yellow nutsedge tubers in beer Negbi 1992
Nutsedges: Important Weeds • Purple nutsedge: identified as a weed growing in cropland areas in 1st Century A.D. • Purple nutsedge is considered the World’s Worst Weed. • Yellow nutsedge is one of the Top 5 World’s Worst Weeds. Negbi 1992 Holm et al. 1977
Yellow Nutsedge (Cyperus esculentus L.) Cold tolerance: 95% of tubers survived 2 C for 12 weeks when buried at 10 cm Distributed in areas where soil freezes Purple Nutsedge (Cyperus rotundus L.) Cold Intolerance: <10% of tubers survived 2 C for 12 wks at 10 cm Distributed in areas where soil freezes infrequently Southern Weed Science Society Weed Guide Stoller 1973
A Discussion of Nutsedges: • A tale of two tubers: why are nutsedges such persistent weeds? • A nutsedge is a nutsedge is a nutsedge? • 1 tuber then 10 tubers then 1000 tubers • How do I get rid of my nutsedges? • Are all mulches created equal? • Solarization: fact or fiction?
Why are nutsedges such persistent weed problems? • Estimated half life of a Purple Nutsedge tuber is 16 months • Predicted longevity of a tuber is 42 months • Burial at 8 and 23 cm did not affect tuber dormancy/viability Neeser et al. 1997
Persistence: Tubers or Seeds? • Purple nutsedge samples showed very limited intraspecific variation (RAPD). • Seeds were produced, but none germinated. • Yellow nutsedge samples showed a wide range of variation. • 17% of the flowers produced seed. • Viable seed produced 2 wks after full bloom. • 78% of the seed germinated. • Field studies indicate only 0.78% of seed established into a plant. Okoli et al. 1997 Lapham and Drennan 1990 Thullen and Keeley 1979
When Do Tubers Start to Form? • Tuber initiation: 6 to 8 Weeks After Foliar Emergence (same time as flowering). • Underground structures have more biomass than the aboveground foliage by 6 WAFE. • Tuber chains formed by 10 WAFE. • Long days stimulate: shoot, root, and rhizomes • Short days stimulate: tuber and floral production. Hauser 1962 Williams 1982
Reproductive Success! • Purple nutsedge planted at 1-ft intervals (43,560 plants/acre) produced in 1 season: • 3,090,000 plants/acre • 4,442,000 tubers and bulbs/acre • Cultivation in the second season did not affect the number of tubers and bulbs. • Heavy shading (72% shade) during the second growing season reduced tuber and bulb formation. Hauser 1962
Yellow Nutsedge Tubers: From 1 tuber 700 tubers produced after 6 Months of Growth
Competition for Light • Yellow nutsedge appears to be more tolerant of shade than Purple nutsedge • Yellow nutsedge biomass in 30% shade was not different than in full sunlight. • Purple nutsedge biomass was reduced in a linear with light. • Yellow nutsedge has a lower light compensation point (84 µmol m-2 s-1) than purple nutsedge (127 µmol m-2 s-1). Jordan-Molero and Stoller 1978 Santos et al. 1997
A Discussion of Nutsedges: • A tale of two tubers • A nutsedge is a nutsedge is a nutsedge? Or How can I distinguish these species? • 1 tuber then 10 tubers then 1000 tubers • How do I get rid of my nutsedges? • Are all mulches created equal? • Solarization: fact or fiction?
YELLOW NUTSEDGE: - Yellow florets - Blades: lighter green PURPLE NUTSEDGE: - Dark red/purple florets - Blades: deeper green
YELLOW NUTSEDGE: blade has a long, drawn-out tip PURPLE NUTSEDGE blade has a short, abrupt tip Three-Ranked Triangular-Shaped
YELLOW NUTSEDGE PURPLE NUTSEDGE Taster’s Choice
Purple Nutsedge: Tuber Chains Yellow Nutsedge: Tubers directly attached to mother plant
A Discussion of Nutsedges: • A tale of two tubers • A nutsedge is a nutsedge is a nutsedge? • 1 tuber then 10 tubers then 1000 tubers • How do I get rid of my nutsedges? • Are all mulches created equal? • Solarization: fact or fiction?
PURPLE NUTSEDGE YELLOW NUTSEDGE Objective: Evaluate the Spatial Dynamics of Yellow and Purple Nutsedge Expansion After 3 and 6 Months (From a Single Planted Tuber)
Yellow Nutsedge Purple Nutsedge
Yellow Nutsedge Patch Expansion: 6 months of growth from a single tuber Each Tick = 12.7 cm Scale 0 to 0.5 m Patch Area: 0.18 m2 177 Yellow Nutsedge Shoots Max. Density: 7000 shoots/m2 Each Tick = 12.7 cm Scale 0 to 0.5 m
Purple Nutsedge Patch Expansion: 6 months of growth from a single tuber Each Tick = 12.7 cm Scale 0 to 4.2 m Patch Area: 7.85 m2 518 Purple Nutsedge Shoots Max. Density: 280 shoots/m2 Each Tick = 12.7 cm Scale 0 to 2.0 m
0.18 m2 7.85 m2 Each Tick = 12.7 cm Scale 0 to 4.2 m Each Tick = 12.7 cm Scale 0 to 4.2 m Yellow Nutsedge Purple Nutsedge Each Tick = 12.7 cm Scale 0 to 2.0 m Each Tick = 12.7 cm Scale 0 to 2.0 m
Preliminary Conclusions • Purple nutsedge produced: • Similar number of shoots at 3 months • 2-fold more shoots than did yellow nutsedge at 6 months • Purple nutsedge expanded to a patch size 31-fold greater than yellow nutsedge • Yellow Nutsedge does not distribute itself far from the mother tuber
Take Home Message? • Confirms the predictions of a spatial model of yellow nutsedge growth: farming operations are the main cause of yellow nutsedge dispersal in the field (Schippers et al. 1993). • Purple nutsedge is well suited to distribute itself through its environment.
A Discussion of Nutsedges: • A tale of two tubers • A nutsedge is a nutsedge is a nutsedge? • 1 tuber then 10 tubers then 1000 tubers • How do I get rid of my nutsedges? Herbicides and Fumigants • Are all mulches created equal? • Solarization: fact or fiction?
Can We Predict Nutsedge Emergence? Yellow Nutsedge: 80% Emergence by 6 May 1999 and 30 April 2000 Purple Nutsedge: 80% Emergence by 1 June 1999 and 21 May 2000
Yellow Nutsedge Bentazon (75%) Metolachlor (55-75%) Glyphosate (55%) Halosulfuron (95%) Imazapic (80%) Imazethapyr (60%) Fomesafen PRE (85%) POST (60%) MSMA 1 lb ai/A (45%) 2 lb ai/A (90%) Purple Nutsedge Bentazon (20%) Metolachlor (<20%) Glyphosate (70%) Halosulfuron (95%) Imazapic (90%) Imazetheapyr (70%) Fomesafen PRE (35%) POST (?) MSMA 1 lb ai/A (30%) 2 lb ai/A (65%) Herbicides and Nutsedge Control
Purple nutsedge control was not improved when glyphosate was tank mixed with: chlorimuron imazaquin pyrithiobac Glyphosate at 1.0 kg/ha required 72 hrs to translocate to the tuber. Glyphosate at 2.0 kg/ha required 36 hrs. Glyphosate kills foliage and tubers directly attached to treated plants. Purple Nutsedge and Glyphosate Rao and Reddy 1999
Rain, Rain Go Away • Simulated rainfall at 1 and 24 hours reduced glyphosate efficacy on purple nutsedge 50 and 33%, respectively. • A rain-free period of 72 hours was needed to avoid loss of glyphosate activity. Bariuan et al. 1999
Quick Burn! Control? • Paraquat will quickly dessicate foliage and stop new tuber production, however the effects are temporary as new shoots will emerge from the tuber (Pereira et al. 1987).
Take Home Message? • Which nutsedge do you have? • Herbicide efficacy is often rate dependent; crop tolerance, weed efficacy, and economics dictate herbicide rate. • There are no quick fixes with nutsedges - Management of nutsedge species is a multi-year process.
Fumigants and Nutsedge Populations • Methyl Bromide: • 74 to 100% reduction in nutsedge numbers through plastic compared to UTC • (1,3-dichloropropene + Chloropicrin + Metham Sodium) and (Methyl Iodide): • Early: 76% and 91% Reduction • Late: 22% and 21% Increase • 1,3-dichloropropene + Chloropicrin: (Inconsistent results) • 90%+ Reduction in 1998 • 12% Reduction and 120% Increase in 1999 Webster et al. 2001
A Discussion of Nutsedges: • A tale of two tubers • A nutsedge is a nutsedge is a nutsedge? • 1 tuber then 10 tubers then 1000 tubers • How do I get rid of my nutsedges? • Are all mulches created equal? • Solarization: fact or fiction?
Nutsedge Crowfootgrass Polyethylene mulch suppresses weed growth, but creates a niche for nutsedges Nontreated Control: Polyethylene Mulch Nontreated Control: Bare Ground
Black plastic: 11% of yellow nutsedge shoots punctured and emerged through; tubers were produced. • Clear plastic: yellow nutsedge shoots did not puncture; caused yield reduction; tubers were produced. • IRT plastic: suppressed yellow nutsedge emergence; prevented tuber production. Etiolated shoots persisted for 6 to 8 weeks Majek and Neary 1991
Clear film: readily punctured by nutsedges when PAR was limited; Purple nutsedge (78%) more effective in puncturing clear mulch than yellow nutsedge (43%) (Chase et al. 1998). • Clear plastic allows weeds to grow, foliage pushes up the mulch 10 to 20 cm. (Majek and Neary 1991).
A Discussion of Nutsedges: • A tale of two tubers • A nutsedge is a nutsedge is a nutsedge? • 1 tuber then 10 tubers then 1000 tubers • How do I get rid of my nutsedges? • Are all mulches created equal? • Solarization: fact or fiction?
How deep are nutsedges distributed in the soil profile? Siriwardana and Nishimoto 1987 All within top 40 cm:Horowitz 1972
Lethal Temperatures for Nutsedge • Holt and Orcutt (1996): Tuber sprouting inhibited at constant temperatures above 44 C (2 wks). • Chase et al. 1999: Objective was to approximate actual field conditions. 45 C delayed nutsedge sprouting, required 50 C for inhibition (2 wks). Used Cycling Temperatures: 6 Hr. Hot and Cool to 26 C.
60 C for 30 minutes: 20% reduction 80 C for 30 minutes: 80% reduction 70 C for 30 minutes: 50% reduction 90 C for 30 minutes: 100% reduction
Objective: Characterize Relation Among Heat treatments, Duration of Exposure, and Nutsedge Tuber Viability Preparation of Nutsedge Tubers for Heat Treatments
LD50: 50C = <15 minutes 45C = 48 hours 35C = >96 hours
Preliminary ConclusionsLethal Temperature/Duration of Exposure: • Yellow Nutsedge: • 45 C for 8 hours = > 90% Tuber Viability • 50+ C for 15 minutes = < 50% Tuber Viability • Purple Nutsedge: • 50 C for 8 hours = > 70% Tuber Viability • 55 C for 4 hours = < 20% Tuber Viability • 60 C for 1 hour = < 5% Tuber Viability • How hot can we get our soils? • How long can they stay this hot?
Questions, Comments, Concerns? Twebster@tifton.cpes.peachnet.edu http://www.cpes.peachnet.edu/cpmru/Webster.HTM http://gaweed.com