Published on March 28, 2014
1 Pesticide Recertification: Weed Issues Zac Reicher http://turf.unl.edu/ http://turf.unl.edu http://turf.unl.edu Weeds are: • “a plant out of place” • “anything growing where it is not wanted” • @#$#%&*(%$# • opportunistic • adaptable • aggressive • not understood Integrated Weed Management is: • not classical IPM • requires an understanding of the opponent and weapons available • chemicals are often the weapon of choice • some degree of failure is expected • not understood Weed ID • We are all not botanists • Critical issues for successful management/control – life cycle • annual or perennial – monocot/dicot (grass or broadleaf)
2 Summer Annuals (crabgrass, spurge, foxtail, purslane) Spring-Summer Germination Vegetative (Leaves) and Reproductive Growth (Flowering) Summer-Fall Seed deposited Summer Fall Death Winter Annuals henbit, chickweed, annual bluegrass Fall Seed germination and vegetative growth (leaves) Fall- Winter Dormancy Spring-Summer Initiate reproductive growth Seed deposition Summer Death Perennials (dandelion, nutsedge, clover) Spring-Summer Germination Summer Vegetative growth Fall-Winter Dormancy Spring/Summer Initiate reproductive growth Summer Sexual & vegetative reproduction
3 Excellent Weed ID References • Extension Publications • Distributors • Books • etc. Nebraska Department of Agriculture Bureau of Plant Industry P.O. Box 94756 Lincoln, Nebraska 68509 Order form available from: http://www.agr.state.ne.us/forms/nw11.pdf Crabgrass • Can produce 1000 seeds per plant • 1000 seeds/plant X 10% viable = 100 germinating seeds • 100 germinating seeds X 95% control = 5 plants August crabgrass control from April-applied preemergence herbicides over three years in studies at Purdue University. Applied to low-mowed Kentucky bluegrass to encourage crabgrass. August crabgrass control from April-applied preemergence herbicides over three years in studies at Purdue University. Applied to low-mowed Kentucky bluegrass to encourage crabgrass.
4 Single applications • Use high label rate • Apply as late as possible • Expect variable control Sequential applications of PRE’s • Improves consistency • Most effective in crabgrass hotspots • Generally ½ + ½ or ¾ + ½ (check label) • Should use same ai (1991) • Turns out that it doesn’t matter if you switch ai’s August crabgrass cover after split apps of the same or different PRE’s averaged over 4 locations (UNL 2011) 0 10 20 30 40 50 60 70 80 90 100 %Crabgrasscover(Aug) a a a a a a a a a cd e de c b b f Pendimethalin 3.8AC 1.5 lbs ai/A/app Prodiamine 65WDG 0.38 lbs ai/A/app Dithiopyr 2EW 0.25 lbs ai/A/app Changing ai for sequntial • More convenient • Maybe more economical • Expand the spectrum: Pendimethalin, prodiamine are a little better with summer annual broadleaves than dithiopyr • Could use dithiopyr for the sequential (late May-June) app regardless what or if PRE was applied in previous round to pick up germinating crabgrass in hotspots • Could limit weed resistance • Is weed resistance an issue? Effect of one or two applications of Drive or Tenacity on crabgrass control on a practice tee treated only with Drive the previous 8 to 10 years or in the adjacent rough that had not been treated by Drive (Purdue 2009) .
5 2,4-D susceptible 2,4-D tolerant After 2,4-D app and regrowth After 2nd 2,4-D app and regrowth After 3rd 2,4-D app and regrowth Limiting resistance • Maximize culture to limit weeds • Product selection • Mix ai’s • Alternate ai’s • Product timing • Product application
6 When using a rotary spreader, how much distance or overlap between passes? A: edge to edge (~0% overlap) B: Edge of pattern back to previous wheel track (50% overlap) C: overlap about 25% or so When using a rotary spreader, how much distance or overlap between passes? A: edge to edge (~0% overlap) B: Edge of pattern back to previous wheel track (50% overlap) C: overlap about 25% or so Broadleaf weed control • Sept-Oct best timing • At flowering in spring is OK 0 10 20 30 40 50 60 70 80 90 100 BroadleafWeedControl Nov 86 Rating May 87 Rating 24-Sep 8-Oct 17-Oct 22-Oct 30-Oct 11-Nov Application Date (1986) Fall broadleaf weed control on various application dates, rated in the fall and following spring. (Michigan State Univ. 1988) Fall broadleaf weed control on various application dates, rated in the fall and following spring. (Michigan State Univ. 1988)
7 Three-year mean of June ground ivy control from herbicides applied throughout the previous fall (Purdue 2007) 0 10 20 30 40 50 60 70 80 90 100 Sept 1 Sept 15 Oct 1 Oct 15 Nov 1 Nov 15 %Control Application Date Speed Zone 5 pt Speed Zone w/o carf. 5 pts Turflon 2 pts Turflon 2 pts + Gallery 1.33 lbs Vista 1.33 pts Yellow nutsedge • Germinates from tubers in early summer • Spreads via rhizomes throughout summer • Dies with frost • Tubers can lie dormant for many years • Tubers will regerminate multiple times if young plants are killed Yellow nutsedge • Basagran, Sedgehammer, Certainty, or Dismiss at best starting in June • Early applications may trigger regermination of tubers • Later applications may allow for tuber formation • Multiple apps are most effective • “Preemergence” doesn’t work • Eschelon (Dismiss + Prodiamine) at traditional crabgrass timing (early May)? • Stay tuned
8 Description • Monocot in the sedge family • Perennial, C4 species • Triangular stem http://www.ppdl.purdue.edu/PPDL/images/yellownutsedge 3.jpg Description: 3 Ranked Leaf Arrangement 1 2 3 Description • Fibrous root system with scaly rhizomes – Nutlets (tubers) form at the end of rhizomes • Photoperiods longer than 12 hours promote rhizome development and shoot production • Decreasing photoperiods promote rhizome tuberization (days start to shorten) Description • “Seed production is photoperiodically controlled. 12 to 14 hour photoperiods promote flowering and seed production, where as longer or shorter photoperiods are inhibitory.” – HOWEVER: controversy exists regarding the role of seed production in nutsedge propigation North American Distribution http://plants.usda.gov/java/profile?symbol=CYES Nebraska Distribution http://plants.usda.gov/java/county?state_name=Nebraska&statefips=31&symbol=CYES
9 Seed •Triangular in cross section •Brown to yellow to tan in color •Having a shiny or glossy seed coat Nutlets Individual Plants with Primary Tuber 2 Seedlings from 1 Nutlet Cultural and/or non-chemical Control • Equipment sanitation is important – Equipment that disturbs soil can move nutlets and rhizomes • Try to avoid infested soil if bringing new soil into a landscape • While yellow nutsedge does well in many environments (except highly arid environments), it does tend to thrive in moist environments – Drying areas of excessive moisture may help reduce the population • Persistent hand pulling can be effective if an infestation is small (depleting root stock reserves) Contaminated soil used for site renovation
10 Cultural and/or non-chemical Control • Yellow nutsedge is less competitive in shaded environments – Promoting vigorous turf growth or growth of other crops (fast canopy closure) should aid in reducing yellow nutsedge competitiveness • Research in onions in Oregon suggest that irrigation has a larger role in promoting yellow nutsedge growth relative to nitrogen fertilization – In turf, ensure the proper working of an irrigation systems and do not over water Chemical Control in Turf Post-emergence applications are thought to be most effective – Applications in the late spring to early summer are most effective • ALS herbicides – Halosulfuron (Sedgehammer) : warm & cool season turf – Sulfosulfuron (Certainty) : highly managed warm & cool season turf • PPO herbicides – Sulfentrazone (Dismiss) : warm & cool season turf – Bentazon (Basagran) : warm & cool season turf 2011 Study: ARDC (Mead, NE) • Effect of POST herbicide and timing on yellow nutsedge density and ground cover. • RCBD: 4 replications – High density, near monoculture • Density and % ground cover recorded every 2 weeks following the first herbicide application • Emergence started shortly prior to June 1 2011 Study: ARDC (Mead, NE) • Herbicide – Sedgehammer (1.33 oz) – Certainty (1.25 oz) – Tenacity (8 oz) – Dismiss (8 oz) – Basagran (2 pt) • Timing – June 11 – June 25 (No app. due to flooding) – July 9 – July 23 – August 6 CAUTION: First year of data and no statistical analysis yet to determine means separation PRELIMINARY results (% ground cover) 0 10 20 30 40 50 60 70 80 90 100 9-Jul 16-Jul 23-Jul 30-Jul 6-Aug 13-Aug 20-Aug 27-Aug 3-Sep 10-Sep 17-Sep 24-Sep 1-Oct 8-Oct 15-Oct %GroundCover Sedgehammer Untreated Timing 1 (June 11, 2011) Timing 2 (no app) Timing 3 (July 9, 2011) Timing 4 (July 23, 2011) Timing 5 (August 6, 2011) PRELIMINARY results (density) 0 20 40 60 80 100 120 PlantDensity(shoots/sqft) Sedgehammer Untreated Timing 1 (June 11, 2011) Timing 2 (no app) Timing 3 (July 9, 2011) Timing 4 (July 23, 2011) Timing 5 (August 6, 2011)
11 PRELIMINARY results (% ground cover) 0 10 20 30 40 50 60 70 80 90 100 9-Jul 16-Jul 23-Jul 30-Jul 6-Aug 13-Aug 20-Aug 27-Aug 3-Sep 10-Sep 17-Sep 24-Sep 1-Oct 8-Oct 15-Oct %GroundCover Dismiss Untreated Timing 1 (June 11, 2011) Timing 2 (no app) Timing 3 (July 9, 2011) Timing 4 (July 23, 2011) Timing 5 (August 6, 2011) PRELIMINARY results (density) 0 20 40 60 80 100 120 PlantDensity(shoots/sqft) Dismiss Untreated Timing 1 (June 11, 2011) Timing 2 (no app) Timing 3 (July 9, 2011) Timing 4 (July 23, 2011) Timing 5 (August 6, 2011) Summary • Control in turf settings are best accomplished with timely post-emergence herbicide application(s) • Promote vigorous turf growth and density to compete with yellow nutsedge • If applications are made early, follow-up applications may be necessary
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