PRE Weed Management Strategies

When Do Weeds Emerge?

SUMMER ANNUAL weeds can germinate in late winter (late February early March) and on into spring and summer if conditions are right.

PRE herbicides must be applied and activated before weed emergence.

Summer Annual GrassesSmooth Crabgrass Goosegrass Sandbur Yellow Foxtail

PRE Weed Management Strategies

When Do Weeds Emerge?

Most PRE herbicides used in turfgrass are for smooth crabgrass and goosegrass control. Many products are available that do a good job if they are applied on time. Many in the lawn care industry apply TOO LATE!

PRE Weed Management StrategiesWhen Do Weeds Emerge?

Soil temperature in the upper 0.5 inch of the soil profile needed for the following germinationSmooth crabgrass 55 degrees (mid to late March)Goosegrass 60 degrees (2 to 3 weeks later)Barnyardgrass 60 degrees (2 to 3 weeks later)Foxtail species 65 degrees (3 to 4 weeks later)

PRE Weed Management StrategiesWhen Do Weeds Emerge?

Many in the turf industry use biological indicators as guides for applying PRE crabgrass herbicides. This can lead to problems!

When dogwoods are in bloom smooth crabgrass may already be germinating. This is too late!

PRE Weed Management StrategiesWhen Do Weeds Emerge?

A better biological indicator would be to apply PRE crabgrass herbicides when forsythias are blooming. These tend to begin flowering in January February in the Raleigh area.

PRE Weed Management StrategiesWhen Do Weeds Emerge?

Some turf areas will warm more quickly in the spring than others. Pay attention to turf grown on sandy soils or south facing slopes. Grassy weeds will germinate sooner in these areas.

Unless the herbicide label states differentlyonly apply herbicides to well established turfgrass!!!

PRE Weed Management StrategiesWhen Do Weeds Emerge?

Applying PRE crabgrass herbicides early (January or sooner) usually will not affect the length of control, because the soil microbes that will eventually break down the herbicides are not active until soil temperatures increase.PRE crabgrass herbicides are effective for approximately 200 days once microbial activity begins.

PRE Weed Management StrategiesHerbicide Families

Dinitroanilines (DNAs)Excellent crabgrass, good goosegrass herbicidesUsually inexpensive and yellow in appearanceAbsorbed by roots and shoots growing through treated zoneAffect cell division sensitive plants dont surviveAre root inhibitors

PRE Weed Management StrategiesHerbicide Families

Dinitroanilines (DNAs)

Tolerant turfgrasses display root stubbing or root clubbing symptoms. Do not use these herbicides on athletic fields because of this. Roots can be sheared off due to heavy traffic and death can occur.

Photo Taken10-29-01

St. AugustinegrassNontreated

St. AugustinegrassBarricade 65WGSpring, 2001Clubbed roots

PRE Weed Management StrategiesHerbicide Families

Dinitroanilines (DNAs)

Have PRE and POST activityWill control crabgrass and goosegrass in the one leaf stage if watered in immediately (are forgiving herbicides if you apply a little too late)

PRE Weed Management StrategiesHerbicide Families

Dinitroanilines (DNAs)Benefin (Balan 2.5G)Benefin + trifluralin (Team 2G, Team Pro 0.86%)Benefin + oryzalin (XL)Prodiamine (Barricade 65WG)Pendimethalin (Pre-M, Pendulum WDG)Oryzalin (Surflan A.S.)

PRE Weed Management StrategiesHerbicide Families

PyridinesDithiopyr(Dimension, Dimension Ultra WSP)

Are not DNA herbicides but have the same mode of action (excellent crabgrass, good on goosegrass)Somewhat volatile works better as a granularControls crabgrass and goosegrass up to 3-4 leaf stage

PRE Weed Management StrategiesHerbicide Families

OxadiazolesOxadiazon(Ronstar G, Ronstar 50WSP)

Absorbed by shoots only, inhibits photosynthesisDoes not inhibit root growthTherefore, use this product in worn turf or where additional grow-in is desired (athletic fields)

PRE Weed Management StrategiesHerbicide Families

OxadiazolesOxadiazon(Ronstar G, Ronstar 50WSP)

Expensive (good crabgrass and goosegrass control)Provides NO POST crabgrass or goosegrass controlApply 10-14 days prior to weedy grass germinationCan use during sprigging or sodding of bermudagrass or zoysiagrass: NOT seeding

PRE Weed Management StrategiesHerbicide Families

AcetanilidesMetolachlor(Pennant Liquid)

Used more in ornamental beds than turfGood crabgrass, fair goosegrass controlAn exception: A PRE herbicide that DOES affect perennial structures (yellow nutsedge only)

PRE Weed Management StrategiesHerbicide Families

MixturesAre combinations of herbicide families that provide excellent crabgrass and good goosegrass controlOxadiazon + benefin(Regalstar)Oxadiazon + prodiamine(Regalstar II)Oxadiazon + bensulide(Goosegrass/Crabgrass Control)

Crabgrass sp. and Goosegrass(Preemergence Control)

Check labels for turf tolerancesMany Available Productsbenefin (Balan)benefin + trifluralin (Team Pro)bensulide (Betasan)dithiopyr (Dimension / Ultra)oxadiazon (Ronstar G)pendimethalin (Pre-M)prodiamine (Barricade 65WG)

PRE Weed Management Strategies Ken. Tall FinePer. Blue Fescue FescueRye.Balan T T M TTeam Pro T T M TDimension T T T T Ronstar T T NR T(Pre-M, T T T TPendulum)Barricade T T T TPennant NR NR NR NR Surflan NR T NR NR

PRE Weed Management Strategies Bahia Bermuda Centipede St. Aug ZoysiaBalan T T T T T Team Pro T T T T T Dimension T T T T TRonstar NR T NR T T(Pre-M, T T T T TPendulum)Barricade NR T T T T Pennant T T T T T Surflan T T T T T

Crabgrass sp. and GoosegrassPreemergence ControlAthletic Fields and High Traffic Areas

Avoid dinitroaniline herbicides and DimensionBalan, Team Pro, Pre-M, Barricade 65WGRoot inhibitors (affect turfgrasses also)Heavy traffic can shear rootsOptionsRonstar G

PRE Weed Management StrategiesSplit Applications

When using DNA herbicides and Dimension for summer grass control, turf managers have the option of making split applications.

At the proper timing, apply to 2/3 the single labeled rate, then apply the remainder 8 weeks later. Do not increase the TOTAL amount.

PRE Weed Management StrategiesSplit Application Advantages

In normal seasons, no differences will be observed. When environmental stresses do occur, the advantage will go to split applications.

South and east of Raleigh, splits are recommended because of earlier germination and longer growing season for summer annual grasses. (200 or more growing days)

PRE Weed Management StrategiesSplit Applications

Do not split oxadiazon (Ronstar) applications since it has no POST activity!!!

Even if you are a little late with the initial application, apply the full rate ASAP to obtain maximum PRE control for plants that have yet to germinate.

PRE Weed Management StrategiesPRE Grass Herbicides on Fall Established Turf

Unless the label says otherwise, apply PRE grass herbicides only to well established turf.

Generally, if turf was overseeded after October 15, do not use a PRE herbicide in the spring.

Turf tolerance depends on root growth below the treated soil layer.

PRE Weed Management StrategiesPRE Grass Herbicides on Fall Established Turf

Balan, Surflan, Team Pro labels advise against applications until 1 growing season has passed.

(Pre-M, Pendulum) can be applied after the turf has been mowed at least 4 times. The chemical barrier is thick (0.75) and the roots have to be below this barrier to ensure tolerance.

PRE Weed Management StrategiesPRE Grass Herbicides on Fall Established Turf

Barricade can be applied after the turf has been mowed at least 2 times or 60 days after overseeding. The chemical barrier is thinner than Pre-M, Pendulum (0.25) and the roots grow below this barrier more quickly.

Barricade is safer for newly planted grass than (Pre-M, Pendulum).

PRE Weed Management StrategiesPRE Grass Herbicides on Fertilizer Carriers

If PRE grass herbicides are used on fertilizer carriers, MAKE SURE that the herbicide and fertilizer timings are compatible to your turf situation.

Example: For a warm season turf, why buy a crabgrass / fertilizer material for a January February application. The grass is still DORMANT!! The nitrogen will not be utilized.

Summer Annual Broadleaf Weeds and Annual Sedge Annual Sedge Common Lespedeza Spotted Spurge Prostrate Knotweed

PRE Weed Management StrategiesSummer Annual Broadleaf Weeds and Annual Sedge

Many of the PRE summer annual grass herbicides have activity on small-seeded summer annual broadleaf weeds and annual sedge. The timings are ideal for controlling many types of weeds with one product at one time if you can identify weed populations correctly.

PRE Common Lespedeza ControlDimension

PRE Spotted Spurge Control DimensionRonstarSurflanTeam ProXLPre-M, PendulumBarricade

PRE Prostrate Knotweed ControlDimensionPre-M, PendulumSurflanTeam ProXLBarricade

PRE Annual Sedge ControlRonstar

PRE Weed Management Strategies Isoxaben (Gallery Dry Flowable)

Gallery Dry Flowable is the only TRUE PRE broadleaf herbicide labeled in turfgrasses. This herbicide has very limited activity on grass plants.

All established turfgrasses (cool and warm season) are tolerant.

PRE Weed Management Strategies Isoxaben (Gallery Dry Flowable)

Gallery Dry Flowable provides PRE control of summer annual broadleaf weeds such as spotted spurge and prostrate knotweed (late winter early spring applications), along with many winter annual (late summer early fall applications) and perennial broadleaf weeds germinating from seeds when properly applied.

PRE Weed Management Strategies

When Do Weeds Emerge?

WINTER ANNUAL weeds can germinate in late summer (late August early September) and on into winter and spring if conditions are right.

PRE herbicides must be applied and activated before weed emergence.

Weed BiologyWinter Annual Weed Examples

GrassesBroadleavesAnnual bluegrassChickweed species(Poa annua)HenbitLawn burweedSpeedwell speciesKnawelHop clover

PRE Poa annua Control in Warm-Season Turf Overseeded With Perennial RyegrassBalan120 lb/acreApply 6 weeks before overseeding

Dimension Ultra WSP1.25 lb/acreApply 8 weeks before overseeding(NCSU data suggest 6 weeks before better)

Target early to mid October for overseeding

PRE Poa annua Control in Warm and Cool-Season TurfIf warm-season grasses are already overseeded, or cool-season grasses already reseeded or newly seeded, do not apply PRE poa annua herbicides

Germinating seedlings will be affected!

PRE Poa annua Control in Established Warm and Cool-Season TurfTeam Pro100 lb/acrePre-M, Pendulum3.34 lb/acreBetasan, Bensumec, PreSan12.5 lb ai/acreBarricade 65WG0.75 lb/acreRonstar G100 lb/acre

Along with Balan and Dimension / Ultra WSP, these products are all labeled in established tall fescue, Kentucky bluegrass, perennial ryegrass, bermudagrass, St. Augustinegrass and zoysiagrass.

PRE Weed Management StrategiesWinter Annual Broadleaf Weeds

Many of the PRE summer and winter annual grass herbicides have activity on small-seeded winter annual broadleaf weeds. The timings are ideal for controlling many types of weeds with one product at one time if you can identify weed populations correctly.

Common ChickweedBarricade(Pre-M, Pendulum)SurflanTeam Pro, XLHenbitBarricade(Pre-M, Pendulum)SurflanDimension, XL

Lawn BurweedNone of the PRE grass herbicides are effective.Corn Speedwell(Pre-M, Pendulum)Dimension***Barricade and Ronstar control some speedwell sp.

KnawelNone of the PRE grass herbicides are effective.Hop Clover(Pre-M, Pendulum)

PRE Weed Management Strategies Winter Annual Broadleaf Weeds

Gallery Dry Flowable provides PRE control of winter annual broadleaf weeds such asHenbitCommon chickweedSpeedwell species

PRE and POST Weed Management Strategies for Poa annua ControlHerbicide Families

AmidesPronamide (Kerb WSP)

Kerb WSP enters poa annua mainly by root absorption but also is absorbed through shoots.

PRE and POST Weed Management Strategies for Poa annua ControlKerb WSP

2 to 3 lb/acreApply September 15 through February 1Do not overseed for 90 daysTolerance in bermudagrass, zoysiagrass, centipedegrass and St. AugustinegrassProduct is mobile if heavy rain or irrigation!

PRE and POST Weed Management Strategies for Poa annua ControlEthofumesate (Prograss)

Tolerance in dormant bermudagrass overseeded with perennial ryegrass or established perennial ryegrass turf2.67 qt/acre 30 to 45 days after overseeding2.67 qt/acre 21 to 28 days after 1st applicationDo not apply after January 1 greenup concerns

PRE and POST Weed Management Strategies for Poa annua ControlEthofumesate (Prograss)

Prograss is mainly shoot absorbed but can enter through roots.

Specialized Poa annua Control Programs Overseeded Bermudagrass Putting Greens

Apply fenarimol (Rubigan) 2 to 3 times in late summer / early fall with last application being

14 days prior to overseeding ryegrass28 days prior to overseeding Poa trivialis

Specialized Poa annua Control Programs Bentgrass Putting Greens

Apply bensulide (Betasan) twice in the fall and once in the winter. The initial fall application must be made prior to poa annua germination.

This program will not control perennial types!

Specialized Perennial Poa Control Programs Bentgrass Putting Greens

Plant growth regulators (PGRs) should be used in the fall and spring to shift competition to favor bentgrass. This approach could take 3 to 5 years for acceptable conversion.