Herbaceous weed control (HWC) during the spring following planting longleaf can be critical to growth and survival on old-field, pasture, hayfield, and cut-over sites, particularly in droughty years.
♦ HWC can increase percentage of seedlings out of the grass stage by the 2nd year.
♦ A four to six foot wide band is often as effective as a broadcast treatment.
♦ Wait at least 2 months and with 1 to 2 inches of new feeder root growth from 2 to 3 or more lateral roots to spray herbicides over-the-top of longleaf after planting.
HERBICIDES FOR CONTROL OF BROADLEAF WEEDS AND GRASSES
(all treatments applied over-the-top of pines unless noted otherwise)
ARSENAL® (BASF; 53% imazapyr; 4 lb per gal)
♦ Very effective on perennial grasses, including difficult to control species like
♦ Bermudagrass, seedling Johnsongrass and Panicums
♦ Weak on broadleaf weeds in the composite group (see Oust XP®) and legumes
♦ Effective on established weeds
Apply 4 – 6 fluid oz product per acre
♦ Do not add surfactant
♦ Optimum timing: Early post to post emergence of weeds (April – May)
♦ Grass and broadleaf weed control including, but not limited to: bahiagrass, barnyardgrass, bluegrass (annual, Kentucky), Bermudagrass, crabgrass, fescue, foxtail, Italian ryegrass, Johnsongrass, lovegrass, panicum (fall), sandbur, smooth brome, wild barley, wild oats, witchgrass, camphorweed, carpetweed, chickweed, clovers, cocklebur, dandelion, dogfennel, horseweed, goldenrod, knotweed, lambsquarters, milkweed, ragweed (common, giant), pepperweed, pigweed, plantain, pokeweed, purslane, pusley (Florida), shepard’s purse, stinging nettle, sowthistle, annual spurge, sunflower, tansymustard, wild carrot, wild parsnip, wild turnip
OUST® XP® (DuPont; 75 % sulfometuron methyl)
♦ Very effect on a broad spectrum of broadleaf weeds, including composites
♦ Weak on perennial grass including Bermudagrass, broomsedge, and some Panicums (see Arsenal AC®)
♦ 1st Year plantings: apply 2-4 oz Oust product per acre
♦ Optimum timing: Pre-emergence (March-April)
♦ Do not use Oust when soil pH > 6.2
♦ Grass & broadleaf control including, but not limited to: chickweed, crabgrass, dogfennel, fescue, fireweed (willowweed), goldenrod, horseweed, Kentucky bluegrass, nutsedge (yellow), Panicum (broadleaf), pokeweed, ragweed, shepherd’s purse, white snakeroot, yellow sweetclover, annual bluegrass, barnyardgrass, foxtail barley, foxtail fescue, Italian ryegrass, jointed goatgrass, bromes (red, ripgut), reed canarygrass, signalgrass, yellow foxtail, mustard, pepperweed, pigweed, sunflower, vetch, wild carrot, wild oats
OUST XP (DuPont; 75% sulfometuron methyl) + VELPAR L® (DuPont; 25% hexazinone)
♦ Broad spectrum weed control of broadleaf weeds and most grasses, weak on Bermudagrass and broomsedge
♦ Hexazinone may cause pine seedling mortality on sandy sites and on sites with low organic matter (old-field sites), ensure proper calibration and follow label directions regarding appropriate rates for various soil types
♦ Do not use Oust when soil pH > 6.2
♦ Apply 2-4 oz Oust product + VELPAR L 2 – 3 pints (or Velpar DF 10 – 16 oz product) per acre depending on soil texture (see product label)
♦ Optimum timing: Pre to early post emergence of weeds (March – early May)
♦ Use low rate of Oust + Velpar L or Velpar DF on coarse textured (sand, loamy sand, and sandy loam) soils and where soils are low in organic matter (see label)
♦ Grass & broadleaf control including, but not limited to: chickweed, crabgrass, dogfennel, fescue, fireweed (willowweed), goldenrod, horseweed, Kentucky bluegrass, nutsedge (yellow), Panicum (broadleaf), pokeweed, ragweed, shepherd’s purse, white snakeroot, yellow sweetclover. annual bluegrass, barnyardgrass, foxtail barley, foxtail fescue, Italian ryegrass, jointed goatgrass, bromes (red, ripgut), reed canarygrass, signalgrass, yellow foxtail, mustard, pepperweed, pigweed, sunflower, vetch, wild carrot, wild oats, asters, brackenfern, fleabane
OUSTAR® (DuPont; 11.8% sulfometuron methyl and 63.2% hexazinone)
♦ Similar to Oust XP + Velpar products as above, but in a packaged mixture
♦ The ratio of active ingredients is set; hexazinone rate tend to be too high on sandy and low soil organic matter sites
♦ 1st Year weed control application product rates per acre:
10-12 oz Course textured soils (sand, loamy sand, sandy loam)
12-16 oz Medium textured soils (loam, sandy clay loam, silt loam)
16-19 oz Fine textured soils (clay loam, sandy clay, silty clay loam, silty clay)
♦ After 1st year weed control application product rates per acre:
12-16 oz Course textured soils
16-19 oz Medium textured soils
18-24 oz Fine textured soils
♦ Do not use Oustar when soil pH > 6.2
♦ Optimum timing: Pre to early post emergence (March – early May)
♦ Grass & broadleaf control including, but not limited to: chickweed, crabgrass, dogfennel, fescue, fireweed (willowweed), goldenrod, horseweed, Kentucky bluegrass, nutsedge (yellow), Panicum (broadleaf), pokeweed, ragweed, shepherd’s purse, white snakeroot, yellow sweetclover
VELPAR DF (DuPont; 75% hexazinone)
♦ May cause mortality where excessive rates are applied on sandy soils and/or soils with low organic matter, ensure proper sprayer calibration to apply precise herbicide rate per acre, following label recommendations regarding specific herbicide rates for various soil types
♦ 1st Year weed control application product rates per acre (the same amounts can be applied in years 2, 3, and 4):
1 1/3 lb Course textured soils (loamy sand, sandy loam)
1 1/3 – 1 ½ lb Medium textured soils (loam, sandy clay loam, silt, silt loam)
1 ½ – 1 4/5 lb Fine textured soils (sandy clay, silty clay loam, silty clay, clay, clay loam)
♦ Weed control application product rates per acre for established trees (≥ 4-yrs-old):
1 1/3 – 1 2/3 lb Course textured soils
1 2/3 – 2 1/3 lb Medium textured soils
2 1/3 – 2 2/3 lb Fine textured soils
♦ Optimum timing: Pre to early post emergence (March – early May)
♦ Grass & broadleaf control including, but not limited to: Asters, barnyardgrass, annual bluegrass, brackenfern, bromegrass, fleabane, foxtail, horseweed, ragweed, ryegrass
VELPAR L (DuPont; 25% Hexazinone)
♦ May cause mortality where excessive rates are applied on sandy soils and/or soils with low organic matter, ensure proper sprayer calibration to apply precise herbicide rate per acre, following label recommendations regarding specific herbicide rates for various soil types
♦ 1st Year weed control application product rates per acre (the same amounts can be applied in years 2, 3, and 4):
21 to 32 oz Course textured soils (loamy sand, sandy loam)
24 to 40 oz Medium textured soils (loam, sandy clay loam, silt, silt loam)
28 to 48 oz Fine textured soils (clay, clay loam, sandy clay, silty clay loam, silty clay)
♦ After 4th year weed control application product rates per acre:
21 to 40 oz Course textured soils
28 to 56 oz Medium textured soils
36 to 64 oz Fine textured soils
♦ Optimum timing: Pre to early post emergence (March – early May)
♦ Grass & broadleaf control including, but not limited to: Asters, barnyardgrass, annual bluegrass, brackenfern, bromegrass, fleabane, foxtail, horseweed, ragweed ryegrass
Also consider:
(1) The herbicide purchaser and applicator need to look closely at the herbicide label to make sure that the herbicide product used is: (a) labeled for the particular use site (e.g. “for use in forest sites”, “for use in conifer plantations”, etc.) (b) labeled for the pine crop species (or genus in some cases), and (c) labeled for the particular application (“herbaceous weed control in pine plantations”, “ herbaceous release”, etc.). Herbicide products, even those with the same trade name (such as “Roundup”), may have different amounts of the active ingredient per gallon, so always follow the rates specified on the label of the particular container being used.
(2) Remember rates are per acre treated. Here are two examples of calculating the herbicide needed for a banded herbicide application using 10 oz Oustar product per acre treated, assuming 12 feet between the rows: (a) spraying a 4 foot wide band, 10 oz Oustar will take care of 3 acres total land area. In effect, one acre is banded and two acres are untreated, so herbicide is applied to one-third of the area. A total of 400 oz (25 lbs) of Oustar would be needed for a 120 acre field where one-third the area is treated in bands. (b) When spraying a 6 foot wide band on rows 12 feet apart, 10 oz Oustar will take care of 2 acres total land area. One acre is banded and one acre is untreated, so herbicide is applied to half the area. A total of 600 oz (37.5 lbs) of Oustar would be needed for a 120 acre field where herbicide is applied to one-half the area in bands.
(3) There are generics for some of the above listed herbicides and various product labels for the same active ingredient do vary. Read the product labels to make sure that your intended use is consistent with labeling.
Please read and follow all label recommendations. Inclusion of a product trade name or a company name in this publication does not constitute an endorsement of a product or a company, as other products manufactured by different companies might be equally suited for the intended herbicide use.
HERBICIDES FOR CONTROL OF ANNUAL & PERENNIAL GRASSES ONLY
(1) When restoring native grasses concurrently to establishing longleaf pine, be careful not to apply the following “grass herbicides” in the Warm Season Native Grass (WSNG) planting area after grasses have emerged.
(2) All grass control herbicides listed below are postemergence, foliar active herbicides.
(3) Best control for all grass species is obtained when grasses are in an early growth stage. For Texas panicum, apply when the grass is less than 4 inches tall. For Bermudagrass two applications are usually needed; the first when less than 6 inches tall and a second when re-growth is less than 4 inches. Multiple applications are also needed for Johnsongrass.
(4) Herbicides in this group generally do not mix well with other herbicide products. However, it is very important to add surfactants (wetting agents) to improve plant uptake. See information below and product labels for details.
(5) Herbicide spray solution (water) volumes are typically between 10 to 20 gallons per sprayed acre (GPA) with a range 5-40 GPA; read label for specifics.
(6) Do not apply herbicides when pine seedlings and desirable grasses are under drought or other stress
(7) Do not apply herbicides when rainfall is expected within one hour.
ENVOY® PLUS (Valent; 12.6% clethodim, 0.97 lb clethodim per gallon, contains petroleum distillates)
♦ Apply 9 to 16 fluid oz per acre for annual grasses, 12 to 32 oz/acre for perennial grasses
♦ Add crop oil concentrate which contains at least 15% emulsifier at 1% volume/volume (1 qt per 25 gallons spray solution, but no less than 1 pint per acre) or non-ionic surfactant at 0.25% volume/volume (1 qt per 100 gallons)
♦ Apply in 10 to 40 gallons of water per acre
♦ Do not apply more than 64 oz/ac/ per season, make a minimum 14 day interval between applications, do not apply more than 32 oz/ac per application
FUSILADE® DX (Syngenta; 24.5% fluazifop-P-butyl, 2 lb per gallon fluazifop-P-butyl)
♦ Apply 16-24 fluid oz product per acre per application
♦ Use a lower dose for annual grasses, a higher dose for perennial grasses
♦ Add 1% crop oil concentrate (1quart per 25 gal) or 0.25% nonionic surfactant (1 quart per100 gal)
♦ Do not apply more than 72 fluid oz Fusilade DX per acre, per season
ARROW® 2EC (Makhteshim Agan of North America (MANA); 26.4% clethodim, 2.0 lbs
clethodim per gallon, contains petroleum distillates)
♦ Apply 6 to 8 fluid oz product per acre for annual grasses and 8 to 16 oz/acre for perennial grasses
♦ Add crop oil concentrate which contains at least 15% emulsifier at 1% volume/volume (1 qt per 25 gallons spray solution, but no less than 1 pint per acre) or non-ionic surfactant at 0.25% volume/volume (1 qt per 100 gallons)
WEED TOLERANCE TO SELECTED HERBICIDES
| Herbicide | Weeds |
| ARSENAL | sicklepod, tropic croton, blackberry, most legumes |
| ARROW 2EC, ENVOY Plus | All broadleaf weeds |
| FUSILADE DX | All broadleaf weeds |
| OUST | bermudagrass, croton, Johnsongrass, trumpetcreeper, broomsedge |
| VELPAR | bermudagrass, broomsedge, cocklebur, Johnsongrass, sicklepod, trumpetcreeper, morningglory |
GRASS WEED RESPONSE TO HERBICIDES
| WEED | aFluazifop-P-butyl | bClethodim |
| Perennial Grassesbermudagrass | G – E | G – E |
| Bahiagrass | G | |
| Johnsongrass (rhizome) | E | E |
| tall fescue | F | |
| nutsedge | P | P |
| Annual Grassesbroadleaf signalgrass | E | E |
| crowfootgrass | F | G |
| crabgrass | F | G |
| fall panicum | G | G |
| goosegrass | F – G | F – G |
| Johnsongrass (seedling) | G – E | E |
| sandbur | G | G – E |
| Texas panicum | G – E | G |
E=Excellent (>90% control); G=Good(80-89% control); F=Fair(70-79% control); P=Poor(<70%). Citations: Guillebeau, P. (ed). 2005 & 2008. Georgia Pest Mgmt. Handbook. Special Bulletin 28. UGA Coop. Ext. Service. Athens, GA 30602. pp. 112, 156-57, 198-99. aFluazifop-P-butyl rating based on Fusilade DX trials, bClethodim ratings based on Select® and Arrow® trials.
Citation: Minogue, P. D.J. Moorhead, and E.D. Dickens. 2013 (Revised). Herbaceous weed control for planted longleaf sites. www.forestproductivity.net 7 p.
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