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Section 13: Herbicide Spraying Operations

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Overview

The purpose of the herbicide spraying operation is to control noxious and invasive plants that may cause a safety concern, compete with desirable vegetation on the right of way and are detrimental to the environment. An effective spraying program has been shown to reduce mowing cycles, mowing costs and to improve the overall condition of the highway system.

It is very important that application timing guidelines are followed to ensure that spraying operations do not affect the emergence and growth of wildflowers.

Herbicide spraying operations must be coordinated with mowing operations to be effective.

Please refer to Flex 5 Spray Unit (GSD Issue), Use of Roundup Pro + Outrider Combination for Johnson grass Control, and Application Timing for Approved Aquatic Herbicide.

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Bare ground Applications

Bare ground applications are herbicide treatments to the edge of pavement and vegetation encroachment within paved shoulders, retaining walls and paved and raised medians. The recommended application rate for these treatments is 4 quarts of Roundup Pro plus Landmark® XP at 2 ounces per acre to provide for short term control of edges and 3 ounces per acre of Landmark® XP for extended control of vegetation. These applications are generally made from March through September. The most effective applications to control bermudagrass are generally made later in the recommended spray schedule.

These applications should be restricted to no more than 6 inches from the edge of the paved surface and 12 inches behind the guardrail. Applications wider than 12 inches may result in erosion and soil sediment loss.

Reference: Bare Ground (or Complete) Vegetation Control, Mixing Drift Control Agents with Roundup Pro and Landmark XP, Bermuda grass, Roundup Pro for Complete Control in Riprap, Raised Medians, Paved Medians and Retaining Walls, General Characteristics of Landmark® XP (Replaces Oust XP).

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Guardrail Applications

The recommended herbicides and application rates are 8 ounces of Roundup Pro plus 1.33 ounces of Outrider® plus ½ ounce of Escort XP plus 10 ounces of Vista per acre. If Vista is not added to the mixture, the Escort XP rate should be raised to 1 ounce per acre. These applications are generally made from May through October.

Herbicide applications to control winter annuals (such as ryegrass, mustards and turnip weed) are recommended in the spring to improve visibility of guardrails. The application rate for these treatments is 16 ounces of Roundup Pro plus 2 ounces of Landmark XP per acre. These applications are made January through April.

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Noxious Weed Control

Broadcast herbicide applications are required to control noxious weeds on the right of way such as Johnsongrass, Switchgrass, Giant Ragweed, Sunflowers, Field Bindweed and other broadleaf weeds. The recommended herbicides and application rates are 8 ounces of Roundup Pro plus 1.33 ounces of Outrider plus ½ ounce of Escort XP plus 10 ounces of Vista per acre. If Vista is not added to the mixture, the Escort XP rate should be raised to 1 ounce per acre. These treatments are also recommended to treat guardrails, signs and delineators when grasses are desired around and under these structures. Applications are generally made from May through October; however, Escort XP should be discontinued after July 31.

Reference: Selective Weeding, Mixing Drift Control Agents with Roundup Pro, Escort XP and Outrider, Mixing Drift Control Agents with Roundup Pro and Outrider, Noxious Weeds and Pests on the Right of Way, Use of Roundup Pro + Outrider Combination for Johnson grass Control, Application Procedures with Escort XP, Application Procedures for Transline on Mesquite, Application Procedures for Vista on Giant Ragweed (Bloodweed)

Broadcast and spot applications of Transline in the spring (January through April) may be necessary to control Musk Thistle. Application rates are 10 ounces per acre applied as a broadcast application and 10 ounces per 100 gallons of water for spot treatments. Spot applications are recommended in areas where large populations of wildflowers exist.

Reference: Mixing Drift Control Agents with Transline, Application Procedures for Transline on Musk Thistle.

In some cases, it will be necessary to make herbicide applications with the handgun to noxious plants that cannot be sprayed with broadcast application equipment. To determine the proper herbicide application rate, find recommended rate per acre in this manual or in the manufacturer's chemical label. Add the recommended rate of the chemical to 100 gallons of water for handgun use. In many instances, surfactant is also recommended.

Reference: Approved Chemicals for Right of Way Vegetation Management.

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Brush and Tree Control

Low volume foliar and basal bark herbicide applications will be necessary to control brush and trees such as Mesquite, Huisache, Retama, and Kudzu on the right of way.

Low volume foliar treatments are made using a solution of 1/2% Transline plus 1/2% surfactant applied with a handgun equipped with an X-6 spray tip. The application should be made uniformly over the entire plant. These treatments are generally made in mid-summer through fall.

Reference: Mixing Drift Control Agents with Transline, Mesquite, Huisache, Retama, Kudzu, Application Procedures for Transline on Mesquite,Application Procedures for Transline on Huisache, Application Procedures for Transline on Retama, Application Procedures for Transline on Kudzu, Low Volume Foliar Spray for Transline on Mesquite and Huisache.

Basal bark herbicide applications can be made year-round using the ready-to-use herbicide, Pathfinder II. Apply Pathfinder II to the lower 12-15 inches of bark using an X-1 or X-2 spray tip.

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Aquatic Weed Control

Handgun herbicide applications are often necessary to control aquatic vegetation. Aquamaster applied at 8 quarts plus 2 quarts of an aquatically approved surfactant per 100 gallons of water is recommended to control undesirable vegetation growing in standing or running water.

Reference: Mixing Drift Control Agents with Approved Aquatic Herbicide, Approved Aquatic Herbicide.

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