MONSANTO │WEED MANAGEMENT SOLUTIONS

Preharvest applications of Roundup® brand agricultural herbicides can be used in declining alfalfa and other labeled forage legume stands where crop destruction is desirable. A preharvest application can control or suppress annual and perennial weeds, while helping to provide improved control of legumes and perennial grasses compared to an application after harvest. Late summer to early fall applications are generally considered the best time for the termination of declining alfalfa and forage crop stands.

Preharvest Application

Roundup agricultural herbicides (glyphosate) are registered as a preharvest treatment in alfalfa and other labeled forage legumes to eliminate or destroy declining crop stands being removed from the rotation. In alfalfa, up to 44 fluid ounces per acre of Roundup herbicide can be applied as a broadcast spray at least 36 hours before harvest. For other legumes listed, up to 32 fluid ounces per acre of Roundup herbicide can be applied at least 3 days before harvest (Table 1). Not all glyphosate products are registered for this application, and product labels should be checked for approved uses and recommendations.

Late Summer to Early Fall Treatment

Preharvest applications to alfalfa and other forages can be made any time of the year. However, late summer to early fall applications are generally considered best for control of perennial weeds and termination of forage crop stands.1 With late summer and fall applications, more downward translocation of Roundup herbicide to root buds and storage organs of perennial weeds, legumes, and grasses, can leave them unviable for the next season.

Treatment this time of year can also optimize the decomposition of existing root masses, including those of forage species and perennial weeds, helping to make seeding of a new crop easier next season.2

Crop Stand and Weed Removal

Forage fields at the time of termination should be at or near the normal stage of cutting. Perennial legumes, like alfalfa, should be in the bud to flower stage of growth at the time of application. Perennial grasses, like quackgrass, should have at least 3 to 4 leaves. Alfalfa and quackgrass should be allowed to re-grow to a height of 6 to 8 inches or more prior to treatment. Deep tillage following preharvest treatment may be required to provide complete control of well established perennials.

Kochia Management in Corn and Soybeans

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Preharvest Applications to Alfalfa and Other Forages

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Table 1. Maximum single preharvest application rate for

Roundup® brand agricultural herbicides, and the

minimum interval between application and harvest or

livestock grazing of the forage.

Rate per Acre Harvest Interval

Alfalfa 44 fluid ounces 36 hours

Other Legumes* 32 fluid ounces 3 days

* Includes clover, kudzu, lespedeza, lupin, sainfoin, trefoil,

velvet bean, and all types of vetch.

Declining alfalfa stand prior to the last cutting,

and to be removed from the crop rotation. A

late summer to early fall preharvest treatment

can provide better stand removal than a

treatment applied after harvest.

2 │ 2

from previous page

Individual results may varyIndividual results may varyIndividual results may varyIndividual results may vary, and performance may vary from location to location and from year to year. This result may not be an indicator of results you may obtain as local growing, soil and weather conditions may vary. Growers should evaluate data from multiple locations and years whenever possible. ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS.ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS.ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS.ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS. Roundup PowerMAX®, Roundup Ready PLUS™, Roundup WeatherMAX and Design®, Roundup®, Technology Development by Monsanto and Design®, and Transorb and Design® are trademarks of Monsanto

Technology LLC. ©2011 Monsanto Company. 07292011TED

MONSANTO │WEED MANAGEMENT SOLUTIONS

In no-till systems, effective termination of a forage stand may involve the control of volunteer alfalfa or other legumes, grasses, and problem weeds prior to seeding a rotation crop, along with an effective in-crop weed control program. If the field is planted to corn next season, including atrazine in the preplant/preemergence herbicide program can aid in control of perennial grasses. Postemergence applications of dicamba or 2,4-D may be required for complete control of alfalfa and broadleaf weeds in the corn.1,2

Harvest Timing

For effective control of the forage crop, wait at least 3 days after spraying before cutting hay or grazing pasture. Time is required to allow Roundup herbicide to translocate (move) into the root system for best control results. Depending on weather conditions, hay quality may be reduced if cut much later than 7 days after spraying.

Sources:

1Baig, M. N. and Gamache, P. 2007. No-till seeding of annual crops into alfalfa/grass forages. Alberta Reduced Tillage Linkages. April 2, 2007. http://www.reducedtillage.ca (verified 7/29/2011).

2Yoder, H. 2007. Removing forages from the rotation in a direct seeding system. Alberta Agriculture and Food. Agdex 519-17, revised November 2007. http://www1.agric.gov.ab.ca (verified 7/29/2011).

Preharvest Applications to Alfalfa and Other Forages

Preharvest Application GuidelinesPreharvest Application GuidelinesPreharvest Application GuidelinesPreharvest Application Guidelines ⇒ Make Roundup® brand agricultural herbicide

treatment at or near the normal stage of forage cutting.

⇒ Perennial legumes (like alfalfa) should be at the early bud to early bloom stage, and perennial grasses (like quackgrass) should have at least 3 to 4 leaves.

⇒ The highest application rate allowed should be used when a forage stand is dense and/or hard to control grasses are present.

⇒ Optimum harvest time is 3 to 7 days after application to maximize perennial weed control and maintain hay quality.

⇒ Treated forage can be fed to any livestock including lactating animals.

⇒ Do not use on forage crops being grown for seed, as a reduction in germination or vigor may occur.