Using Glufosinate for Weed Control in the Delta

What is glufosinate?

Glufosinate-ammonium is a glutamine synthetase inhibitor (Group 10), water-soluble nonselective herbicide for the control of many emerged broadleaf and grassy weeds. The glufosinate label MUST be followed.

What is the control mechanism of a Group 10 herbicide?

Group 10 herbicides block (inhibit) the activity of the enzyme glutamine synthetase, which is essential for converting ammonia to glutamine. The inhibition creates toxic ammonia levels which causes cell destruction and tissue death.¹

How should glufosinate be used for weed control?

Glufosinate must be foliar applied to actively growing broadleaf and grassy weeds. For labeled crops, it can be used as a burndown prior to planting and prior to crop emergence. It can also be used postemergence in labeled glufosinate-resistant crops. There is little or no soil activity; therefore, control is only obtained on emerged weeds that are thoroughly sprayed.

Are there environmental conditions that enhance glufosinate efficacy?

The glufosinate label indicates that activity and performance can be enhanced by warm temperatures, high humidity, and bright sunlight. Because sunlight is required for activity, applications should be made between sunrise and two hours before sunset.

Can efficacy be reduced by certain environmental conditions?

Efficacy may be reduced if an application is made when weeds are experiencing heavy dew, fog, mist, or rain. Additionally, weed control efficacy can be reduced when the weeds are under stress from drought, cool temperatures, or extended periods of cloud cover.

How long should glufosinate be in contact with foliage prior to rain?

For most weed species, glufosinate is rainfast four hours after application. If rain occurs within four hours, retreatment may be necessary as reduced weed control may result. Refer to label for reapplication restrictions.

Should cultivation be avoided?

Per the glufosinate label, DO NOT cultivate from five days before an application to seven days after an application.

What are the label recommendations for ground application?

For best results, glufosinate applications should be made to small weeds (less than three inches in height) and applied in a minimum of 15 gallons of water per acre (GPA). For large weeds, dense foliage, or when using larger spray droplets, GPA should be increased to 20 GPA. Mandatory spray drift mitigation MUST be practiced.

What are the label recommendations for aerial application?

Labeled aerial applications should occur when weeds are small (less than three inches in height) and applied using a minimum of 10 gallons of water per acre (GPA). Mandatory spray drift mitigation MUST be practiced.

What is the preferred droplet size?

A medium droplet size of about 300 microns is recommended.

What are the preferred nozzles for applying glufosinate?

Preferred nozzles include flat-fan, Turbo TeeJet^®, and TurboDrop^® Asymmetric DualFan Nozzle for Agriculture (TADF). Refer to glufosinate label for additional nozzle information.

Are any adjuvants recommended for improved weed control?

Ammonium sulfate (AMS) has shown improved control of difficult-to-control weeds when relative humidity is low or hard water is used in the tank. AMS rates (1.5 to 3.0 lb/acre) are dependent on tank mix partners, environmental conditions, temperatures, and potential for leaf burn. Additional surfactants are not needed as crop injury may occur; however, an antifoam agent is recommended.

Other observations?

• Follow glufosinate label for approved tank mix partners.
• Avoid four-way tank mixes such as a glyphosate + glufosinate + an acetochlor herbicide + an insecticide.
• Glufosinate + a Group 15 (shoot growth inhibitors) herbicide may cause injury to cotton.
• Glufosinate + insecticide tank mixes may enhance injury.
• Glufosinate performance may be improved with the addition of a graminicide.
• Thorough spray coverage is needed due to limited translocation.

Always follow all label instructions.

Sources

¹2023. Glutamine synthetase inhibitor (HG 10) herbicide injury to corn. Crop Protection Network. https://cropprotectionnetwork.org/encyclopedia/glutamine-synthetase-inhibitor-hg-10-herbicide-injury-in-corn

Web source verified 4/22/25. 1026_515250