235-Postemergence Grass Control for Wild Blueberries

Fact Sheet No. 235, UMaine Extension No. 2148

Prepared by David E. Yarborough, Extension Blueberry Specialist, The University of Maine, Orono ME 04469.  February 1999.

NOTICE: It is unlawful to use any pesticide for other than the registered use. Read and follow the label on the product container. The user assumes all responsibility for a use inconsistent with the label.

WARNING! Pesticides are potentially hazardous. Handle carefully! Read and follow all directions and precautions on labels. Store in original labeled containers out of reach of children, pets, and livestock. Dispose of empty containers at once, in a safe manner and place. Do not contaminate forage, streams, ponds or groundwater recharge areas.

Trade names are used for identification. No product endorsement is implied, nor is discrimination intended against similar materials. Cooperative Extension makes no warranty or guarantee of any kind concerning the use of these products.


Poast®, the trade name for sethoxydim; Fusilade®, the trade name for fluazifop-P-butyl; and Select ®, the trade name for clethodim are selective post-emergence herbicides that may be used to suppress grasses not adequately controlled by pre-emergence applications. Combined with a crop oil concentrate or a nonionic surfactant, they will suppress many annual and perennial grasses but will not control other herbaceous or woody broadleaf weeds nor injure wild blueberries. These herbicides may be applied as a broadcast spray, but spot treatments are more effective. Application of Fusilade® and Select ® may be made only in the nonbearing year. Applications of Poast® may be made up to thirty days before a crop is harvested.

Growth of treated grass weeds stops shortly after application. Symptoms include loss of vigor, yellowing or reddening, burnback and eventual death to the treated grass plant. Symptoms are generally observed within one to three weeks, depending on the grass weed species and the temperature and rainfall. If green grass growth resumes or more seedlings emerge within two weeks, it will be necessary to treat again.

Application Directions

Use for grasses not controlled by Velpar®, Pronone® or Sinbar®, or to control grasses to which pre-emergence herbicides were not applied. Only annual and perennial grass weeds are susceptible to Poast®, Fusilade® or Select®. Many grass species will occur in wild blueberry fields. Examples of those requiring additional control include annual grasses such as witchgrass, fall panicum or fools hay. Perennial grasses needing additional control include bunch-grass or little bluestem, and quackgrass. Refer to the Weed ID tool for grass identification.

Other grass-like weeds, such as rushes or sedges, will not be controlled by these herbicides.

Timing: Growth Stage Very Important

  • Apply to actively growing grasses from two to eight inches in height.
  • Applications made when grasses are short (two to four inches) will result in better control, and will be less likely to require a second treatment.
  • Perennial grasses will require multiple treatments for lasting suppression.
  • Do not apply once the grass has gone to seed.
  • Do not apply if rain is expected within one hour.
  • Do not apply to grass that is stressed due to moisture, temperature, low soil fertility, or mechanical or chemical injury.

Add Surfactants

Always add one of the following:

  • Crop oil concentrate (COC): non-phytotoxic crop oil concentrate at one percent (one quart per 25 gallons) of the finished spray volume


  • Nonionic surfactant at 0.25 percent (1/2 pint per 25 gallons) of the finished spray volume.

Broadcast Recommendations

Fusilade DX®: 0.75 pt/A with COC at one percent or nonionic surfactant at 0.25 percent of finished spray volume in 5 to 30 gal./A water at 40-60 psi pressure. Fusilade DX®: 0.75 pt./A with COC at one percent or nonionic surfactant at 0.25 percent of finished spray volume in 5 to 30 gal./A water at 40-60 psi pressure.

Poast®: 2.5 pt./A with 2 pt./A COC in 5 to 20 gal./A water at 40-60 psi pressure. Do not use a nonionic surfactant. Do not apply more than five pints per acre per season.

Select®: 6 to 8 Fl oz/A with 1% v/v COC/ or minimum of 1 pt./a in 5 to 40 gal./a water at 30 to 60 psi pressure. Minimum 3 gal. water/A by air.

Spot Spray Recommendations: Application to grass on a spray-to-wet basis
Spray Volume
Fusilade DX®
(fl. oz.)
(fl. oz.)
Crop Oil Concentrate
(fl. oz.)
Nonionic Surfactant
(fl. oz.)
1 0.75 2 0.64 1.5 0.5
10 6.50 20 6.4 13.0 3.0
25 16.00 30 16.0 32.0 8.0
1 tablespoon = 0.5 fl. oz.; 32 fl. oz. = 1 quart

Spray Marker: An approved dye or spray pattern indicator may be mixed in the tank to mark areas sprayed. Recommended dyes include Blazen Blue®, Spray Tracer® and Signal®.

Note: Be sure to clean sprayer thoroughly before using Poast®, Fusilade® or Select ® to prevent injury to blueberries from residual chemicals.  This fact sheet is only a guide. Always consult the label before using any pesticide.

Information in this publication is provided purely for educational purposes. No responsibility is assumed for any problems associated with the use of products or services mentioned. No endorsement of products or companies is intended, nor is criticism of unnamed products or companies implied.

© 1999

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