2026 Weed Management for Wild Blueberry

Prepared by Lily Calderwood, Extension Wild Blueberry Specialist, and Leala Machesney, Extension and Research Professional.
Published February 2026.

Download This Chart

2026 Weed Management for Wild Blueberry Chart (PDF for printing)

This revised version replaces all previous charts.

Questions about Weed Management?

Contact Lily Calderwood, Extension Wild Blueberry Specialist at lily.calderwood@maine.edu.

Cultural Weed Management

Cultural weed management increases yield and reduces pesticide exposure to off-target organisms such as bees.

Weeds compete with wild blueberries for:

  • Water
  • Light
  • Nutrients

No single method controls all weeds. A combination of proper weed identification, monitoring, cultural management, and careful herbicide use (only when necessary) forms the basis of a sound weed management program.

Cultural Management Methods

Weeds Managed: Most weeds, especially grasses.

  • Test soil regularly.
  • Maintain soil pH between 4.0–4.5.
  • Reduce pH with sulfur if above 4.0.
  • Apply fertilizer only if leaf analysis indicates deficiency.

Weeds Managed: Most weeds except grasses.

  • Effective for spot infestations.
  • Pull before weeds flower and produce seed.

Weeds Managed: Weeds spread by seed or vegetative parts on equipment.

  • Power wash or steam clean equipment before entering fields.
  • Inspect mechanical harvesters carefully.

Weeds Managed: Bracken fern, sweet fern, dogbane, seedling or sprouting trees.

  • Most effective during vegetative year.
  • Remove flowers before seed production.

Weeds Managed: Coniferous trees and some seed-spread weeds.

  • Use weed-free straw or hay.

Weeds Managed: Woody weeds forming crowns above ground.

  • Cut three times during the non-crop year.
  • Cut plants to ground level.

Weeds Managed: Seed-spread weeds in bare spots.

  • Apply mulch 2–4 inches deep.
  • Use softwood chips, shavings, sawdust, peat, or sand.

Chemical Weed Management

Important: This guide is not a substitute for reading and following pesticide labels. It is unlawful to use any pesticide inconsistently with its label. The user assumes all responsibility for misuse. Trade names are used for identification only. No endorsement is implied. Check with your processor regarding PHI restrictions or MRL restrictions for export sales.

Group 1 – Grasses

Active Ingredient: Clethodim
Signal Word: Caution
Crop Stage: Prune Year, Early Crop
Timing: Post-emergence

Rate:

  • Broadcast*: 4 to 8 oz
  • No non-ionic surfactant spot application: 0.33 to 0.65 oz /1 gal-water
  • NIS spot application: Add 0.33 oz/1 gal-water NIS
  • Maximum annual application: 32 oz (0.5 lb ai)
  • 8 oz per application (at least 14 days apart)
  • 4 applications per year

PHI: 45 days
REI: 24 hours
Aerial/Drone Application: Can be aerially applied.

Important Notes:

  • *Read label for rate, use higher rates for perennial grasses. 
  • Clethodim: add 0.25% v/v NIS in 5 to 40 GPA water.
  • Apply as broadcast spray minimum 30 psi. (all)
  • Spot Treatment: Treat until wet but do not allow runoff.
  • Caution: Tank mixing with certain post-emergence broadleaf herbicides may reduce grass control. Do not use if rainfall expected in 1 hour.

Human & Environmental Risk:

  • Extremely toxic to people
  • Moderately toxic to aquatic life
  • Clethodim 2E: Moderate eye toxicity.
  • Moderate persistence
  • Systemic

Active Ingredient: Clethodim
Signal Word: Caution
Crop Stage: Prune Year, Early Crop
Timing: Post-emergence

Rate:

  • Broadcast*: annual 9 to 16 oz, perennial 12 to 16 oz.
  • Spot**: 0.44 to 0.85 oz /1 gal-water. 
  • Maximum: 64 oz (0.485 lb ai); 16 oz per application (at least 14 days apart), 4 applications per year.

PHI: 45 days
REI: 24 hours
Aerial/Drone Application: Can be aerially applied.

Important Notes:

  • *Add NIS 0.25% v/v in 5-40 GPA water.
  • **Add NIS at 0.33 oz/gal water.
  • Spot Treatment: Treat until wet but do not allow runoff.
  • Do not apply when grass is stressed.
  • Do not apply post-emergence broadleaf herbicides within 1 day of application.
  • Do not use if rainfall expected in 1 hour.

Human & Environmental Risk:

  • Extremely toxic to people
  • Moderately toxic to aquatic life
  • Moderate persistence
  • Systemic
  • High toxicity for aspiration, skin, mutagenicity and carcinogenicity.

Active Ingredient: Fluazifop-P butyl
Signal Word: Caution
Crop Stage: Prune year, Crop Year: Post-harvest
Timing: Post-emergence

Rate:

  • Broadcast*: 8 to 24 oz
  • Spot*: 0.75 oz./1 gal-water
  • Maximum: 2 app of 24 oz/application (at least 14 days apart); Total 48 oz (0.75 lb ai)

PHI: 305 days
REI: 12 hours
Aerial/Drone Application: Can be aerially applied.

Important Notes:

  • *Add 0.25-0.5% v/v NIS or 0.5-1% v/v COC in 5-40 GPA water.
  • Application: Apply in the interspaces and around the base of plants while avoiding contact of spray with plants.
  • Do not use if grass is drought-stressed or if rainfall is expected within one hour.
  • Crop injury may occur if other herbicides are applied within 5 days, also reducing control efficacy.

Human & Environmental Risk:

  • Extremely toxic to people
  • Extremely toxic to aquatic life
  • High aspiration toxicity
  • Moderate persistence
  • Systemic

Active Ingredient: Sethoxydim
Signal Word: Warning
Crop Stage: Prune Year, Early Crop
Timing: Post-emergence

Rate:

  • Broadcast*: 1.0 to 2.5 pints
  • Spot**: 1.3 oz (1.0%) or 1.9 oz (1.5%) and 1.3 oz COC/MSO in 1 gal water
  • Maximum: 5 pints; 2 applications per year of 2.5 pints per application (at least 14 days apart).

PHI: 30 days
REI: 12 hours
Aerial/Drone Application: Can be aerially applied.

Important Notes:

  • *Add 2 pints/acre COC in 5 to 20 gallons water per acre.
  • Minimum 40 PSI.
  • **Add 1.3 oz COC/1 gal water.
  • Must add crop oil concentrate (COC) or surfactant.
  • Do not apply when grass is drought stressed.

Human & Environmental Risk:

  • Extremely toxic to people
  • Extremely toxic to aquatic life
  • High aspiration toxicity
  • Moderate persistence
  • Systemic

Group 2 – Broadleaf, Grasses & Sedges

Active Ingredient: Halosulfuron-methyl
Signal Word: Caution
Crop Stage: Prune Year
Timing: Pre-emergence

Rate:

  • 0.5 oz to 1 oz per acre
  • Maximum: 1 oz (0.047 lb a.i) per year

PHI: 14 days
REI: 12 hours
Aerial/Drone Application: Not permitted.

Important Notes:

  • Apply in minimum 20 gallons water per acre. Do not apply by rope-wick wiper.
  • Applications should be made 1 to 2 months prior to breaking dormancy in the spring.
  • Phytotoxicity may occur with overlapping boom swaths (overapplication).
  • Do not apply when frost is present or where soil is saturated.
  • Do not apply to water saturated soils.
  • Do not apply to areas where water is known to pond for periods of time following rainfall.
  • Do not apply to plants that have progressed into budbreak.
  • Do not apply to plants under stress or less than one year of age.

Human & Environmental Risk:

  • Extremely toxic to aquatic life
  • Low persistence
  • Systemic

Active Ingredient: Tribenuron-methyl
Signal Word: Caution
Crop Stage: Prune Year, Crop Year: Post-Harvest
Timing: Post-emergence

Rate:

  • 1 oz per acre
  • Spot*: 1 oz/20 gal water
  • Add NIS 0.25% v/v
  • Maximum: 1 oz per acre/yr

PHI: 365 days
REI: 12 hours
Aerial/Drone Application: Not permitted.

Important Notes:

  • *Add NIS at label rate.
  • Spot Treatment: apply during summer of prune year.
  • For special use on bunchberry. 
  • Apply in the spring of a prune year or fall after harvesting and up until killing frost.
  • Fertilizer applications before or after applying Express will help blueberry plants recover.
  • Do not use COC or an MSO.
  • Do not use in solutions below pH 6.0.
  • Do not apply to drought-stressed plants.
  • Prolonged cool temps (<50F) or wide fluctuations in day-night temps around time of treatment may cause temporary crop yellowing or stunting.
  • Do not apply within 365 days of blueberry harvest.

Human & Environmental Risk:

  • Moderately toxic to people
  • Moderate skin toxicity
  • Moderate persistence
  • Systemic

Group 3 – Resistant Grasses

Active Ingredient: Pronamide
Signal Word: Caution
Crop Stage: Crop Year: Post-Harvest
Timing: Pre-Emergence, Post-Emergence

Rate:

  • 2.5 to 5 pints per acre
  • Maximum: 1 application of 5 pt (2 lbs. per ai) per year

PHI: No specific PHI listed for lowbush blueberry (ranges 25–60 days depending on crop)
REI: 24 hours
Aerial/Drone Application: Can be aerially applied.

Important Notes:

  • May only be applied in fall/winter of either year (before ground-freeze or snow). 
  • Rate depends on the weed species present (see label).
  • Mix specified amount into 20 to 50 GPA of water and apply at a low pressure.
  • Field Conditions: Most effective in soil with <4% organic matter and when temperature is <55°F. 
  • Activation: Rain/snowmelt is required to move into root zone.

Human & Environmental Risk:

  • Extremely toxic to aquatic life
  • Acute inhalation toxicity
  • Moderate carcinogenicity
  • High persistence
  • Systemic

Group 5 – Grass and Broadleaf

Active Ingredient: Hexazinone
Signal Word: Danger
Crop Stage: Prune Year
Timing: Pre-Emergence

Rate:

  • 1.2–3.6 lbs., minimum 20 gallons per acre
  • Maximum: 2.4 lbs. if applied in previous 8 years

PHI: 450 days
REI: 48 hours
Aerial/Drone Application: Can be aerially applied.

Important Notes:

  • Apply in spring of prune year, pre-emergence.
  • Only apply once per year. 
  • May be impregnated on fertilizer.
  • Use lower rates on poorly drained soil and steep slopes.
  • Use higher rates on heavier soil or soils high in organic matter. 
  • Activation: Moisture required within 2 weeks of treatment; high temps and humidity help. 
  • Caution: Maintain a 50-foot buffer from any well head or water reservoir and do not apply to frozen or flooded fields.
  • Do not apply through an irrigation system.
  • Avoid contact with blueberry plants. 

Human & Environmental Risk:

  • Extremely toxic to people
  • Highly toxic to eyes
  • High persistence
  • Systemic

Active Ingredient: Terbacil
Signal Word: Caution
Crop Stage: Prune Year, Crop Year: Post-Harvest
Timing: Pre-emergence

Rate:

  • 2–3 lbs. per acre, minimum 20 gallons per acre
  • Maximum 3 lbs. per year

PHI: No specific PHI listed for lowbush blueberry, only PHI listed is for watermelon which is 70 days.
REI: 12 hours
Aerial/Drone Application: Not permitted.

Important Notes:

  • Apply pre-emergence in prune year or in crop year after harvest. 
  • Use higher rate on heavy soil or soils high in organic matter.
  • May be impregnated on fertilizer (See 2ee label). 
  • Activation: Moisture required. 
  • Do not use on soil with <1 % organic matter, in sand or loamy sand with <3% OM, or where roots are exposed.
  • Avoid contact with blueberry plants.

Human & Environmental Risk:

  • Extremely toxic to aquatic life
  • High persistence
  • Systemic

Group 7 – Grass and Broadleaf

Active Ingredient: Diuron
Signal Word: Caution
Crop Stage: Prune Year
Timing: Pre-Emergence

Rate:

  • 1.6 quarts per acre

PHI: Not applicable
REI: 12 hours
Aerial/Drone Application: Can be aerially applied.

Important Notes:

  • Apply in late spring of prune year pre-emergence.
  • Activation: Moisture required within 2 weeks of treatment.
  • Caution: Do not use on soils with <2% organic matter or on foliage or exposed roots.
  • Do not use near fruit trees.

Human & Environmental Risk:

  • Moderately toxic to people
  • Extremely toxic to aquatic life
  • Acute oral toxicity
  • High persistence
  • Systemic

Group 9 – Resistant Grass and Broadleaf

Active Ingredient: Glyphosate
Signal Word: Caution
Crop Stage: Prune Year, Crop Year
Timing: Post-emergence

Rate:

  • Wiper: Sponge 10% v/v herb, 20% woody; Rope/wick-33% v/v.  
  • Directed spray:  2% v/v
  • Maximum: 6 lb a.e. for all formulations (see label)

PHI: 14 days
REI: 4 hours
Aerial/Drone Application: Depends on formulation, refer to the label.

Important Notes:

  • Use rate based on 41-49%, adjust accordingly.
  • Add 1- 2% w/w spray grade AMS to increase efficacy on woody weeds only.
  • See labels for surfactant guidelines; do not use surfactant for wiper applications. 
  • Caution: non-selective: will kill all actively growing plants.
  • Avoid contact with blueberries.

Human & Environmental Risk:

  • Moderately toxic to aquatic life
  • Low persistence
  • Systemic

Active Ingredient: Rimsulfuron
Signal Word: Caution
Crop Stage: Prune Year
Timing: Pre-Emergence or Early Post-Emergence

Rate:

  • 4 oz/acre
  • Maximum: 1 application of 4 oz per year (0.0625 lb ai)
  • For spray: use NIS 0.125-0.25% v/v or COC 1% v/v
  • Matrix: most effective at spray tank solution pH of 5 to 7; maximum 1 broadcast per year or 2 band applications per year.

PHI: 21 days
REI: 4 hours
Aerial/Drone Application: Can be aerially applied.

Important Notes:

  • Pre-emergence: Broadcast before bud break. 
  • Early post-emergence: Directed spray while avoiding contact with blueberry plants. 
  • Do not use on soils with >6% organic matter.
  • Solida: Rainfall or irrigation needed within 2 weeks of application to activate herbicide in the soil, most effective within 5 to 7 days.
  • Post-emergence spray may result in temporary chlorosis or stunting.
  • Do not use on frozen/snow covered soil or soils classified as sand.

Human & Environmental Risk:

  • Extremely toxic to aquatic life
  • Low persistence
  • Systemic

Group 10 – Resistant Grass and Broadleaf

Active Ingredient: Glufosinate-ammonium
Signal Word: Warning
Crop Stage: Prune Year
Timing: Post-Emergence

Rate:

  • Broadcast: 48 oz/acre
  • Spot: 1.7 oz in 1 gal water
  • Maximum: 164 oz (3 lbs. ai)per year; 2 applications of 82 oz per application

PHI: 14 days
REI: 12 hours
Aerial/Drone Application: Can be aerially applied.

Important Notes:

  • Foliar-active only.
  • Apply pre-blueberry emergence.
  • Field Conditions: Apply on a warm, sunny humid day.
  • Add to spray tank last; may require an antifoam agent.
  • Do not apply to blueberry plants.
  • Do not apply through irrigation system.

Human & Environmental Risk:

  • Extremely toxic to people
  • Highly toxic to skin and reproductive system
  • Low persistence
  • Systemic

Group 14 – Resistant Grass and Broadleaf

Active Ingredient: Sulfentrazone
Signal Word: Caution
Crop Stage: Prune Year
Timing: Pre-Emergence

Rate:

  • Broadcast: 4 to 12 fl . oz. per acre (0.13 to 0.38 lb ai/A), minimum 10 gallons per acre
  • Maximum: 12 fl oz (0.38 lb. a.i.) per acre per year
  • Maintain spray solution between pH 5-9.

PHI: 3 days
REI: 12 hours
Aerial/Drone Application: Can be aerially applied.

Important Notes:

  • Apply in prune year before blueberry emergence. 
  • Availability decreases with finer soils and increases with higher pH; do not apply on sand with <1% OM. 
  • Activation: apply to moist soil with o.5 to 1 inch of rainfall/irrigation within 2 weeks of application. 
  • Caution: do not tank mix with flumioxazin or other products containing sulfentrazone. 

Human & Environmental Risk:

  • Moderately toxic to people
  • Moderately toxic to aquatic life
  • Moderate liver toxicity
  • Carcinogenicity risk
  • Moderate persistence
  • Systemic

Group 18 – Fern

Active Ingredient: Asulam
Signal Word: Caution
Crop Stage: Prune Year
Timing: Post-Emergence

Rate:

  • Spot application only* 
  • Add NIS 0.25% v/v
  • Maximum: 1 gal per acre.
  • Apply every other year.

PHI: 365 days
REI: 12 hours
Aerial/Drone Application: Not permitted.

Important Notes:

  • For special use on bracken fern in the prune year. 
  • Field Conditions: Ferns should be in full frond.
  • Apply once every other year on prune-field only; control symptoms will not be visible until the following year. 

Human & Environmental Risk:

  • Extremely toxic to people
  • Extremely toxic to aquatic life
  • High toxicity to skin and eyes
  • Moderate persistence
  • Systemic

Group 27 – Annual Broadleaf

Active Ingredient: Mesotrione
Signal Word: Caution
Crop Stage: Prune Year, Early Crop Year
Timing: Pre-Emergence and Post-Emergence

Rate:

Prune Year:

  • 2 oz (24c label)
  • Maximum: 2-3 applications of 2 oz (minimum 14 days apart) or 1, 6 oz (0.19 lb ai/A) application.

Early in Crop Year:

  • 4 oz. (24c label) Add NIS 0.25% v/v
  • Maximum: 1 application of 4 oz (0.19 lb ai) per year.

PHI: 60 day
REI: 12 hours
Aerial/Drone Application: Not permitted.

Important Notes:

  • Post-emergence applications must be made before weeds reach 5 inches in height.
  • Application must be made prior to bloom.
  • Do not apply by air for prune or early crop stage.
  • To increase efficacy: Add COC (1% v/v). Add 8.5 lbs AMS/100-gal water.
  • Crop Injury may occur in dry conditions or over 85°F.
  • See 24C label for revised prune year/crop year application.

Human & Environmental Risk:

  • Moderately toxic to people
  • Avoid repeated exposure
  • Moderate persistence
  • Systemic

Active Ingredient: Mesotrione
Signal Word: Caution
Crop Stage: Prune Year
Timing: Pre-Emergence and Post-Emergence

Rate:

  • 3 to 6 oz
  • Maximum: 2 applications of 3 oz per year (minimum 14 days apart) or 1 application of 6 oz per year

PHI: Not available
REI: 12 hours
Aerial/Drone Application: Not permitted.

Important Notes:

  • Post-emergence applications must be made before weeds reach 5 inches in height.
  • Application must be made prior to bloom.
  • Do not apply by air for prune or early crop stage.
  • To increase efficacy: Add COC (1% v/v). Add 8.5 lbs AMS/100-gal water.
  • Crop Injury may occur in dry conditions or over 85°F.

Human & Environmental Risk:

  • Moderately toxic to people
  • Avoid repeated exposure
  • Moderate persistence
  • Systemic

Footnotes

Environmental Persistence Rankings

Environmental persistence rankings were estimated using a combination of soil and hydrologic persistence, PHI, and REI.

Group Number

To reduce the likelihood of herbicide resistance developing in target weeds, growers should rotate between herbicides with different group numbers in the growing season, ideally using multiple group numbers. Products with the same group number should not be used in consecutive sprays.   

Information in these publications 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.