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Weeds - 239-Weed Control Guide for Wild Blueberries

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239-Weed Control Guide for Wild Blueberries 

Fact Sheet No. 239, UMaine Extension No. 2025 

Prepared by David E. Yarborough, Extension Blueberry Specialist, and Jennifer L. Cote, Research Assistant, The University of Maine, Orono, ME 04469. Revised January 2014.

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 use inconsistent with the label.

This fact sheet is to be used only during 2014. Use in subsequent years may lead to improper and illegal use of pesticides. When this guide is outdated, please request an updated version from your Extension office or on the web at: http://extension.umaine.edu/blueberries

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.

Groundwater is a major natural resource. Pesticides have been detected in the groundwater of all states. A sound application program including site-specific selection, adherence to label directions, sprayer calibration mixing accuracy, spill and back-siphon prevention, proper waste disposal, integrated pest management and judicious pesticide use can prevent groundwater contamination.

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.

Weed Management

The primary goal of weed management is to optimize yield by minimizing weed competition. Weeds reduce yields by competing with the crop for water, light and nutrients. No one method or chemical will control all weeds; each tends to reduce some weeds while encouraging others. Therefore, a combination of cultural techniques, the wise use of herbicides and careful monitoring of the weed situation in a field forms the basis of a sound weed management program.

Do not expect chemicals to completely control all weeds. The selection of herbicides should be made on the basis of what specific weed species are present in the field.

For additional information on the use of pesticides and other methods of weed control, refer to Wild Blueberry fact sheets entitled Weed Management in Wild Blueberry Fields (No. 236), Glyphosate for Weed Control in Wild Blueberries (No. 237), Hexazinone for Weed Control in Wild Blueberries (No. 238), Postemergence Grass Control for Wild Blueberries (No. 235), Tribenuron Methyl for Bunchberry Control in Wild Blueberries (No. 255), and Mesotrione Use in Wild Blueberries (No. 256). For detailed information on granular calibration refer to Calibration of Granular Applicators for Herbicide Impregnated Fertilizer Applications (No. 234). When using Velpar, review Hexazinone Best Management System for Wild Blueberry Fields (No. 250) for use precautions that will minimize leaching into groundwater. These publications can be found in the Wild Blueberry Growers Guide on CD, at your county Cooperative Extension office, from the Wild Blueberry Office at the University of Maine in Orono, or on the web at: http://extension.umaine.edu/blueberries

Preemergence herbicide rates are based on the amount of commercial product per acre or the percent solution for spot treatment. To achieve good weed control application equipment must be calibrated so that the required amount is applied accurately and uniformly. Under application may result in poor weed control. Over application can cause severe crop injury.

Postemergence non selective herbicides listed for herbaceous weeds and some herbicides for woody weeds applied to weed foliage with wiper or roller applicators and selective postemergence herbicides should be applied at the proper stage of weed growth.

Postemergence grass herbicides may be applied as a broadcast spray when grasses are small without injury to blueberries but are more effective as a spot treatment.

Cultural Weed Control Methods for Wild Blueberries

Weeds Controlled Method Comments
Most weeds, especially grasses Test soil for pH and adjust with sulfur if above 4.0. Add nitrogen or phosphorus fertilizer only if leaf analysis indicates a deficiency. Maintain soil pH at 4.0.
Most weeds except grasses Hand pulling Effective against spot infestations. Pull before any weed flowers go to seed.
Weeds spread by seed or vegetative parts carried on equipment, especially mechanical harvesters Field sanitation Steam clean and inspect equipment before entering a field.
Bracken fern, sweetfern, dogbane, seedling or sprouting trees, flowering weeds Mowing above blueberry plants Most successful if done during the vegetative year. Cut flowers off before they go to seed.
Coniferous trees, some weeds spread by seed Fire pruning When burning with straw or hay, use weed-free material.
Weeds that form crowns at or above ground level Flail-mow pruning Mow plants to ground level.
Some weeds spread by seed Mulching and/or planting blueberries on bare spots Apply mulch 2″ to 4″ deep. Use one of the following: bark, woodchips, shavings, sawdust, peat or sand.

 

THIS FACT SHEET IS INTENDED AS A GUIDE

Refer to the product label for details regarding soil type, soil moisture, temperature, stage of weed
growth and product limitations.

Chemical Weed Control Methods for Wild Blueberries Preemergence Weed Control

Problem Material Rate Product/a Comments & Limitations
Annual and perennial weeds Hexazinone
(Velpar L liquid 2 lbs active/gal)
4 to 12 pts. Do not exceed 8 pts. if treated with Hexazinone within past 8 years. Apply in spring after pruning in nonbearing year before blueberries emerge. Use lower rates on poorly drained soils and steep slopes. Moisture is required to activate; most effective in high temps/humidity. Avoid contact with blueberries. May be impregnated on fertilizer and applied after emergence up to tip-dieback. See 2ee label. Maintain a 50 foot buffer from any well head or water reservoir and do not apply to flooded fields.

450 day PHI

(Velpar DF 75% active) 1.2 to 3.6 lbs. Do not exceed 2.4 lbs per acre per season if treated with Hexazinone within past 8 years.
(Velossa 2.4 lbs. active/gal.) 3.3 to 10 pts. Do not exceed 6.6 pts. per acre per season if treated with Hexazinone within past 8 years.
Annual and perennial weeds Mesotrione
(Callisto liquid 4 lbs. active/gal.)
Non-bearing year:6 oz. preemergence

or

Bearing year: 4 oz/a prebloom (24C label)

Apply preemergence before blueberries emerge.

Do not exceed 6 fl oz. per acre per season in non-bearing year; or 4 fl oz. per acre per season in bearing year.

May be applied in the bearing year pre bloom to crop up to 60 days before harvest with State 24C label.

Grasses only Terbacil
(Sinbar 80 WP and WDG 80% active)
2 to 3 lbs.
Minimum 20 gpa water
Apply nonbearing year in spring after pruning or in crop year before bud-break. Do not use on soils with less than 1% organic matter, in sand or loamy sand with
Annual and perennial weeds Diuron
(Karmex XP/DF 80% active)
2 lbs. Apply nonbearing year only in late spring after pruning or in crop year before bud-break. Do not use on soils with
(Direx 4L, Diuron 4L liquid 4 lbs. active/gal) 1.6 qts. Moisture is required to activate Karmex.
Resistant grasses and herbaceous broadleaf weed Pronamide
(Kerb SC 3.3 lbs active/gal)
2.5 to 5 pts. Apply in a single application in late fall/early winter before soil freezes or snow. Most effective in soils with

May only be applied during the fall or winter of either year.

(Kerb 50W 50% active) 2 to 4 lbs.

Do not apply more than 5 pts. or 4 lbs. per acre per season.

Resistant grasses and herbaceous broadleaf weed Rimsulfuron(Matrix SG)

See supplemental label

2- 4 oz./yr. Apply in prune year only, pre-emergence broadcast or early post-emergence directed spray. Post-emergence spray or prolonged cold and/or wet weather may result in temporary chlorosis or stunting. Do not use on frozen/snow covered soil, soils classified as Sand or pre-emergence on soils with >6% OM. Spray solution should be pH 5-7 for best results.

Chemical Weed Control Methods for Wild Blueberries Postemergence Weed Control

Problem Material Rate Product/a Comments & Limitations
Broadleaf, herbaceous and woody perennial weeds Glyphosate
(use rate based on 41% glyphosate)

(Roundup and Touchdown formulations will vary in percentage of glyphosate — adjust use rates accordingly)
Wiper: Sponge – herbaceous 10% v/v, woody 20% v/v.Rope/wick – 33% v/v ordirected spray: 2% v/v.

Add 8.5 lbs. per 100 gallons ammonium sulfate to increase effectiveness on woody weeds only.

Avoid contact with blueberries. Will kill nearly all actively growing plants. Apply with wiper (10 to 33% solution) or as directed spray (2% solution). See labels for surfactant guidelines; do not use surfactant for wiper applications. Do not apply more than 6 lbs. acid equivalent for all formulations per acre per season. Do not apply within 14 days of harvest.
Grasses only Sethoxydim
(Poast liquid 1.5 lbs active/gal)
Spot application: 2 fl. oz. in 1 gal. water plus 1.5 fl. oz. crop oil concentrate or0.5 fl. oz. surfactant/gal.

Broadcast: 1.5 pt/a to 2.5 pt/a plus 2 pt/a COC.

Grass control only. Must add crop oil concentrate (COC) or surfactant.Do not apply when grass is drought-stressed. Do not apply more than 5 pts. per acre per season. Do not apply within 30 days of harvest.
Grasses only Fluazifop-P butyl
(Fusilade DX liquid 2 lb. active/gal.)
Spot application: 0.75 fl. oz. in 1 gal. water plus 1.5 fl. oz. crop oil concentrate or0.5 fl. oz. surfactant/gal.

Broadcast: 1-1.5 pt/a plus 2 pt. COC/25 gal. water or 1/2 pt. surfactant/25 gal. water.

Grass control only. Must add crop oil concentrate or surfactant. Do not apply when grass is drought-stressed. Do not apply if rainfall is expected within 1 hour. Use of other herbicide within 5 days may cause crop injury/reduced control.

Do not apply more than 72 fl oz. per acre per season.

May only be applied in the on-bearing year.

Grasses only Clethodim
(Select 2 EC liquid 2 lb. active/gal)

(Arrow 2 EC liquid 2 lb. active/gal)

(Clethodim 2 EX, Intensity, Section 2 EC, Shadow liquid 2 lb. active/gal)

Spot application: Mix 0.32 to 0.64 fl. oz. in 1 gal water plus0.5 fl. oz. surfactant.

Broadcast: 6 to 8 fl. oz/a plus 0.25% v/v surfactant in 5 to 40 gal/a water.

Grass control only. Apply as broadcast spray minimum 30 psi. Spot application, treat to wet but do not allow runoff. Must add surfactant. Crop oil concentrate not recommended. Multiple applications must be at least 14 days apart. Do not apply when grass is drought-stressed. Use higher rates for perennial grasses.

Do not apply more than 32 fl oz per acre per season.

May only be applied in the non-bearing year.

Grasses only (Select Max liquid 0.97 lb active/gal) Spot application: 0.44 to 0.85 oz. in 1 gal. water plus0.33 oz. surfactant.

Broadcast: annuals 9 to 16 oz/a, perennials 12 to 16 oz/a plus NIS at 0.25% v/v in 5-40 gal water.

See comments above.

Do not apply more than 64 fl oz. per acre per season.

May only be applied in the non-bearing year.

Bracken Fern only Asulam
(Asulox 24C label liquid 3.34 lbs. active/gal)
1 gal.

Use of non-ionic surfactant at 0.25% v/v may improve uptake of the Asulox.

For bracken fern control; bracken should be in full frond prior to application. Use Asulox only as a spot treatment. Do not apply more than once every other year.Control will be observed the year following application of the Asulox. No visible control symptoms will be observed the year of application.

Do not apply more than 1 gal. per acre per season.

May only be applied in the non-bearing year; see 24C label.

Bunchberry only Tribenuron methyl (Express TotalSol 50% active) 0.8 to 1 oz.

Use non-ionic surfactant at 0.25% v/v.

Apply in fall after blueberry harvest, up until killing frost. Do not use COC or methylated seed oil (MSO). Do not use in solutions below pH 6.0.

Do not apply more than 1 oz. per acre per season.

May only be applied after harvest and before pruning; see 24C label.

Annual and perennial weeds Mesotrione (Callisto liquid 4 lbs active/gal) Non-bearing year:3 oz. postemergence. Add crop oil concentrate at 1% v/v postemergence only.

Add 8.5 lbs. per 100 gals. ammonium sulfate to increase postemergence effectiveness.

Apply postemergence after weeds emerge. May be applied two times with 14 days between applications.

Do not exceed 6 fl. oz. per acre per season in non-bearing year.


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.

© 2014

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