Wild Blueberry Best Management Practices for Weeds

Wild Blueberry Best Management Practices for Weeds

1

Introduction

• David Yarborough

• Blueberry Specialist

• Professor of Horticulture

• University of Maine in Orono

• 1‐800‐897‐0757

• [email protected]

• www.wildblueberries.maine.edu

Wild Blueberry Weed BMP’s

David E. Yarborough - the University of Maine

2

Figure 1. Yield from Untreated Plots byInitail Weed Cover on Percent from All Years

0 25% 50% 75% 100%0

1

2

3

4

5

6

Fern 4.639 3.371 3.252 1.887 0.857

Dogbane 5.515 4.463 2.272 2.38 1.434

Treatment, Cover = Highly Significant

Weed Cover

Why Control Weeds?

Reduce Yield Reduce QualityReduce Value and price to grower

Weed Management

Primary Goal is to optimize yield by minimizing weed competition. Fast growing weeds that shadeblueberries provide the most competition

Weeds reduce yield by competing with the cropfor:

water

light

nutrients

No one method will control all weeds.

3

Weed Management

Primary Goal is to optimize yield by minimizing weed competition.

Three Primary weed management strategies are:

Prevention

Control

Eradication


Weed Management

Prevent production of seedsand other reproductive parts

Prevent weed emergence

Control growing weeds

Source: Aldrich and Kremer 1997

Less efficient

More efficient

4

Plant Growth Patterns

Growth TypeHerbaceousBroad leafGrass/sedge/rushWoodygrow in clumpspread by rhizomeLife CycleAnnual Biannual Perennial

Weed Management Principles

Prevention - preventing the spread of weed seedor vegetative parts and stopping emergence of weed seed present in the soil

Lowering pH to reduce weed growth

Cleaning field harvest equipment before moving into other fields

Cutting flower heads before seeds are formed

Use of mulch to prevent weeds from sprouting

Fertilizing to produce good crop vigor but not excessively to grow weeds

5

WEED MANAGMENTCultural: Lower pH to 4.0 for acid-loving plants

6.04.3

Problem with resistance

• Few preemergence herbicides available to control weeds i.e. Velpar, Sinbar and Diuron (Callisto only new product since 1983)

• Weed shifts documented and Canadian study documented wild oat grass becoming resistant to Velpar

6

SolutionSoil pH affectsNutrient availably

Metals more available and toxicAt low pH

Wild blueberriesadapted to low pHYield same

• Studies done with Cranberries by Patten in1996 and Roper in 1999 indicated acidification using sulfur reduced weed competition and lower rates of herbicides could be used to control weeds but slower to take effect and lasted longer

Studies on pH reduction

7

• To determine if reducing soil pH to 4 to control weeds and allow for the reduction in herbicide use

• Establish test sites throughout the state to evaluate different soil types and weed complexes experiment conducted from 2000-2006

Research done to test effect on wild blueberry

• In 2000, 2001, 2003 13 treatment sites were established. One site was discontinued.

• Plots on each site were treated with 0, 500, or 1000 lb/a of sulfur as 80% sulfur pellets

• In non-cropping years, plots were treated with either Sinbar or Velpar as 0, 0.5, 1, or 2 lb/a at a right angle to the sulfur treatments, weed cover evaluated in August after treatment

• Sites were evaluated for soil pH every year and weed cover was rated using a visual cover scale

Methods Sulfur/herbicide study

8

12

3

pH plot Locations

Assessment of Sulfur to reduce pH with Sulfur and herbicide treatments

500 S lb/a

0 0.5 1 2 lb/a

Velpar or Sinbar

No S

1000 lb/a S

9

0

1

2

3

4

5

6

Machiasport

pH from 2001 through 2005 from plot treated in 2000

Control 500 lb/a 1000 lb/a

Results

pH from 2001 through 2005 from plot treated in 2000

3.6

4.1

4.6

2001 2002 2003 2004 2005Treatment Year

pH

Appleton Rockport Machiasport Wesley-B Wesley-A

A )

3.5

4

4.5

5

2001 2002 2003 2004 2005Treatment Year

pH

Appleton Rockport Machiasport Wesley-B Weslety-A

A )

500

1000

Results sulfur on soil pH

10

4.3

4.4

4.5

4.6

4.7

4.8

4.9

5

5.1

5.2

5.3

0 lb/acre 500 lb/acre 1000 lb/acre

pH

Machiasport Wesley-S Wesley-V

Plots treated in 2000 – pH in 2006


4.24.3

4.44.5

4.64.74.8

4.95

5.15.2

0 lbs/acre 500 lbs/acre 1000 lbs/acre

pH

Blue Hill Franklin

Plots treated in 2003 pH in 2006


11

Results of herbicide on Grass Cover

0

5

10

15

20

25

30

35

2000 2001 2002 2003 2004 2005

Treatment Year

0 lb/a

0.5 lb/a

1 lb/a

2 lb/aA

B BB

aab

ab

b

A

BB B

Result of Sulfur on Grass

0

5

10

15

20

25

30

35

2000 2001 2002 2003 2004 2005Treatment Year

0 lb/a

500 lb/a

1000 lb/a

A

B

B

A

A

B

12

Results of herbicide on broadleaf Cover

0

5

10

15

20

25

30

2000 2001 2002 2003 2004 2005

Treatment Year

0 lb/a0.5 lb/a1 lb/a2 lb/a

A

BAB

B

A

B B

B

AAB

BB

Result of Sulfur on broadleaf cover

0

2

4

6

8

10

12

14

16

18

2000 2001 2002 2003 2004 2005

0 lb/a

500 lb/a

1000 lb/a

13

pH for cultural weed control

2004 Weed Cover Evaluation for Five Sulfur Treated Plots

0

5

10

15

20

25

30

35

Sulfur 0 lb/a Sulfur 500 lb/a Sulfur 1000 lb/a

Ave

rag

e W

eed

Co

ver

Grass

Herbaceous

Woody

Effect of Sulfur on Soil pH

2004 2005 2006

Y

0

1

2

3

4

5

6Soil pH

Control Sulfur

a aabbb

14

Organic Study: blueberry yield vs. prune method and pH reductioninteraction 2007

C

B B

A

0

500

1000

1500

2000

2500

Yie

ld (

lb/a

)

Mow - sulfur 0 lb/a

Mow - sulfur 1000 lb/a

Burn - sulfur 0 lb/a

Burn - sulfur 1000 lb/a

Granular Sulfur 90% - like Split Pea

pH reduction

15

Air Assist Applicator – most accurate placement

Vicon Applicator – more common for fertilizer

16

Pronone MG Spread Trial 2Mixture 200lbs DAP 10 lbs Pronone MG

Calibrate at 200lbs DAP 10 lbs Pronone at 30' width

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 410

100

200

300

400

500

Pronone MG DAP Target Pronone Target DAPCatch Pan

Vicon Fertilizer spreader gives uneven pattern

Proper Overlap 50%

Apply 1/2 target rateCover field twice

17

Wild blueberries are well adapted to a low pH environment

Reducing the pH in your soil gives the advantage to the wild blueberry over many weeds but will not suppress all weeds

Sulfur at approximately 100 lb/acre for a reduction of 0.1 pH unitis less expensive than an herbicide.

Change in pH may take several years to be completed

Results take longer to obtain but last longer

Take soil for pH test to determine amount of sulfur needed to reduce soil pH to 4.0

Retest and retreat as needed

pH reduction

New Weeds –Burnweed Pilewort T-19Erechtites hieracifolia

Question of source? Fertilizer ? Harvester ?Equipment?

Weed Management Prevention - sanitation

18

New Weeds –Burnweed Pilewort - E. MachiasErechtites hieracifolia

Question of source? Fertilizer ? Harvester ? Equipment?

Weed Management Prevention - sanitation

Seed dispersal by blueberry harvesters- Nova Scotia Study

Nathan Boyd & Scott White NSAC

• Seed dispersal within fields

• Seed dispersal between fields– Harvesters leaving or entering fields in NS (11)

– Harvesters entering NS from Maine (2)

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Seed Collection Points

• Tractor– Tractor grill

– Tires

– Inside cab


• Harvesting Heads– Bar on front of head

– Area surrounding hydraulic pump

– Top of head

– Bar behind brush

– Bar behind roller

– Shield along belt inside of head

20


• Belts– Loading belt

– Lift belt

– White guard on lift belt

– Metal sheet under top of lift belt


• Loading mechanisms– Berry leveler

– Blower

– Hydraulic loading bin

– Loading platform

21

Weed Seeds on Harvesters(Preliminary Results)

020000400006000080000

100000120000140000160000180000

shield on loadbelt

load belt lift belt

broadleafgrass

Tota

l wee

d se

eds

Weed Seeds on Harvesters(Preliminary Results)

0100000200000300000400000500000600000700000800000900000

1000000

broadleaf grass total

Tota

l wee

d se

eds

915,000

86% of seeds on or around the belts

22

Impact of pressure washing(Preliminary Results)

0

50000

100000

150000

200000

250000

300000

350000

shield on loadbelt

load belt lift belt

unwashedwashed

Tota

l wee

d se

eds

99 0 1833

Impact of pressure washing(Preliminary Results)

0100000200000300000400000500000600000700000800000900000

1000000

broadleaf grass total

unwashedwashed

Tota

l wee

d se

eds

98% decrease in seed number

19,321 1,501 20,821

23

Conclusions

• Probability of weed seed movement between fields on blueberry harvesters is high.

• Equipment sanitization should focus on key areas of the equipment.

• Pressure washing reduces seed loads up to 98%.

• Good example of Prevention


Control

Mechanical weed control -

mowcut pull

24


NO

25

How:Cut herbaceous weeds before go to seed

WEED MANAGMENT

Reproduction from SeedSeed Quantity

Species No. of Seed Survival(per plant) (years)

Wild oat 250 5Dandelion 15,000 6Prickly lettuce 27,900 9Lambsquarters 72,450 39Pigweed 117,400 10Mullein 223,200 39

26


Control

Cultural weed control

Surface mulch - bark, sawdust, peat, sand

Reduces surface temperatureand moisture loss – promotes blueberrySpread to keep weeds out

WEED MANAGMENTHow: Cultural: Mulch to reduce seed germination and promote filling in of blueberries

27

Radial spread of blueberry plants

Mineral Organic0

5

10

15

20

25

Inches



Fertilizing – take leaf samples at tip-dieback to determine plant nutrient needs

Only if N or PDeficient

Then addfertilizer

28

Yield as influenced by DAP application rate and P concentration in leaves

0 200 4004

5

6

7

8

0.105

0.115

0.125

0.135

0.145Yield X1000 P concentration



Fertilizing – NB Experiment increased fertilizer increase density and height of lambs quarters

29


Fertilizing – Velpar/DAP in Spring excessive rain (11” in May)leached Velpar but not fertilizer resulting in poor control in 2006

Weed Management Principles Chemical weed control

Control

Preemergence - target soil uptake

Postemergence - target plant

Nonselectve – but may apply selectively

Selective: grass and herbaceous broadleaf

Rotate herbicides to prevent resistance

30

Weed Management Principles Chemical weed control

Herbicide Class/Group Mode Weed Control Velpar S-Triazine 5 Photosynthetic better broadleaf and woody perennial Velossa inhibitor Sinbar Uracil 5 Photosynthetic better grasses and herbaceous perennial inhibitor Diuron Phenylurea 7 Photosynthetic annual broadleaf and grasses

inhibitor Callisto Triketones 27 HPPD pigment better on herbaceous broadleaf and sedges

inhibitor plant turns white

Fusilade Aryloxphenoxy ACCase inhibitor Grasses ONLY Propionate 1 inhibits fatty acid synthesis

Weed slowly breaks down as it is unable to build new cells Poast Cyclohexone 1 ACCase inhibitor Grasses ONLY Select Cyclohexone 1 ACCase inhibitor Grasses ONLY Glyphosate 9 Inhibits EPSP nonselective both grass, broadleaf and blueberry

Synthase prevents new amino acid synthesis Weed slowly breaks down as it is unable to build new cells

Express Sulfonylurea 2 Inhibits ALS Bunchberry ONLY prevents new amino acid synthesis Asulam Phenylcanbamate 18 inhibit cell division Bracken fern ONLY and expansion

Herbicide Resistance

• Survival of a segment of the population of a species (biotype) following an herbicide dose lethal to the normal population

31

0

50

100

150

200

250

1950 1960 1970 1980 1990

Year

Num

ber

of R

esis

tant

Bio

type

s

Increase in unique cases of herbicide-resistant weeds worldwide

Source: Ian Heap www.weedscience.com

Herbicide ResistanceHow does it occur?

0

25

50

75

100

1 2 3 4 5

Herbicide Dose

We

ed

Su

rviv

al (

%)

• Selection pressure

32

Herbicide ResistanceDevelopment of resistant weed population

Year Resistant Population Susceptible Population1 1 4,356,0002 4 435,6003 16 4,3564 64 4365 256 446 1,024 47 4,096 18 16,384 09 65,356 0

10 130,712 0

• 10 ac field - 10 weeds /sqft• 90% control• Annual quadrupling of resistant population


• Over 140 selective herbicides

• Only five basic modes of herbicide action

• 50% of all herbicides work on a single gene trait:

• blocking electron- transport in PSII

33

Number of Plant Biotypes Resistant to Herbicide based on Mode of Herbicide Action


• Development most likely when:– Herbicide is very active and efficient

– Weed seeds have short life in the soil seed bank

– Herbicide has a long soil persistence

– Herbicide is used frequently

34


• Development most likely when:– Herbicide rotation is not practiced

– Herbicide has single mode of action

WEED MANAGMENT

Preemergence herbicides: Velpar or Sinbar/Diuron in Spring before blueberries emerge April-MaySinbar better grass/sedge controlCallistoInhibits pigment formation onbroadleaf

Velpar has been used forOver 20 years, weed resistance and weeds that escape treatment develop

35

WEED MANAGMENTHow: Use optimal ratebest control not best returnMore not better

Preemergence : VelparToo much defoliates Blueberry plants

WEED MANAGMENTHow: Rotate herbicides: Sinbar/Diuron

36

Effect of Velpar and Sinbar/Karmex

on Grass and Herb Weed Cover - 2000

UTC 0.5 lbs/a 1.0 lbs/a 2.0 lbs/a0

10

20

30

40

50

60

Velpar-Herb Sinbar-Herb Velpar-Grass Sinbar-Grass

Untreated

37

1 Lb/a Velpar

2 Lb/a Velpar

38

1 Lb/a Sinbar/Diuron

Postemergence : Grass only Poast/Fusilade/Select broadcast or spot treatment in June-July

Herbicides appliedin crop oil conc. notwater soluble, will not leach.

WEED MANAGMENT

39

Postemergence Grass only Will take time to die, stops food productionPerennial grasses will require re-treatment At high rate

WEED MANAGMENT


Herbaceous Annual Perennial Grass/sedge/rush

40


Herbacous Annual Perennial Grass/sedge/rush



41


Herbacous Annual Perennial Rush/grass/sedge



42

OBJECTIVES• When broadleaf weeds are

controlled grasses are released and will increase

• Callisto does have some grass control but does not effectively control grass

• Two postemergence applications of Callisto at 3 oz/a are allowed per growing season

• We evaluated a tank mix of Callistoand Select 6 oz/a with surfactant

Spot treatments for broadleaf weed and grass control in blueberry fields using a Callisto/Select tank mix

Evaluation of Callisto + Select tank mix postemergence

• Locations: two commercial wild blueberry fields at BBHF in Jonesboro and at Wyman’s in Deblois

• Rates: – Callisto at 3 oz/a with Select 6 oz/a with a non-ionic surfactant at

0.25% v/v

• Timing: BBHF site was treated on 2 June and 10 July, while the Wyman’s site was treated on 16 June and 20 July – Wymans was developmentally behind BBHF

• Evaluated blueberry, broadleaf weeds and grass cover on:– BBHF: 9 June, 17 June, 20 July, 30 July– Wymans: 24 June, 2 July, 31 July, 6 August

43

Efficacy of weed spot treatments using a CallistoSelect tank mix on blueberry cover

0

10

20

30

40

50

60

70

80

90

100

Pre-treatment 9 or 24 Jun 17 Jun or 2 Jul 20 or 31 Jul 30 Jul or 6 Aug

June treatment July treatment

Evaluation timing

Blu

eber

ry c

ove

r (%

)

Mesotrione 3 oz/a +clethodim 6 oz/a

Check

non-parametric one-way median two-sample exact test, α=0.05

Callisto/Select tank mix efficacy on broadleaf weed cover

**

*

**

*

0

10

20

30

40

50

60

70

80

90

100

Pre-trt 9 or 24 Jun 17 Jun or 2 Jul 20 or 31 Jul 30 Jul or 6 Aug


Evaluation timing

Bro

ad

lea

f w

ee

d c

ov

er

(%)

Mesotrione 3 oz/a + clethodim 6oz/a

Check

non-parametric one-way median two-sample exact test, α=0.05

44

Callisto/Select tank mix efficacy on grass cover

**

**

0

10

20

30

40

50

60

70

80

90

100

Pre-trt 9 or 24 Jun 17 Jun or 2 Jul 20 or 31 Jul 30 Jul or 6 Aug


Evaluation timing

Gra

ss

co

ve

r (%

)

Mesotrione 3 oz/a + clethodim 6oz/a

Check

45

Both grasses and sedges controlled but new grass came in from seed

Environmental Factors

Excessive rain stimulated weed growth

2009 Maine Precipation

0

1

2

3

4

5

6

7

8

9

10

April May June July August September

Month

Inch

es

46

Treated plot at Wyman’s site - broadleaf weed and grass cover declining from evaluation one, 24 June to evaluation two, 2 July

Evaluation three, 31 July to evaluation four, 6 August blueberry filling in bare spots Regrowth/new growth of late-season broadleaf weeds and grasses

47

Weeds observed controlled

Black sedge Bentgrass spp.

Blue or Canada toadflax Colonial bentgrass

Brackenfern Wild or poverty oatgrass

Burnweed Witchgrass

Dewberry

Dwarf cinquefoil

Goldenrod spp.

Meadowsweet

Tall rattlesnake root

Whorled yellow loosestrife

WEED MANAGEMENT – Postemergence Selective

Goldenrod control in the non crop year with peremergence Velparand postmemergence Callisto.

Black bulrush control in the non crop year with postemergenceCallisto.

48

Goldenrods

Rough Canada Narrow-leavedGoldenrod Goldenrod Goldenrod

Photos: VMRP & Walter Wojtas

Application Rate

• Rate:– 6 oz/a in 20 gal/a water preemergence

– 3 oz/a with 1% COC postemergence

– Two applications at least 14 days apart

– Apply only in non-crop year

– Do not exceed 6 oz/a year

49

Sprayed at Budding Sprayed at 12”

Budding Flowering

50

Velpar No Velpar

Velpar

Callisto

51

Damage ratings and fruit buds Callisto with and without Velpar

Herbicide Goldenrod damage

Fruit Buds

------%------ ----No./stem----

Velpar 8.0 a 3.9 a

No Velpar 4.7 b 2.3 b

Summary• Callisto effectively controls some goldenrod

species at label rates if application timing is correct.

• Apply Callisto when goldenrod is at least 4 inches tall but before it begins to flower.

• Velpar followed by Callisto further reduced goldenrod density in the year of application and in the subsequent year.

52

Black Bullrush



53

Early Callisto 3 oz Late Callisto 3 oz

Late Callisto 6 oz

54

Effect of of black bulrush control on blueberry fruit buds

Treatment Fruit Buds----No./stem----

Control 1.0 b

Early Callisto 1X + Late Callisto1X

3.4 a

Summary

• Single applications of Callisto do not consistently achieve adequate levels of black bulrush control.

• Two applications of Callisto at label rates are required to achieve control of black bullrush

55

WEED MANAGEMENT – Postemergence SelectiveExpress for Bunchberry Control

Apply Express 1.0 oz/a in the fall to cropping fields only after blueberry harvest. There must be a minimum of 365 days between the application and the next harvest.

Express will only control bunchberry when adsorbed by its leaves, spray applications should only be made to portions of the field where bunchberry is present.

The herbicide may be used until a killing frost occurs, after which bunchberry will not be controlled

c c c

0

10

20

30

40

50

60

70

80

90

100

Check 28-Aug 14-Sep 5-Oct

% c

ov

er

2009 application date

Wild blueberry and bunchberry cover following Fall 2009 Express applications and Spring 2010 pruning

Blueberry cover Bunchberry cover

α=0.05 - two treatments compared

56

FOR DISTRIBUTION AND USE ONLY WITHIN THE STATE OF MAINE

DUPONTTM

EXPRESS® HERBICIDEwith TotalSolTM

(soluble granules)

EPA Reg. No. 352-632

SLN No. ME-080003

WEED MANAGEMENT – Postemergence SelectiveAsulox new herbicide for fern control

Maine 24 C label for the Asulox on Bracken Fern for non crop use for four years

Bracken should be in full frond prior to application.

Use Asulox only as a spot treatment at 1 gal/a.

Use of a non ionic surfactant at 0.25% v/v to improve uptake of the Asulox. Treatment is limited to non bearing fields so do not apply more than once every other year.

Control will be observed the year followingapplication of the Asulox. No visible controlsymptoms will be observed the year ofapplication.

57

Label on wild blueberry web site Under Factsheets/weeds/weed control labels

NON-SelectiveHerbaceous & woody weeds: 10%, 20% 33%Roundup with wiper or directed spray 1-2%

WEED MANAGEMENT – Postemergence

58

Proper application of roundup ortouchdown will prevent injury

Injury caused by Roundupor touchdown incorrectly applied

Identify Herbicide Injury

59

Blueberry re-growth after roundup injury

Identify Herbicide Injury


Eradication - elimination of all weed plantsand weed parts from area

Not practical if the weed is well established orif there are many of its seeds in the soil

Essential to identify new weeds early so there isa chance to eliminate them before they get established

Can save considerable future costs by identifying new weeds early

60

New Weeds – Dodder – parasitic weed

Weed Management

Dooder found in field in Mid-coast Region in 2006 suggested that it wason dogs Visiting from Massachusetts

Cranberry beds

Weed Identification Resources

Grays Manual of Botany, 1950. 8th Ed., M.L. Fernald,American Book Company, Boston.

Weeds, 1955. 2nd Ed., W.C. Muenscher, The Macmillan Company, New York.

Weeds of the Northeast. 1997. R.H.Uva, J.C. Neal & J.M.DiTomaso, Cornell University Press, Ithaca.

A field Guide to Wildflowers, 1968. M.T. Peterson & M McKenny, Houghton, Mifflin company, Boston.

Newcomb's Wildflower Guide, 1977. Lawrence Newcomb,Little, Brown and Company, Boston.

61

Weed ID Resource Sites

UMaine Blueberry weed imageshttp://umaine.edu/blueberries/factsheets/weeds/

New Brunswick Department of Agriculture and Aquaculture http://daamaaextweb.gnb.ca/010-002/Default.aspx?Culture=en-CA

Wild Blueberry Network http://nsac.ca/wildblue/facts/weeds.asp

Weed Research Information Centerhttp://weedid.wisc.edu/ca/

Weed Mapping

Weed mapping techniques used in cranberry bogs

62

Weed Mapping

Obtain NRCS aerial photo enlargement or sketch your ownmap

Weed Mapping

Use Google Earth to provide you with a map of your field

63

Weed Mapping

Note Area of weed presence

Species:identify or classify type

Abundance:fewcommonabundant

Size:smalllarge

Weed Mapping




Size:smalllarge

64

Weed Mapping




Size:smalllarge

Weed Mapping




Size:smalllarge

65

Weed Management

Prevent production of seedsand other reproductive parts

Prevent weed emergence

Control growing weeds

Source: Aldrich and Kremer 1997

Less efficient

More efficient

Estimated Costs and Returns for Treatments Treatment Rate/a $Cost $Return ____________________________________________ Velpar 1lb 50 1500 Sinbar 2lb 90 1500 Diuron 2lb 30 750 Callisto 6oz 55 1500 Roundup 20%wipe 20 750 Express 1oz 40 300 Asulox 1gal 60 2000 ____________________________________________________ Assume $20/a application cost and $0.50/lb blueberry price

66

Estimated Costs and Returns for Treatments Treatment Rate/a $Cost/yr $Return ____________________________________________________ Cutting 50 1500 Sulfur 1000lb 50-200 3000 Mulch 20% cover 150 600 ____________________________________________________ Assume organic return $3/lb and sulfur and mulch cost over 10yr

Thank You • David Yarborough

• Blueberry Specialist

• Professor of Horticulture

• University of Maine in Orono

• 1-800-897-0757

• [email protected]

• www.wildblueberries.maine.edu

Documents

Wild Blueberry Best Management Practices for Weeds