Organic Blueberry Production

8/9/2019 Organic Blueberry Production

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IS A PROJECT OF THE NATIONAL CENTER FOR APPROPRIATE TECHNOLOGY

By George L. Kuepper & Steve DiverNCAT Agriculture SpecialistsUpdated by K. Adam, February 2000

Introduction

The following is anintroduction to organicblueberry production,designed tosupplementinformation fromconventional sourceson basic cultivationpractices. Matters suchas pruning, training,variety choice, sourcesof propagation

material, and plantingare essentially the samein both organic andconventional culture.Generic blueberryinformation can beobtained from theCooperative Extension Service and commonhorticultural texts and periodicals.

The word organic has precise legal definitions inmost states, and there are certification groups that

maintain standards for what can be certified andmarketed as organically grown, as well asprescribed record-keeping procedures. An

organic certification agency or organic growersorganization should be contacted to determineexact requirements and a list of prohibitedpractices and substances.

However, some smaller

producers may wish tofollow organicpractices withoutbecoming formallycertified. Theinformation providedhere should be usefulto them, as well.

This publication isgenerally applicable toorganic culture of all

three cultivatedblueberry species.Information onimproved blueberrycultivars is continuallybeing released byresearch and extensionagencies.

800-346-9140

A ppropriate Technology Transfer for Rural Areas

ORGANICBLUEBERRY

PRODUCTION

www.attra.ncat.org

Abstract: This publication focuses on organic production practices for blueberry culture, with someinformation on marketing outlook. A list of resources includes websites.

ATTRA is the national sustainable agriculture information center funded by the USDAs Rural Business -- Cooperative Service.

Contents

Introduction ................................................... 1Soils and Fertility............................................ 2

Cultural Considerations.................................. 6Pests............................................................... 8(chart) ................................................... 10

Diseases.......................................................... 9(chart) ................................................... 11

Bird and Rodent Control................................. 9Marketing ....................................................... 9Summary ........................................................ 9References...................................................... 12

Additional Resources...................................... 13

Additional ATTRA publications onorganic certification include:Organic Certifiers Resource ListResources for Organic Marketing

HORTICULTUREPRODUCTIONGUIDE


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// ORGANIC BLUEBERRY PRODUCTION Page 2

In the Far North, low-bush and dwarf highbushblueberry cultivars are more climaticallyadapted than are highbush types. The lowbushwild blueberry (V. angustifolium) iscommercially important in Maine. The WildBlueberry Association of North America(WBANA) website(http://www.wildblueberries.com) promotesmarketing and is an excellent source of

information on production practices.

Blueberries have fewer pest problems than mostother fruits, offering an advantage for organicproduction. Most insect and disease problemscan be controlled through cultural manipulation.Blueberries have a relatively low nitrogenrequirement and thrive on organic sources.Adjusting soil pH low enough and protectingfrom predatory birds and mammals are the majorproduction constraints. Weather fluctuations andgeographic seasonal advantage are the majoreconomic considerations.

Generally, non-organic transplants can be usedfor establishing perennial crops. However, mostcertifiers require the plants to be grown at least 12months under organic conditions after trans-planting before any harvested product can bemarketed as organic.

Soils and Fertility

The Importance of Soil pH

Blueberries are distinct among fruit crops in theirsoil and fertility requirements. As members ofthe Rhododendron family, blueberries require anacid soil, preferably in the 4.85.5 pH range. The

reasons for this are several. First of all, when soilpH is appreciably higher than 5.5, iron chlorosisoften results; when soil pH drops below 4.8, thepossibility of manganese toxicity arises. In eithercase, plants do not perform well.

Soils with a native pH above 5.5 pose specialproblems for organic producers. Recurrentapplications of acidifying agents are necessary inorder to keep pH from drifting back to its naturallevel. Non-organic methods may depend on

acidifying agents such as ammonium sulfate ordi-ammonium phosphate which are not allowedunder organic certification criteria. Not allcertifiers allow the usual flowers of sulfur andferrous sulfate for pH correction in organicculture. Acceptable substitutes are cottonseedmeal (from organic cotton) and, if pH is not toohigh, sawdust or pine needle mulches, which canassist in lowering pH a few tenths of a unit.

Soil pH also plays a significant role in crop

nitrogen management. Research has shown thatblueberries are preferential to soil and fertilizernitrogen in the ammonium form, absorbing andutilizing it much more efficiently than nitratenitrogenthe form preferred by most othercommercial crop plants. Neutral and basic soilsfavor nitrificationthe rapid conversion ofammonium nitrogen to nitrate through theactivity of nitrifying microorganisms. When anacidic soil environment is maintained, theammonium form of nitrogen predominates and isreadily available to blueberries.

This principle also applies to the addition ofsupplemental nitrogen fertilizers. Conventionalrecommendations routinely emphasize the use ofammonium fertilizers, particularly ammoniumsulfate, which also acts as a soil acidifier. When aslow-release organic fertilizer like fish meal isapplied, the nitrogen in the proteins is converted

For more information about marketing

options, see the ATTRA publications DirectMarketing and Farmers Markets. On-farmvalue-added blueberry products usually

require setting up a second rural enterprisebesides farming, and may entail considerableadditional planning, management, and start-

up expense.

Rabbiteye (Vaccinium ashei)adapted type inthe South (roughly south of Interstate 40).

Highbush (V. carymbosum)adapted tointermediate climates.

Southern highbush (V. ashei x carymbosum)


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first into ammonium. The ammoniumwhichwould rapidly convert to nitrate under neutralsoil conditionstends to remain in the desired,ammoniated form.

One preferred method of lowering soil pH inorganic culture is application of sulfur. Pre-plantincorporation of sulfur to lower the pH to anoptimal blueberry range of 4.85.5 should bebased on a soil pH test. Because soil pH is subjectto considerable seasonal fluctuationespeciallyon cropped soilsit is advisable to do soilsampling and testing in winter or very earlyspring, when biological activity is at a low level.

The table below provides guidelines for sulfurapplication on different soil types.

Powdered sulfur takes about one year to oxidizeand reduce soil pH. Prilled sulfur takessomewhat longer. Limestone, too, requires timeto effect changes in pH and reactive time ishighly dependent on the fineness of grind.

Single applications of sulfur should not exceed400 pounds. Best results are obtained byapplying 200 pounds in spring, followed by 200later in the fall for as many intervals as isrequired to deliver the total amount. It is

advisable to re-test the soil one year after eachapplication to determine if additionalacidification is truly necessary (2).

Organic growers are advised to be conservativein the application of soil sulfur. Sulfur has bothfungicidal and insecticidal action and can

detrimentally affect soil biology if overused.Organic growers sometimes increase theirapplications of peat moss at planting time as it,too, is a soil acidifier (pH 4.8), reducing the needfor sulfur. The Ozark Organic GrowersAssociation suggests as much as 510 gallons ofpeat moss per blueberry plant. While costly, peatis resistant to decomposition and provides thebenefit of soil humus.

Those seeking alternatives to spaghnum peatmoss might consider the use of pine bark orsimilar amendments incorporated in the plantingrows or holes. While viewed as less desirablethan spaghnum peat moss, pine bark can often beobtained locally at a much lower cost. A new

commercial substitute for peat called coir, madefrom coconut fiber pith, appears promising, butonly if it becomes available at a reasonable price.

It is advisable to monitor soil pH over time asproduction practices can cause gradual changesto occur. Irrigation water often contains calciumand magnesium, which may cause soil pH tocreep upwards, while repeated use of acidifyingfertilizers, such as ammonium sulfate orcottonseed meal, may lower pH. Fortunately, the

presence of abundant organic materials such aspeat and the breakdown products of sawdust andwoodchip mulches tend to buffer soil pH.(Several organic growers have even observed thatblueberries grown in high organic matter soilswill perform well at a pH as high as 6.0 with fewapparent problems.) As a result, additional

Approximate pounds per acre of sulfur or ground limestone to change soil pH one unit (1).

Soil Texture Pounds per acre of sulfur tolower soil pH one unit (e.g. 6.0 to 5.0)

Pounds per acre of lime to raisesoil pH one unit (e.g. 4.0 to 5.0)

Sand (CEC=5) 435 to 650 1000

Loam (CEC=15) 870 to 1300 2800

Clay (CEC=25) 1300 to 1750 4400


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NATURAL MATERIALS FOR SUPPLEMENTARY FERTILIZATION

Material Estimated NPK Characteristics

Alfalfa meal 3 12 Good trace mineral source.

Blood meal 121.30.7 Medium N release rate of 68 weeks.

Cottonseed meal 722 Slow to medium N release of 46 months. Soilacidifier

Feather meal 1300 Slow N release of 46 months

Fish meal 1022Slow to medium N release of 46 months.

Leather meal 1000 Slow N release. Restricted use in organics due toheavy metal contamination.

Compost and compost-

blended fertilizers

Analysis is highly variable depending on raw materials in compost and materials

added to fortify the blend. Analyses commonly range from less than 1% toabout 8% N. Considered a slow-release source of N, but preferred overall as afertilizer.

sulfur (or lime for that matter) is seldom needed.When it is needed, top dressing is usually done,but delivery of soluble sulfur through dripirrigation lines is also an option.

Blueberry Fertilization Practices

Soil building practices prior to establishment cango a long way towards providing the fertilitynecessary to a healthy blueberry planting. Highlevels of soil organic matter are especiallyimportant in blueberry culture, contributing tothe soils ability to retain and supply moisture tothe crop, buffering pH and releasing nutrientsthrough the decay process. Organic-rich soils arealso a desirable environment for symbiotic

mycorrhizal fungi that assist blueberry roots inabsorbing water, nitrogen, phosphate and otherminerals. Cover crop and green manures canplay an important part in cycling organic matterinto the soil system, as can applications ofcomposts and livestock manures. ATTRA hasseveral publications which can be useful in these

areas including Overview of Cover Crops and GreenManures and Farm-Scale Composting Resource List.

Once a blueberry planting is established,supplemental fertilization can be applied in anumber of forms and by several means.Generally, supplemental nitrogen is the greatestconcern, followed by potassium. Blueberries havea low phosphorus requirement and typicallyrequire little, if any, phosphorus fertilization. Infact, excessive phosphate has been one of thefactors linked to iron chlorosis in blueberries.High calcium levels are also consideredproblematic.

Nitrogen fertilizer recommendations vary

somewhat from region to region. As a generalguideline, 100120 lbs. of nitrogen per acre arecommonly recommended on mulched berries; areduced rate of 5060 lbs. per acre is advisedwhere little or no mulch is used (3). Nitrogen isoften applied in three split applicationsone atbud break, followed by two more at six week


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intervals. These recommendations apply toconventional soluble fertilizers, and adjustmentsmay be appropriate for less-soluble organicfertilizers. One rule of thumb suggests thatorganics be applied from 14 weeks ahead of theschedule recommended for soluble fertilizers.This allows additional time for decompositionprocesses to make nutrients available.Applications after mid-July are discouraged, asplants tend to develop late growth that isparticularly sensitive to freeze damage. A tableof natural materials used by organic growers forsupplementary fertilization is provided onp. 10 (4).

Current fertilization practices among organicgrowers vary considerably. In one example (5),an organic blueberry grower in the MissouriOzarks applies 1/2 pound of feathermeal per

mulched plant in late May of the establishmentyear followed by a similar application 46 weekslater. In subsequent years, an additional (third)application of 1/2 pound feather meal is madeearlier in mid to late March. As the feather mealproducts available in this region contain roughly13% nitrogen, this grower is applying approxi-mately 141 pounds of actual N per acre in theestablishment year, and an annual total of 212pounds per acre thereafter .

Using the same schedule of split applications,another organic grower in the Arkansas Ozarks,also growing mulched berries, applies cottonseedmeal (estimated at 7% N) at 1 lb. per plant eachtime. At these rates this grower is applyingroughly 152 lbs. per acre N in the establishmentyear and about 229 lbs. per acre in subsequentyears (6). (It should be noted that the use ofcottonseed meal in certified organic production iscontroversial because cotton is one of the mostheavily sprayed agronomic crops and thepresence of residues is a concern. In addition,

certified organic growers should specify"mechanically extracted" cottonseed meal and not"chemically extracted" or "solvent extracted"cottonseed meal.)

Associate professor John Clark (3) at theUniversity of Arkansas believes the fertilizationrates used by these organic growers are probablyexcessive. Despite the slower availability of

organic-based nitrogen, the carry-over fromprevious seasons should result in roughly thesame amount of nitrogen released each season asis being applied. But since detailed research islacking, no one can be certain of the best rates touse.

Clark suggests that the best way to determine

whether fertilization rates are on target is toannually test foliar nitrogen levels. This isaccomplished in late July or early August (inArkansas) by sampling leaves from the mid-shoot area on fruiting canes and sending them toan appropriate laboratory. Lab results showingnitrogen levels below 1.6% indicate a nitrogendeficiency; a level in excess of 2.2% indicatesnitrogen excess. This service is available throughCooperative Extension in Arkansas and severalother states. Several commercial laboratories also

provide foliar analysis. ATTRA can provide ashort list of laboratories that offer various soiland plant tissue testing services.

Potassium needs in blueberries are oftenprovided through decaying mulches. The needfor further supplementation should bedetermined by soil and/or tissue testing. Whereadditional potassium is needed, it may be appliedin a number of formsincluding sul-po-mag,epsom salts, granite meal, and greensand. Thelatter two sources are relatively low in availablepotash and are not usually advisable from aneconomic standpoint if potash supplementationis the sole objective. Since chloride-basedfertilizers have proven detrimental to blueberries,natural sources of potassium chloride (thoughacceptable to some certifying agencies) shouldnot be applied in significant amounts.

An all-around good blueberry fertilizer is highquality compost. Depending on the humuscondition and biological activity in the soil,

compost may be able to provide all the fertilityneeds of the crop. Where compost is of averagequality, it may still function as a good soilconditioner. The use of aged animal manures inblueberry production is also possible, but is lesscommon.

Fertigation of blueberriesthe practice ofinjecting soluble fertilizers through drip irrigation


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linesis a common practice in conventionalproduction. Since fertigation is based on thecomplete solubility of fertilizers in water, thereare limited options among organic fertilizers.Attempts at fertigation with blood meal byArkansas blueberry growers have resulted inclogged emitters and algae growth. Morerecently, however, researchers in Californiademonstrated the use of spray-dried fish proteinand poultry protein in drip systems (7). Inaddition, several liquid fertilizers used by organicgreenhouse growers (Green JuiceTM, Simeon'sSuper TeaTM) look promising.

As previously mentioned, the root systems ofblueberry plants are also limited with regardto where they grow within the soilagroecosystem. Unlike the roots of grapes andbramble fruits, which extend well into the

interrow area, blueberry roots are confined to azone much closer to the row. As a result, allfertilizers and amendments must be appliedunder the plant canopy to assure that theyreach the roots.

Foliar feeding of blueberries is practiced by someorganic growers and is especially helpful whenplants are stressed or not thrifty. Foliarfertilization programs usually consist of seaweedand fish emulsion. The Ozark Organic Growers

Association has recommended a seaweed-fishmix applied three times per growing seasonatbud break, just prior to harvest, and just afterharvest. More detailed information on foliarfertilization technology is available from ATTRA,on request.

Cultural Considerations

Plant spacing

Highbush blueberries are typically spaced 44 feet in the row, with 812 feet between rows. Asbushes can get quite large at maturity, manygrowers find that 1012 foot row spacingsapproximately 900 to 1090 plants per acrearepreferable for tractor operations (mowing,harvesting, spraying). Rabbiteyes are typicallyspaced at 58 feet in a row with 1214 feetbetween the rows, or 388 to 726 plants per acre.

Dr. J.N. Moore and others at the University ofArkansas have experimented with denser within-row plant spacings for highbush blueberries,effectively doubling the number of plants peracre. Yields during the first five years afterplanting were found to be substantially higher (aboon to the overall economics of blueberryproductionespecially where high investmentsin bird netting, etc. have been made).

These researchers have been careful to point out,however, that beyond the fifth year, inter-plantcompetition may create problems, requiringremoval of every other plant in the row (2).Fortunately, highbush blueberries transplanteasily, and removed bushes can be used inestablishing another field.

Interrow Management

The root system of the blueberry is not extensive.As a result, clean cultivation of row middles tocontrol weeds and to incorporate cover crops isless damaging to blueberries than it is to bramblefruits. Still, it is wise to till no deeper than 3inches. Similarly, interrow living mulchesalsocalled sodded middlesare generally notcompetitive with the crop unless the speciesemployed are aggressive and invade the rows.Fescue is commonly used in the Mid-South for

sodded middles, though several other grassspecies are also in use.

Timely mowingusually 35 times per yearisthe common means of controlling weeds andother vegetation in sodded middles. It is mostimportant that weeds not be allowed to produceseed which may be scattered into the rows togerminate later.

In a Texas study, researchers demonstrated that

the interrow area could be utilized to producesignificant quantities of mulch for rabbiteyeblueberries. Successful winter crops of rye,ryegrass, and crimson clover, and a summer cropof pearl millet, were grown, cut, and windrowedonto the blueberry rows. Nitrogen proved themajor limiting factor for non-leguminous covercrops. Low soil pH and browsing by deer limitedthe biomass production of legumes. Pearl millet


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demonstrated the greatest level of allelopathicweed suppression (8).

In many systems which employ sodded middles,a weed-free strip about 612 inches wide is oftenmaintained between the edge of the mulch andthe cover crop. The strip reduces competitionbetween cover crop and crop, and lessens thechance that weeds or the cover crop itself willadvance into the mulch. It has the added bonusof discouraging cutwormsan occasional pest inblueberries. In conventional systems, this strip ismaintained through the use of herbicides.

Organic growers typically employ mechanicalcultivators of various types. Gordon Watkins (9)describes two modified off-the-shelf cultivatorsused by growers in the Ozark region. One,referred to as the Vasluski Edger, uses a single disc

from a rice levee plow in conjunction with twoshanks from a spring-tooth chisel. These aremounted on a tool-bar which extends past therear tractor tire. The disc cuts a strip along therow edge and throws soil towards the plantswhile the shanks stir soil closer to the bed. Theresult is a weed-free strip about 68 inches wide.The drawback of this implement is the amount ofdirt shifted by the disc and the resulting ditchwhich remains.

The second implement Watkins describes is theLilliston Rolling Cultivator, with all the headsremoved except those two extending beyond therear tire. One head rolls in the ditch area that is(or would be) created by the Vasluski Edger disc.The second extends approximately 12 inches ontothe side of the bed. Depth of penetration is set at1 inch and it is best operated at relatively highspeeds. Since it cultivates about one-half of thebed surface, only about a 2foot strip remains forhand-pulling and hoeing. The tool works well on

small weeds but does not control larger, well-established weeds.

In-Row Weed Management and Mulching

As in other perennial fruit crops, weeds can buildto damaging levels in blueberry plantings. It isespecially important to control aggressiveperennial weeds such as johnsongrass,

bermudagrass and quackgrass prior to cropestablishment. Details of pre-plant and post-plant weed management for all fruit plants areprovided in ATTRA's Overview of Organic FruitProduction. Some techniques, however, deserveadditional detail.

In much of the country blueberries are grown onraised beds and mulched. Raised beds reducethe incidence of soil- and water-borne diseases.Thick mulches provide weed suppression, soiltemperature regulation, slow-release nutrients,organic matter and moisture conservation. Thelatter is especially important because blueberryroots lack root hairsthe primary sites for waterand mineral absorption on most plants. Thischaracteristic makes water management ofparamount concern and goes a long way towardsexplaining why irrigation and mulching are

recommended practices.

The importance of maintaining a weed-free zonearound blueberries was demonstrated in aGeorgia study (10) using rabbiteye blueberriesconsidered to have a more vigorous rootsystem than highbush types. Researchersdetermined that an optimum vegetation-freezone during the first 23 years of growth extendsto roughly 1.52.5 ft from the plant. Thistranslates to a 35 ft wide weed-free row bed,

whether maintained by mulch, tillage, herbicides,or some other means.

The Georgia study appears to confirmconventional practices which have evolved inrecent years. Current recommendations suggestmulching a 34 foot-wide strip to a depth of 35inches with sawdust, bark, wood chips, or woodshavings. Organic growers often prefer a deepermulch of up to 6 inches over a strip at least 4 feetwide. Ideally, the mulch should be sufficiently

coarse to minimize crusting, and the surfacerelatively flat to encourage water penetration andgas exchange.

While the mulch suppresses many weeds, thereare some that find this habitat hospitable.Among these are several perennials that canbecome persistent and troublesome. Tractor-drawn cultivation implements are somewhat


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impractical for in-row weed control on deep-mulched blueberries. This is especially true sinceblueberry roots often grow into the mulch andsignificant plant damage can result from tillage.Shallow hoeing or hand-pulling weeds are twotraditional options practiced by organic growers.

Other organic options that might be considered

include spraying a natural herbicidal productsuch as soap-based ScytheTM or Safer Superfast.In a similar vein, the Kerr Center for SustainableAgriculture (11) in Oklahoma has experimentedwith concentrated vinegar solutions. Soap-basedproducts and vinegar are contact herbicideswhich burn down the sprayed vegetation.They are most effective against small, annualweeds and seedling perennials. Damage toblueberries should be minimal if the spray isproperly directed below the canopy to the base of

the crop and if drift is properly controlled. Sincethese products vary in their chemical make-upand their legal and practical uses, all pesticidelabeling should be thoroughly read and theappropriate certifying agency consulted forapproved usage in organic production.

Weeder geese are another possibility for weedmanagement. Weeder geese can eliminate mostof the grass and many of the tender broadleafweeds from a planting. They are prone to eatingripe fruit, however, and may damage some of thenewly emerging canes, so their use should betimed accordingly. Obviously, stocking rates aremuch lower, and management easier on cleancultivated plantings. Investigators at the KerrCenter for Sustainable Agriculture have usedweeder geese for effective weed control inblueberries with sodded middles. Their strategyentails use of movable electric fencing andintensive grazing. One possible drawback citedby Kerr Center researchers was the tendency ofgeese to compact soil and mulch. ATTRA can

supply further information on weeding withgeese, on request.

An alternative to organic mulching that looksvery promising is the use of geotextile fabricweed barriers. While fabric mulches may notprovide all the benefits of a deep organic mulch,they are highly effective for weed control; andthough the initial cost is high, it may prove

reasonable when amortized over the expectedlifetime of 1012 years.

Note that non-porous, black plastic mulchescommonly used in vegetable productionare notrecommended for blueberries. The reasoncommonly given is that polyethylene plasticmulch encourages surface rootingmaking the

plants more susceptible to drought stress andwinter injury.

Some research has also been done on flameweeding in blueberriespresumably on non-mulched plantingsin Michigan (12, 13).Damage to crop plants proved a problem whichwas alleviated considerably using a water sprayto shield the crop. Researchers do not appearespecially optimistic about the use of flameweeding in blueberries at this time and it is

unclear whether research continues. Pleaseconsult ATTRA's Overview of Organic FruitProduction for further details of these and otherweed control options.

Refugia

Cover crops and adjacent vegetation may act ashabitat to populations of beneficial insects whichprovide pollination and help to suppress pestinsects and mites. In blueberries, increasing thenumber of pollinators can be quite important.Wild bees (carpenter bees, bumblebees, orchardbees, etc.) are the most efficient pollinators ofblueberries. Several varieties of blueberryrequire, and almost all varieties yield better as aresult of, cross-pollination. When crops and fieldborders are managed with beneficials in mindthey are often referred to as refugia, and representa new approach to pest management based onplanned biodiversity. To learn more aboutrefugia, request the ATTRA publication entitledFarmscaping to Enhance Biological Control.

Arthropod Pests

Rabbiteye blueberries seem more tolerant ofinsect damage than highbush varieties. The mostcommon insect problem is the blueberry maggot.Although insect damage in blueberry plantingsrarely reaches economic thresholds, regularmonitoring by walk-throughs and use of insect


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traps is advised. See chart 1 (p. 10) for moreinformation.

Diseases

Diseases common to blueberries include mummyberry, Botrytis, stem blight, stem canker,phytophthora root rot, blueberry stunt, andseveral virus diseases. For proper diseaseidentification, consult Cooperative ExtensionService publications and related literature. Manystates also have pathology laboratories associatedwith Cooperative Extension that can provideassistance. For a summary of blueberry diseasesand their control, see chart 2 (p. 11).

Bird and Rodent Control

Birds are often serious pests of blueberries.

Various methods of control have beentriedincluding "scare-eye" balloons, MylarTM

reflective tape, sonic devices, etc.with varyinglevels of success. The problem with mostrepellents or scare tactics is that birds becomehabituated to the stimulus, and are not scared off.Sometimes, growers overcome this problem bychanging the stimulus frequentlye.g.,switching from balloons to MylarTM tape ormoving the balloons from one site to another.Properly applied bird netting has provided

consistent and predictable control, but isexpensive to purchase and set up (materials costfor 1/3 acre planting in 1992 was $659.11) (14).An Illinois study (15) found the yield increase onnet-protected blueberries paid 80% of the costs ofinstallation at a problem site. As growers reporta 10-year life expectancy for netting, theinvestment proved profitable by the second year.

Various rodents can be problematic inblueberries, primarily voles which feed on rootsand bark. Several other soil dwellers such asmoles and shrews may also be present. These arelargely carnivores which feed on grubs andworms; however, their tunneling can proveharmful to the plants. Rodent problems arelargely confined to plantings that are mulchedand those with permanently sodded middles.Clean cultivation provides little shelter anddisturbs burrows. Organic alternatives include

trapping, encouraging predators (e.g. setting outperches to attract raptor birds), frequent mowingof sodded middles, and managing fencerows andadjacent areas to discourage in-migration (16).

For details on options for rodent control, pleaserefer to ATTRAs Overview of Organic FruitProduction. This publication also discusses

management of bird problems. CooperativeExtension and the U.S. Fish and Wildlife Servicealso have information on rodent and bird controloptions.

Marketing

In the mid-90s consolidation in the food industryleft fruit growers fewer marketing options. Theselarge corporate buyers demanded that growersprovide larger units of higher quality fresh

product. For instance, frozen blueberry exportsto Japan tripled in 1997. The North AmericanBlueberry Council launched a feasibility study fora national promotion and research program forblueberries (17). The Councils website (seeElectronic Resources, below) has industryinformation, including statistics, future prospects,promotional materials, and data on markets,including consumer, food service, and export.

According to recent market reports in The Packer,

a considerable amount of fresh blueberries arebeing imported from Chile during the wintermonths, providing year-round availability forAmerican consumers. However, the demand fororganically grown fruit has continued toincrease (18).

A breakthrough in value-added marketing camein the late 90s with scientific research indicatingspecial health benefits of blueberry consumption.This research, conducted at the USDA HumanNutrition Research Center at Tufts University,

continues (19). More farmers are now looking aton-farm value-added products.

Summary

Blueberries adapt well to organic culture. Costsof production may be somewhat higher usingorganic methods but this might be effectively


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Chart 1: Insect Pests and ControlsInsect

Caterpillars:Gypsy mothBagwormLeafrollersCranberry fruit worm

Pesticide

Bt var kurstaki

Remarks and other controls

Apply when insects are feeding.

Fruit worms Bt var kurstaki

Pyrethrum spray*


Must target adult flies before they lay eggs.24 hours pre-harvest interval.

Cranberry fruit worm Elimination of weeds and vegetative litter aroundplants helps cut down on overwintering protectionfor fruitworm cocoons. In small planting with lightinfestations, can be effectively controlled by pickingoff infested berries, which are easily detected becauseof the webbing and their early ripening.

Blueberry maggot Sticky traps can be used to monitor maggot in adultstage. Sustained catch of several adult flies per weekindicates that it is an optimal time to make aninsecticide treatment.

Japanese beetles Pyrethrum spray*

Sabadilla dust or WP

24 hour pre-harvest interval.

Dust: apply to wet plants

Clean harvesting prevents accumulation of overripefruit, helping to prevent beetles from being attractedto plantings. Use pheromone lure-traps near but not

in the planting. In small planting with lightinfestations, can be effectively controlled by pickingbeetles off the bushes by hand.

Leafroller Bt var kurstaki

Pyrethrum spray*


24 hour pre-harvest interval.Mites Ultra-fine horticultural oil Foliar spray.

Scale insects Ultra-fine horticultural oil Dormant spray; remove canes weakened by scales.Monitoring can be done by wrapping sticky tape,sticky-side out, around twigs. Light-colored crawlersshow up well if dark tape is used such as black

electrical tape.

*Some cerfifiers restrict the use of pyrethrums to special situations; certain formulations may be prohibited.Most certifiers do not allow botanical pesticides to be used as the primary method of pest control.


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Chart 2: Blueberry diseases and their control.

Fungal diseases

Mummy berry (Monilinia vacinii-corymbosi) Fungus overwinters in mummified berries that have fallen to the ground. Sod ormoss directly under the plant will contribute to spore production. To control this fungus, remove infested fruit ("mummies") fromthe plant, rake and burn the mummified berries, or cover the fallen berries with at least two inches of mulch. Cultivation during themoist spring weather will destroy the spore-forming bodies.

Botrytis Blight (Botrytis cinerea) The fungus survives the winter on dead twigs and in soil organic matter. The disease is moresevere when excessive nitrogen has been used, where air circulation is poor, or when frost has injured blossoms. Cultivarspossessing tight fruit clusters are particularly susceptible to this disease. Remove dead berries, debris, and mulch during the winterand compost it or destroy it. Replace with new mulch. Do not place mulch against the trunk of the plant.

Anthracuose (Colletotrichum acutatum and C. gloeosporioides) The fungus overwinters in dead or diseased twigs, fruit spurs, andcankers. Spores are released in the spring and are spread by rain and wind. Cultivars in which the ripe fruit hangs on for a longtime on the bush prior to picking are especially susceptible. Removal of infected twigs by pruning, and frequent harvesting arebeneficial to control. Old canes and small twiggy wood should be removed in order to increase air circulation around the fruitclusters.

Botryosphaeria Stem Blight (Botrysphaeria dothidea) Removal of infected wood, pruning about 12 inches below the discoloredpart of the limb, is the only practical control. Since infection can be spread throughout the growing season, prune duringdormancy. Fertilizer management is necessary to prevent formation of succulent shoots late in the growing season. Infection ofcold-injured shoots around the base of the bush is a primary means by which this fungus enters the plants. The worst cases of stemblight occur on soils that are extremely sandy or on heavy muck soils that promote excessive growth. Genetic resistance is availableand should be a primary consideration in the establishment of new plantings

Rust (Pucciniastrum vaccinii) Remove and burn infected vegetation. Multiple reinfestations possible during one growing season.Native evergreen berries (but not hemlock) are suspected as the overwintering source and a necessary alternate host for completionof the fungus life cycle. It may be beneficial to remove native Vaccinium species from lands adjacent to cultivated bushes.

Phytophthora Root Rot (Phytophthora cinnamomi) Control includes use of clean nursery stock and good field drainage. Heavysoil that becomes waterlogged or has a high water table should be avoided. Plants can be grown on raised beds to reduce risks. Norecognized method for elimination of disease organism without use of soil fungicides.

Phomophis Twig Blight (Phomopsis sp.) The fungus overwinters in infected plant parts. Spores released from old cankers in thespring; rain is necessary for spore release; temperatures ranging from 7080 degrees F encourage infections; moisture stresspredisposes the plant to infection. The disease is most severe after winters in which mild spells are interspersed with cold periods.Remove and destroy infected plant parts by pruning. Avoid mechanical damage such as that caused by careless pruning andcultivating. Avoid moisture stress by use of irrigation during dry periods. A fall application of lime sulfur (allowed by someorganic certifiers) after leaves have dropped help reduce disease inoculum. Spring application of lime sulfur should be made earlybefore warm weather occurs to avoid injury to plants. Refer to your state's spray guide for recommended rates and timing. Carefulcultivar selection can greatly reduce the amount of twig blight experienced.

Fusicoccum Canker (Fusicoccum sp.) The fungus overwinters in cankers. Spores are largely disseminated by rainwater. Coldstress may play a part in increasing disease damage. Removal of infected plant parts is essential for control. Varieties differ in theirresistance to this disease.

Viral diseases

Shoestring Disease Other than buying disease-free plants, destroying wild plants near the planting, and removing diseasedplants, control does not exist. Some cultivars possess genetic resistance or tolerance.

Stunt -- The only known carrier is the sharp-nosed leafhopper, though other vectors probably exist. Diseased bushes cannot becured. They must be removed from the field as soon as they are diagnosed. Agitation of the bush during removal will dislodge theleafhoppers, causing them to move to a neighboring healthy bush.

Bacterial disease

Bacterial Crown Gall (Agrobacterium tumefaciens) The crown gall bacterium does not grow well in an acid situation, thus thedisease is uncommon where soil pH is maintained in the optimum range for blueberries


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counterbalanced through premium market sales.Many cultural practices, such as the use of deepmulching and sodded row-middles, arerecommended for both conventional and organicblueberry production systems reflecting a moresustainable approach to commercial horticulture.Additional relevant information on growingblueberries is available through CooperativeExtension and other conventional sources.ATTRA can assist in providing further subjectmatter relating to organic and sustainableapproaches.

References:

1) Whitworth, Julia. 1995. Blueberry Helps:Fertilizing Blueberries. Issue 1. In: HorticultureTips. Oklahoma State University CooperativeExtension. Stillwater, OK. March.

2) Pritts, Marvin and James Hancock (ed.). 1992.Highbush Blueberry Production Guide.Northeast Regional Agricultural Guide.Northeast Regional Engineering Service,Ithaca, NY. 200 p.

3) Clark, John. Associate Professor ofHorticulture, University of Arkansas atFayetteville. Personal communication. March18, 1997.

4) Information in this table was taken from

Organic Fertilizer NPK Values Compiled, byRoss Penhallegon, in the January 1992 issue ofIn Good Tilth (p. 6); and Nitrons ProductGuide for Natural Fertilizers & SoilConditioners, published by Nitron Industries,Fayetteville, AR (no date).

5) Moore, J.N. , M.V. Brown and B.P. Bordelon.1994. Plant spacing studies on highbushblueberries. Arkansas Farm Research.JulyAugust. p. 89.

6) Watkins, Gordon E. 1988. Organic BlueberryCulture. Proceedings of the Seventh AnnualOklahoma Horticultural Industries Show.January 2829. p. 4551.

7) Schwankl, Lawrence J., and Glenn McGourty.1992. Organic fertilizers can be injectedthrough low volume irrigation systems.California Agriculture. SeptemberOctober.p. 2123.

8) Patten, Kim, Gary Nimr and ElizabethNeuendorff. 1990. Evaluation of living mulchsystems for rabbiteye blueberry production.HortScience. Vol. 25. No. 8. August. p. 852.

9) Watkins, Gordon. 1989. Non-toxic weedcontrol in blueberries. Ozark OrganicGrowers Association newsletter. May. p. 67.

& JuneJuly. p. 6

7.

10) NeSmith, D. Scott and Gerard Krewer. 1995.Vegetation-free area influences growth andestablishment of rabbiteye blueberry.HortScience. Vol. 30. No. 7. December. p.14101412.

11) The Kerr Center for Sustainable AgricultureP.O. Box 588Poteau, OK 74953918-647-9123

12) Hansen, C.M. and W. Gleason. 1965. Flameweeding of grapes, blueberries, and straw-berries: A progress report. Proceedings of theSecond Annual Symposium: Use of Flame inAgriculture. p. 1112.

13) Hansen, C.M., W. Gleason and J. Hull. 1966.Flaming research. Proceedings of the ThirdAnnual Symposium: Use of Flame inAgriculture. p. 2526.

14) Anon. 1992. Bird-proof blueberries. FreshPicks. FebruaryMarch. p. 56.

15) Anon. 1991. Cost-effectiveness of anti-birdnetting for blueberries. HortIdeas. April. p. 42.

16) Hauschild, Karen I. 1995. Vole managementin small fruit plantings. Northland BerryNews. December. p. 2224.

17) Staff. 1994. Recent downsizing of Americanbusiness changing face of the blueberryindustry. Great Lakes Fruit Growers News.

April. p. 32.

18) Torrice, Caleb. 1999. Organically grown blue-berries rising in demand. Cornell CooperativeExtension Small Fruit News of Central NewYork. August. p. 1.

19) Staff. 2000. Blueberry elixir reverses age-related symptoms. Agriculture Research(USDA). February. p. 23.


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Additional Resources:

Austin, M.E. Rabbiteye Blueberries: Development,Production and Marketing. AgScience Inc.,Auburndale, FL.

AgScience Inc., 206 W. Bridgers Ave.,Auburndale, FL 33823. (863) 967-8898. $39.

Baker, M.L. and K. Patten (eds.). 1990. TexasBlueberry Handbook. Texas A&M , Overton, TX.Approx. 100 p.

Marty Baker, P.O. Box 38, Overton, TX75684. $12.50 (text only),$15 (3-ring binderw/index tabs). Make check payable to BlueberryPublications, Acct. 237202. (903) 834-6191.

Caruso, Frank L. and Donald C. Ramsdell. 1995.Compendium of Blueberry and Cranberry Diseases.APS Press, St. Paul, MN. 87 p.

Doughty, C.C., E.B. Adams, and L.W. Martin. 1981.

Highbush Blueberry Production. Washington-Oregon-Idaho Cooperative Extension Service Bulletin. PNW215.

Eck, P. 1988. Blueberry Science. Rutgers Univ. Press,New Brunswick, NJ. 284 p.

Eck, P. and N.F. Childers (ed.). 1966. BlueberryCulture. Rutgers UP, New Brunswick, NJ. 378 p.

Galletta, Gene J. and David G. Himelrick (editors).1990. Small Fruit Crop Management. Prentice Hall,Englewood Cliffs, NJ. 602 p.

Gough, R.E. 1995. The Highbush Blueberry and ItsManagement. Food Products Press, NY. 272 p.

Johnston, S., J. Mouten, and J. Hull, Jr. 1969. Essentialsof Blueberry Culture. Michigan State UniversityExtension Bulletin. E-590.

Moore, J.N. 1976. Adaption and Production ofBlueberries in Arkansas. Arkansas AgriculturalExperiment Station Bulletin. No. 804.

Pritts, Marvin and J.F. Hancock (ed.). 1992.

Highbush Blueberry Production Guide. NE RegionalAg Engineering Service, Ithaca, NY. 200 p.

Scott, D.H., A.D. Draper, and G.M. Darrow. 1978.Commercial Blueberry Growing. USDA Farmers'Bulletin No. 2254. US Gov. Printing Office,Washington, DC. 33 p.

Torrice, Caleb. (annual update). Blueberry ProductionSummary. Cornell Coop. Extension, Ithaca, NY. 6 p.

Electronic Resources:Alternative Opportunities for Small Farms: BlueberryProduction Review. University of Florida.http://hammock.ifas.ufl.edu/txt/fairs/ac/1360.html

Fruit and Nut Review: Blueberries. Mississippi StateUniversity.http://www.ces.msstate.edu/pubs/is1448.htm

Michigan Blueberry Growers.http://www.blueberries.com

North American Blueberry Council.http://www.blueberry.org

Northwest Berry & Grape Infonet. Oregon StateUniversity. http://www.orst.edu/dept/infonet/

Suggestions for Establishing a Blueberry Planting inWestern North Carolina. North Carolina StateUniversity.http://www.ces.ncsu.edu/depts/hort/hil/hil-201.html

U.C. Fruit & Nut Research and Information Center.

University of CaliforniaDavis.http://pom44.ucdavis.edu

Wild Blueberry Association of North America.Bangor, ME. http://www.wildblueberries.com

By George L. Kuepper & Steve DiverNCAT Agriculture SpecialistsUpdated by K. Adam, February 2000

The electronic version of Organic Blueberry

Production is located at:

http://www.attra.org/attra-pub/blueberry.html

The ATTRA Project is operated by the National Center for Appropriate Technology under a grant from theRural Business-Cooperative Service, U.S. Department of Agriculture. These organizations do notrecommend or endorse products, companies, or individuals. ATTRA is located in the Ozark Mountainsat the University of Arkansas in Fayetteville at P.O. Box 3657, Fayetteville, AR 72702. ATTRA staffmembers prefer to receive requests for information about sustainable agriculture via the toll-freenumber 800-346-9140.


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