Growing Raspberries in Wisconsin (A1610 ) - Polk

B R I A N R . S M I T H , D A N I E L L . M A H R , P A T R I C I A S . M C M A N U S , T E R Y L R . R O P E R

GROWING RASPBERRIESIN WISCONSIN

A1610

Rubus ideaus

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CONTENTS

The raspberry plant . . . . . . . . . . . . . . . . . 2

Site and soil selection . . . . . . . . . . . . . . . . 3

Cultivar selection . . . . . . . . . . . . . . . . . . 4

Plant source . . . . . . . . . . . . . . . . . . . . . . 6

Planting . . . . . . . . . . . . . . . . . . . . . . . 6

Soil fertility program . . . . . . . . . . . . . . . . 7

Mulching . . . . . . . . . . . . . . . . . . . . . . . 7

Irrigation . . . . . . . . . . . . . . . . . . . . . . . 7

Training . . . . . . . . . . . . . . . . . . . . . . . . 8

Pruning . . . . . . . . . . . . . . . . . . . . . . . 10

Insect management . . . . . . . . . . . . . . . . . 13

Disease management . . . . . . . . . . . . . . . . 15

Weed management . . . . . . . . . . . . . . . . . 19

Problem solving . . . . . . . . . . . . . . . . . . 19

Related publications . . . . . . . . . . . . . . . . 21

RaspberriesI N W I S C O N S I N

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T art, juicy and flavorful,raspberries are a welcome addition to the home garden orcommercial planting in Wisconsin. Red and yellow raspberry

cultivars can be grown throughout the state. Purple raspberriesshould be grown only in the lower two-thirds of the state. Black

raspberries should be planted only in the southern quarter of the state,and even then, only in good sites.

Well-established, vigorous, disease- and insect-free plantings arehighly productive. Yields of 1 to 2 quarts per plant (2500 to

3000 pounds of fruit per acre) are common and provide a ready source of fruit forhome use or supplementary income from direct on-farm or pick-your-own sales. Commercial

production of raspberries should be limited to red and purple cultivars and should be developed onfavorable sites near potential pick-your-own and pre-picked markets.

THE RASPBERRY PLANTRaspberries can be categorized as one of twofruiting types: summer-bearing or fall-bearing.Summer-bearing types produce one large cropbetween early July and early August. Many ofthe common red and most of the common blackand purple cultivars are summer bearing. Fall-bearing raspberries, sometimes incorrectly calledever-bearing, produce a large crop in the fall anda smaller crop the next summer. Typically, how-ever, fall-bearing raspberries are mowed annu-ally, so they bear fruit only in the fall.

The difference between these two types is due tothe fruiting cycle of the plants. Raspberries haveperennial (long-lived) roots and crowns butabove-ground canes that live for only two sum-mers. In the first summer of growth, the newcane is called a primocane. On summer-bearingraspberries, the primocane produces vegetative(non-fruiting) growth only. Fall-bearing raspber-

tipsfloricane (second-year cane)

side branches

primocanes (first-year canes)

crown budsroots

crown

ANATOMY OF A RASPBERRY PLANT

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ries bear fruit on the tips of the primocanessometime after August 1. Fruit development con-tinues inward and downward on the primocanesuntil the first killing frost.

In the second summer, the primocane thatemerged the previous year is now called a flori-cane. In summer-bearing cultivars, this floricanewill produce one large crop in late summer andthen die. In fall-bearing raspberries, the cane thatemerged and fruited the previous fall will fruitthe rest of the way down the cane and then die.

Since primocanes emerge each year and growconcurrently with the floricanes, fruit productioncontinues year after year for both fruiting types.The only difference is that any one cane on asummer-bearing raspberry has only one crop; ona fall-bearing cultivar it has two crops.

Raspberry flowers are self-fertile, which meanspollen originating from one cultivar can causefruit set on any plants from the same cultivar.Bees are attracted to the profuse amounts of nec-tar produced in raspberry flowers and areresponsible for 90–95% of pollination.

Red raspberries and black raspberries are sepa-rate species, while purple raspberries are hybridsbetween the two. Most yellow raspberries arenatural color variants of red raspberries and areidentical to them in every other way.

Red and yellow raspberries produce numerousnew canes from “crown buds” at the base of flor-icanes and from buds distributed randomly onthe roots. Thus, the many emerging suckershoots will produce a dense, ill-defined plantingunless plants are confined to their allotted loca-tion by pruning and cultivation.

Black raspberries and most purple raspberriesproduce primocanes only from the crown buds atthe base of floricanes. Because these plants donot sucker, the clumps or “hills” remain in theoriginal planting location.

Raspberry canes are round with small thorns andsometimes numerous prickles. Many thornlessraspberries are not suited to Wisconsin’s climate.

SITE AND SOIL SELECTIONRaspberries grow best in full sunlight on an airysite sheltered from direct winds. Poorly drainedareas where water stands after a rain are notacceptable. To decrease disease and insect prob-lems, isolate cultivated raspberries from wildraspberries or blackberries, and plant them infields that have been free of wild raspberrieswhenever possible. Also, raspberries, strawber-ries, and solanaceous plants (tomatoes, potatoes,and eggplants) share many of the same diseases.To reduce the risk of diseases carrying over tonew plantings, wait at least 3 years before plant-ing on these sites.

Good air circulation and air drainage improveraspberry plantings. Air circulation around theplants helps them dry quickly after dew, rain, orirrigation. Ideally, raspberries should be plantedon a slope or hillside so that the heavier cold aircan drain and settle into lower areas. Springfrosts are less likely to damage a planting if coldair can drain away.

Raspberries perform well on most mineral soilsthat are moderately fertile, well drained and eas-ily cultivated. A deep, sandy loam high inorganic matter (5–7%) is ideal. Light sandy soilsare also acceptable if irrigation is available.Raspberries do best in slightly acidic soils with apH of 6.0 to 6.8. They will produce satisfactorilyat a soil pH between 5.5 and 7.5, however.

Summer-bearing red raspberries tolerate wintertemperatures of –30°F or lower when the plant isfully hardy or acclimated. This crop suffers injurymost severely during winters with fluctuatingtemperatures. On warm winter days, the darkraspberry canes absorb heat from the sun and arewarmed above the air temperature injuring tis-sues and buds, especially those growing on southslopes. To minimize this exposure, summer-bear-ing raspberries will perform best if planted on anorth slope or on the north side of a windbreak.

In Wisconsin, plant fall-bearing red raspberrieson a south slope or protected location to promoterapid growth of primocanes and early fall fruiting.

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CULTIVAR SELECTIONSelecting winterhardy, productive raspberry cul-tivars is an important ingredient for success.Hardiness refers to a plant’s ability to withstandwinter conditions—both low and fluctuatingtemperatures and desiccating winds. Select culti-vars adapted to Wisconsin’s rigorous and unpre-dictable winter climate. The cultivars describedbelow are listed in order of ripening within eachsection. The preferred growing regions are listedin parentheses after each cultivar name.

Summer-bearing red raspberriesRed raspberries are most common in Wisconsin,with many adapted cultivars available.

Boyne (N&S) The tender, medium-sized fruit isglossy and dark red with good flavor. Good forprocessing and fresh use. Moderately vigorouscanes are sturdy, winterhardy, and very produc-tive. Boyne is best suited for trellis training sys-tems where fruiting canes are tied to wires on theoutside of rows. Above-average yields.

Nova (N&S) Medium-large, bright red, fruit ofgood quality, somewhat acid. Good for fresh useand freezing. Good winter hardiness, few prick-les. Above-average yields.

Festival (N&S) Glossy, bright red fruit ismedium sized and very attractive. Very good forfresh use, fair for freezing. Short but vigorous,nearly spineless plants have good winter hardi-

ness. Immune to mosaic virus, tolerant of spurblight, and susceptible to late leaf rust. Highyielding.

Killarney (N&S) Medium-large, bright red fruitwith good flavor. Good for freezing. Fruit tendsto soften in hot weather. Canes are spiny andsucker readily. Susceptible to mildew andanthracnose. Very high yields.

Reveille (S) Large soft fruit has very good flavorfor fresh use, but is only fair for freezing.Vigorous canes tolerate fluctuating winter tem-peratures. Average yields.

K81-6 (S, trial) Very large, firm fruit has verygood flavor. Resistant to powdery mildew andlate yellow rust. Tolerant to crown gall, but suscep-tible to fruit rots, fire blight, and Phytophthoraroot rot. Medium-tall canes with few spines at base.

Latham (N) Medium-large fruit is an attractive,bright red color. It is very good for canning andfreezing, but somewhat crumbly for fresh eating.Fruit ripens over a long period. Vigorous plantsare productive and have excellent winter hardi-ness. Requires trellis. Tolerant to several viruses.

Haida (S, for trial N) Dark red fruit are larger,firmer, and sweeter than Boyne. Very good freshor processed. Vigorous plants sucker prolificallyand have very few spines. High yield potential.

Fall-bearing red raspberriesFall-bearing raspberries are recommended for thesouthern two-thirds of the state where the grow-ing season is longer. Early fall-bearing cultivarscan be planted in the northernmost areas, butfrost may ruin the crop before the total potentialharvest is complete.

Summit (N) Small to medium-sized fruit isbright red, firm, and glossy with very good fla-vor. Excellent for processing. Ripens in earlyAugust, making Summit a good choice fornorthern Wisconsin. Vigorous canes require atrellis.

N

S

Northern and southerngrowing regions

for Wisconsin


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Autumn Britten (N&S, trial) This new cultivarhas uniform medium to dark red fruit. Higheryields and better flavor than Autumn Bliss.Vigorous plants have sparse spines.

Autumn Bliss (N&S) Considered the standardfor fall-bearing raspberries in Wisconsin. Theselarge, dark red fruit have a pleasant, mild flavor,but are soft and somewhat crumbly. Canes arevigorous and spiny and typically produce higheryields than Heritage. Ripens mid-August.

Ruby (S, for trial N) The largest fruit of the fall-bearing red raspberries for Wisconsin. The berriesare dark red, moderately firm, and slightly tart.Vigorous, productive canes produce numeroussuckers and sparse spines. Yields are equal to orbetter than Heritage. Requires a well-drained soil.

Caroline (N&S, trial) Large red berries haveexcellent flavor and shelf life. Good vigor, moder-ate suckering, and higher yields than Heritage.Better tolerance to yellow rust and root rots thanHeritage. Long fruiting season.

Heritage (S) The fruit is firm and medium-sizedwith good quality. Ripens late August in south-ern Wisconsin. Typically lower yielding thanAutumn Bliss and Summit. The canes are sturdy,vigorous, and hardy. Performs best in warm, shel-tered locations.

Black raspberriesBlack raspberries are marginally hardy in southernand eastern Wisconsin and thrive only in favor-able locations. Black raspberries originated fromthe American black raspberry. They are not ashardy as red raspberries but, if properly managed,they will produce acceptably. The berries have adistinctive flavor with prominent, hard seeds.

Blackhawk (S) Vigorous plants with medium-sized, good quality black berries. Productivityvaries according to winter injury. Fairly resistantto anthracnose.

Bristol (S) Suggested for trial. Producesmedium-large, firm, glossy black fruit. Widelyplanted but not hardy in Wisconsin except onfavored sites.

Purple raspberriesPurple raspberries are hybrids of red and blackcultivars. They grow similarly to blacks but aremore vigorous and significantly hardier. Theberries are large and of good quality, though usu-ally less attractive than red cultivars. They aregood fresh and excellent for freezing. Withproper cultural practices, purple raspberries willproduce substantial amounts of fruit.

Amethyst (S) Fruit is shiny and moderatelylarge, but tends to be soft. Highly productive andvigorous. Adapted for home use or on-farm sales.

Brandywine (S, for trial N) Reddish-purple fruitis large, firm, and very tart. Fair for fresh use,excellent for jams, jellies, and freezing.Brandywine is not fully hardy even in southernWisconsin.

Royalty (S, for trial N) Produces large, attractivepurple fruit which may be harvested in the redripe stage. Berries are sweet with better flavorthan Brandywine. Excellent for processing orfreezing. Needs protection from winter injury; itis not fully hardy even in southern Wisconsin.Resists aphids, a primary carrier of virus diseases.

Yellow raspberriesYellow-fruited cultivars are rarely as productiveas red-fruited types. May be difficult to obtain.

Honeyqueen (N&S, trial) A high-quality sum-mer-bearing raspberry with large yellow fruit.Medium height canes sucker freely.

Anne (N&S, trial) Fall-bearing raspberry withlarge, light yellow fruit. Excellent flavor andgood firmness. Good vegetative vigor and sparsesuckering. Relatively low yields.


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Plant sourceAvoid the temptation to start new plantings froman existing planting. These plants may harbordiseases and insects that are not readily apparent.Purchase plants from a reliable nursery to be surethey are true to name, vigorous, healthy, and dis-ease free. Such plants grow better, produce morefruit, and live longer. But remember, althoughthese plants start out disease free, they are notimmune to diseases. You will still need to takeprecautions to avoid infecting the planting withviruses and other diseases that will weaken theplants.

Nurseries propagate stock using one of twomethods: by digging suckers from the originalparent plants to sell as bare root stock andthrough tissue culture. Tissue-cultured stock isgrown from a small piece of the desired cultivarand grown in a sterile environment. Tissue-cul-tured plantings typically bear fruit earlier, pro-duce more fruit, and live longer than bare rootcane stock plantings.

If you choose to propagate your own stock, beaware of plant patent restrictions. It is illegal topropagate cultivars that are still protected under17-year plant patents (even for home use) unlessyou are licensed to do so.

PLANTINGSelect the planting site 1 to 2 years before plant-ing. Check for adequate internal soil moisturedrainage and install drainage tile if necessary.Add large amounts of organic matter such asmanure or green vegetation. If persistent triazineherbicides such as atrazine or simazine havebeen used, wait a year before planting. Controlperennial weeds with nonresidual systemic her-bicide applications or frequent cultivation. Get asoil test from the site. Before planting, incorpo-rate any recommended nutrients—especiallyphosphorus, potassium, and lime. Soil phospho-rus should be 25 ppm (parts per million); soilpotassium should be 100 ppm. Plow or rototillthe planting site the fall before planting. To pre-vent erosion, you can plant the site to rye.

Plant bare-root cane stock as early as possible inthe spring, but after danger of temperaturesdropping below 20°F has passed. Tissue-culturedstock is particularly tender, so wait until all riskof frost is past before planting (normally whenone would transplant tomatoes into the garden).

For both types of stock, prevent root exposurewhen the soil settles by setting the plants in ahole or furrow slightly deeper than they weregrown. Pack the soil firmly around the roots andwater them well. Tissue-cultured plants requirefrequent shallow irrigation throughout the firstgrowing season.

The favored planting system in Wisconsin is the“narrow hedgerow.” Set red raspberries every 2to 3 feet in rows at least 6 feet apart. Set blackand purple raspberries every 2 to 3 and 2 to 4feet, respectively, in rows that are at least 8 feetapart. Allow new red raspberry shoots to spreadalong the row but do not let them spread widerthan 12 to 15 inches at the row base. Wider rowsare hard to weed and prune and invite diseasesthat thrive in damp, slow-drying conditions.Maintain a 2- to 3-foot weed-free strip on eitherside of the raspberry row and permanent sod inthe remaining space between rows.

Red raspberries can be grown in the “hill” sys-tem. “Hill” refers to the cluster of canes thatdevelops around a single plant. It does not meansetting the plant in a mound of soil. Set theplants in holes 4 to 5 feet apart in each directionand allow new shoots to spread to a diameter ofabout 1 foot.

With proper care and normal weather conditions,a raspberry planting can remain productive for12 to 15 years. When the planting begins todecline (small, crumbly fruits; stunted plants;low yields; weedy areas), plow it up and replantin a new location, if possible. If not, wait a yearor two before replanting in the same site.

SOIL FERTILITY PROGRAMWell-fertilized, healthy plants have tall, thick,new canes, dark green leaves, and high qualityfruit. To make the soil more fertile, plow under acover crop, such as clover or soybeans, or 1000 to1500 pounds of stable manure or compost per1000 square feet. Fall plowing to a depth of 8 to10 inches is preferred. Early in the spring, culti-vate the soil until it is in good planting condition.

If you did not plow down manure or a covercrop, and if the soil is not already fertile, work acomplete fertilizer thoroughly into the soil beforeplanting.

Preplant fertilizer applications should be basedon soil test results. Information on how to take aproper sample and submit samples for testing isavailable at your county Extension office.Extension publication Sampling Lawn and GardenSoils (A2166) outlines these procedures.

On new plantings, after plants are well estab-lished, broadcast 2 to 4 pounds ammonium sul-fate (21-0-0) or 11⁄2 to 2 pounds urea (46-0-0) per100 feet of row or scatter 1⁄4 cup in a band18 inches wide around each plant.

Established plantings on well-prepared sitesshould require only nitrogen fertilizer. Apply 1 lbammonium sulfate or 1⁄2 lb urea per 100 feet ofrow before growth begins. Repeat 3–4 weekslater. In hill plantings, apply 1⁄2 cup complete fer-tilizer around each plant group.

To encourage maximum growth early in the sea-son, apply all fertilizer in very early spring beforegrowth starts. Avoid fertilizing after August 1 asthe nutrients will encourage succulent newgrowth late in the season, making them moresusceptible to winter damage. For more specificfertilizer recommendations, refer to FertilizingSmall Fruits in the Home Garden (A2307), availablethrough county Extension offices.

MULCHINGIn Wisconsin, a mulch is desirable in the estab-lishment year on most soils. It helps retain soilmoisture, suppresses weeds and reduces soilheaving in winter. Avoid mulching poorlydrained heavy clay soils as the mulch will keepthe roots too wet.

If mulch is expensive or scarce, use it only in therows around the hills, and cultivate the areabetween the rows. Where water is readily avail-able for irrigation, sod can be allowed to developbetween rows. Use an approved herbicide tomaintain bare soil around plants if growing sodbetween rows.

Chopped hay, straw, and stable manure are goodmulches, but they are likely to be full of weedseeds. Instead use old silage, leaves and lawnclippings, wood chips, sawdust, wood shavings,or rye or sudangrass straw, which are usuallyfree of weed seeds.

Stable manure used as a mulch also adds nutri-ents, so avoid applications after June 15 that maykeep the plants growing too late in the fall.Apply other mulches whenever they are avail-able, but avoid smothering young suckers in thespring. Mix 1⁄4 to 1⁄2 cup ammonium sulfate orurea fertilizer per bushel of sawdust or woodshavings to speed mulch decomposition and toprotect against plant nitrogen deficiency.

Mulch should be spread no thicker than 2 inchesdeep to discourage rodents from nesting in it.

IRRIGATIONRaspberries produce better quality and higherquantities of fruit. They are also typically lesssusceptible to disease and insect infestations ifgiven adequate water throughout the growingseason.

Raspberries obtain most of their water from thetop foot of soil. Frequent, shallow irrigations arebetter than occasional, deep watering. Frombloom until harvest, raspberries growing inloamy soils need about 1 to 11⁄2 inches of water

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every 7 to 10 days either from rain or irrigation.Raspberries growing on sandy soils shouldreceive 1⁄3 to 1⁄2 inch of water every 3 to 5 days.Fall-fruiting cultivars need adequate moisturethroughout the summer to help them formprimocanes and fruit. Low winter soil moisture isa major cause of damage and plant loss, so irri-gate thoroughly before the soil freezes if late fallrainfall is inadequate and the soil is dry.

You can irrigate raspberries with overhead sprin-kler irrigation or with drip or trickle irrigation.Overhead sprinkler irrigation also can providefrost control to extend the harvest season of fall-bearing raspberries. Use tall risers to get sprin-klers above the plants. Overhead irrigation mayaggravate some disease problems.

Although drip irrigation has not been usedextensively in raspberry production, it canenhance growth and productivity in Wisconsin.Drip irrigation typically uses plastic pipe or tapewith emitters or nozzles at regular intervals. Theamount of water applied is regulated by the typeand number of emitters and the duration of theapplication. Drip irrigation requires a clean, fil-tered water supply to prevent clogging. Drip ortrickle systems apply water more evenly andmore efficiently than does overhead irrigation.

Added benefits include fewer disease problemsbecause foliage remains dry and fewer weedproblems because between-row areas are notwatered. Drip systems cost less initially than dosprinkler systems, but they cannot be used forfrost control.

TRAININGTraining raspberries provides a number ofadvantages compared to untrained hedgerowplantings. Training makes picking easier, sup-ports fruiting canes to keep berries off the soil,improves pest management and most impor-tantly, enhances light interception for maximumproduction of large, high quality berries. Beforechoosing a trellis system, carefully evaluate costsof material and labor.

Hill system. With this systemset a permanent stake—metal ortreated wood—in the center ofeach hill. Tie the canes loosely tothe stakes at the top of the caneswith heavy twine after you havepruned them. Wait to tie youngshoots or suckers until after prun-ing in late fall or winter.

Narrow-hedgerow sys-tem. With the narrow-hedgerow training sys-tem, a trellis is used to hold canes upright. Thesimplest system uses single or double wires.Stretch heavy-gauge galvanized or aluminumwire between permanent posts set 20 to 30 feetapart in the row. You may use either one wire,two wires at different heights, or two wires at thesame height. Place the canes between the wiresto eliminate tying (figure 1). If the wires spread,hold them together with a hook of wire. Fastenone end of the hook loosely, but permanently toone wire and bend the other end to hook overthe remaining wire. You can move these hookseasily along the wire where they are mostneeded. If you use a single wire or one wireabove the other, tie the canes loosely to the wiresafter pruning.


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FIGURE 1. A permanent trellis. Cedar posts (4 to 6 inchesin diameter) are placed about 20 feet apart. Set posts atleast 24 inches into the ground.

48”-60”

40”-

45”

24”

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Trellis crossarm or “T” trellises allow maximumlight penetration and greatest productivity. Tyingfruiting canes to wires on a “T” or crossarm trel-lis keeps fruit to the outside of both sides of therow, making picking easier. Primocanes aredirected towards the middle while floricanes areanchored to the wires on either side to make har-vesting easier. Maximum light in the row centerhelps develop strong, vigorous fruiting canes forthe following season, and doesn’t interfere withthe current season’s harvest. Permanent metal ortreated wood fence posts should be set 20 to 30feet apart in the row. Make crossarms 24 to 32inches long out of scrap oak at least 1-inch thick,pipe or angle iron. Treated 2 x 4 inch lumber isalso satisfactory for crossarms but may be moreexpensive than other materials suggested. Attachcrossarms to posts 48 to 60 inches from the soil.You will need to alter crossarm height on posts toconform to cane vigor and height of canes.

A simple method for maintaining trellis wire ten-sion uses simple straight link chains to adjustwire tension (figure 2). Attach a heavy-dutyspring, available from farm supply stores,between each chain and wire to maintain con-stant tension and avoid frequent wire tightening.

Chain link tighteners make it easy to removewires, which is helpful for pruning. To simplifyremoving old fruiting canes or thinning canes indormant pruning, lift wires from the trellis arms.After pruning or thinning, replace the wires onthe trellis arms, then tie selected fruiting canes towires at spacings of 4 to 6 inches along the wires.

For vigorous cultivars or narrow row spacing ofplantings, double “T” trellises provide addedsupport for fruiting canes (figure 3). Use upperarms the same length as for the single “T” trellis.Lower arms generally are shorter (12 to 15inches) and are attached to posts at approxi-mately 24 inches above the soil. Lower arms helpcontain new growth in the center of the row andbetween upper wires. Lower crossarms alsoreduce cane sagging, improving ease of culturaloperations such as weed control or mowingalong the plant hedgerow.

To hold canes upright, spiral a piece of string orlight twine along the length of a single trelliswire, placing canes in the spiral. You will need tocut the string before removing floricanes afterharvest. Double wires on each side of the uppercrossarms will also hold canes upright. After

FIGURE 2. Straight linkchain allows wire tightening,removal and replace-ment at pruning.

FIGURE 3. A double “T” trellisholds canes in a narrowhedgerow. Double wires oneither side of the uppercrossarm hold caneswithout tying.


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pruning, place dormant canes between the twowires. Sufficient tension on both wires shouldhold canes with adequate force to prevent windwhipping or sliding along the wires. Doublewires on each side of the trellis arms may be usedon any of these training systems and will largelyeliminate the need to tie canes to wires.

The “V” trellis system (figure 4) provides thesame advantages of increased productivity, easeof harvest and improved pest control as the “T”trellis systems. Additional costs for posts may beoffset by eliminating the need for crossarms.Metal T-posts are also suitable for this system.

For most raspberry trellis systems, 12-gauge gal-vanized wire is strong and durable enough forlong-term use. High tensile steel wire, availablefrom specialty fencing suppliers, permits extratensioning of wires with superior supportstrength. For short rows of 20 feet or less, heavyplastic twine will also do.

In all cases, trellis end posts should be largerthan line posts and adequately braced to supportwire tightening and crop loads. To ease harvest-ing and cultural operations, trellis rows shouldbe no longer than 300 feet to permit cross trafficand equipment turning.

PRUNING

Pruning summer-bearing red raspberriesSummer pruning. Immediately after the lastharvest, cut out at ground level and remove allcanes from the planting that have just borne fruit.These floricanes will die soon anyway, andremoving them eliminates a disease source andgives new shoots more room to grow. Thin newshoots at this time, leaving three or four of thesturdiest canes per foot of row (or six to eightcanes per hill in the hill system). Do not cut backthe cane tips until the following spring when youcan determine die-back and winter damage.

Dormant pruning. Make this pruning in thespring after danger of winter injury passes butbefore new growth begins. If you haven’t alreadypruned the old canes and thinned the new shootsas described for summer pruning, do so at thistime.

Cut back slightly any side branches on theremaining fruiting canes. Also cut back the tips ofthe fruiting canes slightly. This is called “headingback” and prevents the canes from becoming topheavy. Severe heading back greatly reduces thecrop, therefore never cut off more than one-fourth of the cane. At this time cut off any tipsthat died back in winter.

Biennial bearing. This pruning system is theeasiest and least time consuming way to maintainsummer-bearing raspberries, though yields arelower. Each year during the dormant season, cutoff half of the planting. Choose a contiguous sec-tion or cut alternate rows throughout the plant-ing. Yields are typically reduced by only 30%rather than the expected 50% since the primocanesare able to grow unimpeded by the floricanes.Wait until the end of the second growing seasonbefore mowing plantings.

FIGURE 4. A simple “V” trellisdesign. Posts are set 30 fromvertical. This design does notlet you remove trellis wiresduring pruning.

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Pruning fall-bearing redraspberriesFall-bearing raspberries produce the fall crop onprimocanes—the current season’s growth. Formaximum yield, cut or mow off all canes at thesoil surface in late fall when plants are dormantor in early spring, before growth resumes. Usesharp tools or a heavy-duty mower with sharpblades to avoid damaging plant crowns.

The following spring, primocanes will begingrowing. These canes will produce fruit in earlyfall of the same season. Fruit will continue toripen until frost. In southern Wisconsin, you canoften extend the fall harvest into earlyNovember using sprinkler irrigation systems toprotect the fruit against frost damage.

This pruning technique offers many advantagesover other pruning practices. It’s less time con-suming to mow than to prune and it avoidsproblems with some common raspberry insectsand diseases. Additionally, damage from rabbitsfeeding on canes in winter and winter injury arenot a concern.

If you prefer to harvest two crops per year, followthe pruning techniques described for summer-bearing cultivars. Be aware, though, that manyof the better fall-fruiting cultivars are not winter-hardy, so the second crop will be lost if the canesdie back over winter.

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30

40

15

remove no more than25% of the cane

Dormant pruning. Head back canetips in early spring to keep canes frombecoming top heavy.

Summer pruning. Immediately after the last harvest,remove all but three or four of the sturdiest new canesper foot of row.

PRUNING SUMMER-BEARING RED RASPBERRIES

Percent offruit produced

You can harvest fall-bearing raspberries

5 to 15 days earlier than normal if you place

floating row covers over mowed plantings in

early spring. Loosely drape the cloth over

the row. To hold heat in, use soil or u-shaped

pins to seal the cloth edges around the base

of the planting. Remove the covers when

temperatures reach 80°F or when primocanes

are 12 to 18 inches tall.

HARVESTING CROPS EARLIER


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Pruning black and purpleraspberriesSummer pruning. Pinch out the tip of eachshoot when primocanes of black raspberries are24 inches high and when the canes of purpleraspberries are 30 inches tall. Each cane then willproduce several side branches. This makes thefruit easier to pick and increases production.Immediately after harvest, cut out at groundlevel and burn all the canes that bore fruit.

Dormant pruning. Before growth starts in thespring, select four or five sturdy canes per plantand remove and burn all others. Cut back theremaining side branches of black raspberries to12 inches and the side branches of purple rasp-berries to 18 inches. Secure the canes to a trellisor stake. Remove old fruiting canes at this time ifyou did not do so the previous summer.

Dormant pruning. Remove all but four or five of the sturdiest new canes.Cut back remaining side branches.

12" (black)18" (purple)

30" (purple)24" (black)

remove top2–3 inches

Summer pruning. Remove the top 2 to 3 inches when black raspberries are24 inches tall and purple raspberries reach 30 inches.

PRUNING BLACK & PURPLE RASPBERRIES

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INSECT MANAGEMENTGood cultural practices will usually reduce insectproblems, as healthy canes recover more rapidlyfrom insect attack. Some pests occasionallybecome too abundant, despite cultural practices.Temporary chemical control measures will beneeded. Certain insect pests will always be trou-blesome if there are many wild host plants nearthe patch.

For additional management guidelines, homegardeners should consult Extension publicationRaspberry Pest Management for Home Gardeners(A2128). Commercial growers should refer toExtension publication Strawberry and RaspberryPest Management for Wisconsin (A1934).

Raspberry cane maggotThis insect causes the cane tips to wilt or breakoff in late spring or early summer. The base ofthe wilted portion turns purple and the broken-off ends look like they were cut with a knife. Theadult cane maggot is a small, grayish fly abouttwo-thirds as large as a house fly. Flies appearshortly after spring growth begins and lay theireggs in new buds or in the tips of new shoots.The maggots or worms feed around the inside ofthe stem and completely girdle it. Maggots workdownward in the stem below the break point andremain there all winter.

To control, carefully examine the planting in Mayand June. If you see drooping cane tips, cut them

off several inches below the girdlepoint and burn. In late fall or winter

remove injured canes missed inthe early season examination.

You probably will not needchemical control as theseinsects rarely attack morethan a few shoots in a

planting.

Red-necked cane borerThe adult red-necked cane borer is a bluish-blackbeetle about 1⁄4-inch long. It appears on the canesin late May or June. The beetle’s “neck” is a dis-tinctive coppery-red color. It lays its eggs in thecane bark and the larvae bore beneath the bark.The boring causes the stem to swell 1⁄2 to 11⁄2inches in diameter, several inches along the cane.By late fall, the swellings contain creamy white-colored grubs up to 1⁄2-inch long.

To control, cut out and burn all canes with abnor-mal swellings during the fall and winter. If theproblem persists, you may need to apply a pre-bloom insecticide to the canes.

Raspberry crown borerThis insect causes the leaves toturn red prematurely and the caneto wilt in late summer. The boreris about 1-inch long with awhite body and brown head.It feeds in the larger roots, inthe crown, or at the base ofcanes. The adult moth looks likea yellow jacket wasp and appears late summer orearly fall. It lays eggs on the foliage, and the lar-vae crawl to the crown. They overwinter underthe bark just below the soil surface. In the spring,the larvae attack new cane buds and finally movedownward toward the crown. It takes them2 years to develop completely.

To control, dig and remove infested plants com-pletely, when possible. There are no insecticidesregistered for use against this pest in home plant-ings. For commercial plantings, an insecticidemay be used in problem patches. Apply as adrench around the base of each plant in earlyMay. Repeat the treatment for at least 2 years.

Raspberry cane borerWhen this insect lays its eggs, it makes a doublerow of punctures around the stem tip, causingthe cane tips to wilt. The adult female is a slen-der, black and yellow-striped beetle about 1⁄2-inch

long with very long antennae. Grubs bore downthe cane a few inches and hibernate for the win-ter. The following season, grubs bore downwardwithin the cane, killing it.

To control, remove wilted cane tips 5 to 6 inchesbelow the punctured area. Burn the prunings todestroy the insects inside.

Tree cricketsThese insects are not pests because of their feed-ing habits. Although some species will occasion-ally feed on leaves or ripe fruit, they also feed onother insects, fungi, and pollen. Indeed, they areoften considered beneficial because they prey oncertain types of slow-moving pests, such asaphids.

Tree crickets injure canes when adult females layeggs in the fall. They bore a series of tiny holes inthe cane and lay an egg in each hole. These holesare usually in a single row, spaced about 25 holesto the inch, and may extend 2 to 3 inches. Thecane often dies above the series of holes.

The insects pass the winter in the egg stagewithin the canes or in the twigs of other plants.In spring, the eggs hatch into slender, pale-greencrickets that grow slowly until they reach theadult stage in late summer. The adults are soft-bodied, pale-green insects, about 1-inch in lengthwith long slender legs and very long antennae.They are active primarily at night.

If these insects seriously injured canes in the past,examine canes in late fall to early spring for theegg-laying punctures. Prune out and burn punc-tured canes to destroy the overwintering eggs.

Japanese beetleThe Japanese beetle is a relativelyrecent invader of Wisconsin. It ismost serious in the southern partof the state, but extends into cen-tral Wisconsin, and will likely continue to be anincreasing problem. The 1⁄ 3-inch beetles are red-dish brown and metallic green, with a series ofwhite tufts of hair around the edge of the wingcovers. They feed on many types of trees andshrubs, especially from late June to early August.All members of the rose family, including rasp-berry and blackberry, are favorite food plants ofJapanese beetle. Populations can build to verylarge numbers, resulting in substantial damage tofruit and foliage. They are strong fliers and caninvade from considerable distances from outsidethe immediate garden area. Plants can toleratemodest defoliation (10 to 15%) but higher levelsof damage may reduce crop yield. On cane fruits,feeding damage can be to both leaves and fruit.

Many insecticides registered for use in raspberryplantings will kill Japanese beetle adults, but oth-ers may soon fly in from adjacent untreatedareas. Japanese beetle traps are available and cancatch thousands of beetles, but, because they canattract more beetles than they catch, research hasshown that the use of traps can actually increasedamage to small gardens. If you use traps, theyshould be placed at least 50 feet away fromplants you wish to protect. If your planting is rel-atively small, you may find success using thewoven fabric “floating row covers” that are avail-able to protect garden plants from flying insects.

Raspberry sawflyThis insect is probably Wisconsin’s most commonraspberry foliage pest. The spiny, pale wormsattack first when leaves are about three-fourthsgrown. They feed along the leaf edge, eatingirregular holes until only the leaf veins remain.Characteristically, the worms raise their head andtail when disturbed. The adult is a black waspwith yellow and reddish markings.

To control, apply an insecticide just before thefirst blossoms open.


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Spider mitesOccasionally, spider mites become troublesome,particularly during prolonged hot, dry weather.The minute creatures feed on the undersurface ofleaves causing the foliage to become spotted withwhite or brownish flecks. If mites are too abun-dant, leaves will begin to fall and fruit will dry up.

If mites persist, use a dormant spray for control.During the growing season, use a recommendedmiticide.

Raspberry fruitwormThe grub is slender, whitish andabout 1⁄4-inch long. It feeds insidebuds or in developing fruit, usu-ally causing the fruit to drop or decay before har-vest. Full-grown larvae drop to the ground,pupate, and emerge as beetles the following sea-son. Beetles are light brown, hairy, and about1⁄8-inch long. They feed on the tender foliage. Adultbeetles will partially skeletonize the leaves. Theylay their eggs on or near buds and green fruit.

To control, cultivate soil thoroughly in late summerto break up the pupal cases. If chemical control isnecessary, treat just before the first blossomsopen and again after the blossom period.

Picnic beetlesAlso called sap beetles, these small,black insects with reddish-yellowspots on their backs become a severenuisance soon after berries begin toripen. The beetles are attracted to alltypes of overripe fruit. They may become abun-dant if excessive food sources are available out-side the raspberry planting.

To control, remove as much damaged or overripefruit from the planting as possible. Frequentpicking will help reduce the amount of overripefruit and decrease the area’s attractiveness to thebeetles. If they become extremely abundant, youmay need an insecticide treatment to salvage thefruit. Insecticides are available to use during har-vest, interrupting it briefly.

DISEASE MANAGEMENTAnthracnose, spur blight, cane blight,Verticillium wilt, and gray mold are the moreimportant fungal diseases that affect raspberriesin Wisconsin. Powdery mildew occurs sporadi-cally and is not a serious problem in most years.Phytophthora root rot has been diagnosed in sev-eral locations in the state, and fire blight, causedby a bacterium, has been confirmed. Virus dis-eases are widespread in Wisconsin and may bethe limiting factor for raspberry production insome areas.

Accurate diagnosis of the problem is the first steptowards effective disease management.Consistent disease management is essential forlong-term raspberry production. It is bestachieved by an integrated approach, whichshould include planting resistant cultivars (whenknown and available) and using both chemicaland cultural control practices.

Cultural practices. Cultural practices that canbe effective in disease management are:

■ Plant only certified, pathogen-free plantsobtained from reliable nurseries. Be aware,however, that only a few pathogens arescreened at nurseries.

■ Destroy wild or abandoned brambles nearcommercial and garden plantings; these arelikely to be reservoirs for pathogens, especiallyviruses.

■ After harvest, remove and destroy canes thathave fruited or are weak and diseased; muchof the inoculum for the following season isproduced on canes infected during the currentseason.

■ Improve air circulation by proper thinning andpruning and by controlling weeds. This willreduce moisture levels and promote drying inthe plant canopy; most of the diseases causedby fungi need extended periods of wetness onthe plant surface for infection to occur.


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Chemical control. In addition to cultural prac-tices, chemical controls often are helpful to main-tain a high-quality raspberry planting. Only alimited number of fungicides are registered tocontrol the fungal diseases that affect raspberries.For specific information on fungicides and appli-cation schedules, consult Extension publicationsStrawberry and Raspberry Pest Management inWisconsin (A1934) or Raspberry Pest Managementfor Home Gardeners (A2128). Before establishing anew commercial raspberry planting, considerusing a preplant soil fumigant.

AnthracnoseThis fungal disease can attack all raspberries, butblack and purple cultivars are more susceptiblethan most red cultivars. Small, purplish spotsappear on the young canes and spurs. The spotsenlarge and become oval-shaped and slightlysunken with buff-colored centers and purple bor-ders. As heavily diseased canes mature, they dryout and crack lengthwise. With late-season infec-tions, the lesions are generally larger, more buffor gray than purple, and so numerous that theyjoin together and produce a condition known as“gray bark.” Diseased canes are prone to winterinjury. Dark-colored fruiting bodies develop in acircular pattern on diseased canes. On leaves,lesions are small, approximately 1⁄16 to 1⁄8 inch indiameter, irregularly shaped, and whitish-gray incolor with purple borders. Eventually the centersmay drop out of the lesions creating a “shot hole”appearance on the leaf. Although the fungus mayattack the fruit, rarely is this of any economicimportance.

To manage, follow the cultural controls and fun-gicide applications recommended above.

Spur blightThis is one of the most troublesome fungal dis-eases attacking red raspberries. It also can occuron purple raspberries but usually is not a prob-lem on black raspberries. Symptoms appear firston the green primocanes in late spring or earlysummer. Bluish-brown or purplish-browncankers develop on the canes, usually where a

leaf is attached and usually on thelower portion of the cane.Occasionally leaves become infected.Lesions on leaves are large, brown,and wedge-shaped. Diseased leavesmay fall off, leaving only the petiolesattached to the cane. Cankers oncanes enlarge but usually stop beforereaching the next bud in eitherdirection. When these diseasedcanes become fruiting canes thenext season, the side branchesgrowing from the cankered areas are weak andhave yellowish leaves. The canes remain purplishto dark brown until late summer or fall, whenthey turn grayish. The bark splits lengthwise andsmall, pimple-like fruiting bodies producingspores appear in cankers.

By autumn, larger black pustules appear in thesame areas. These are another type of fruitingbody (which produces a different type of spore)and may resemble the fruiting bodies of theanthracnose fungus in its “gray-bark” stage.However, the fruiting bodies of the spur blightfungus are scattered rather than arranged in a cir-cular pattern.

To manage, follow the cultural controls and fun-gicide applications recommended earlier.

Cane blightWith this fungal disease, cankers appear nearwounds or at the base of the canes, and sidebranches may suddenly wilt—typically whenberries are beginning to ripen. On the surface ofolder cankers, small black dots (fruiting bodies ofthe fungus) may appear. These dots are often sur-rounded by smoke-colored smudges of spores.

To manage this disease, both cultural controlsand fungicide applications are recommended (seesuggestions in Cultural Practices and ChemicalControls). Infection occurs through pruning andother types of wounds; therefore, avoid pruningand tipping during wet weather. Black raspber-ries appear to be more susceptible than red orpurple raspberries.

Verticillium wiltVerticillium wilt is caused by a soilborne fungusthat attacks the roots and vascular system ofraspberry and other plants. Symptoms are lesssevere on red raspberries than on black and pur-ple raspberries. Initial symptoms usually appearbetween late spring and early summer. Oninfected plants, lower leaves on some of the pri-mocanes will appear dull green rather than thetypical bright green of healthy plants. As the dis-ease progresses up the stem, the older leaves turnyellow and then drop off. The tip of the shootwill start to wilt, and eventually the entire canemay wither and die. Fruiting canes infected theprevious season are more likely to die than arenewly infected primocanes. Symptoms tend to bemore severe when temperatures are high and thesoil is dry.

A symptom called “blue stem” can occur on thecanes of many cultivars. This dark blue discol-oration appears as streaks or covers the entiresurface. In advanced stages of disease, the plant’svascular system is reddish in color and can beseen by cutting into an affected cane near itsbase. Often only one or two of the canes on aplant will show symptoms, and the remainingcanes appear unaffected.

To manage this disease, begin by planting in asite that has never had Verticillium wilt and hasnot been used to grow one of the other suscepti-ble hosts of this disease (e.g., tomato, potato, egg-plant, strawberry, and others). Purchase andplant only pathogen-free plants. Remove anddestroy symptomatic plants, including all theroots, as soon as they are recognized. If you mustplant in a site where Verticillium wilt hasoccurred previously, there are two options tohelp reduce potential problems: grow a crop notsusceptible to the disease (e.g., grain crops orcorn) for 3 to 4 years before planting raspberriesor consider using a preplant soil fumigant oncommercial plantings (see suggestions inChemical Controls). Fungicides will not controlthis disease.

Gray mold (Botrytis fruit rot) Gray mold is one of the most common flowerand fruit rots affecting raspberries. It is caused bya common fungus, and disease development isfavored by wet conditions between bloom andharvest. Young flowers may blacken and die,similar to the symptoms of fire blight. Infectedfruits develop areas of light brown cottonygrowth that later become powdery and gray asspores are produced. The disease may affect indi-vidual drupelets or the entire berry.

Proper site selection and thinning of canes topromote air circulation and drying conditions areimportant to manage gray mold. When environ-mental conditions favor disease, fungicidesshould be applied (see suggestions in ChemicalControls).

Powdery mildewPowdery mildew is a potential problem in anygiven year; however, it is rarely of economic con-cern in Wisconsin. Unlike most fungal diseases,powdery mildew does not require free water—high relative humidity is enough. Symptoms firstappear as light green blotches on the upper sidesof leaves with corresponding white patches ofspores on the undersides of leaves. Eventually, awhitish-gray powdery growth appears on, andmay cover, both sides of the leaf. On severelyaffected shoots, leaves become twisted andshoots are stunted. This white, powdery growthalso may cover the fruit.

To manage this disease, both cultural controlsand fungicide applications are recommended(see suggestions in Cultural Practices andChemical Controls).

Phytophthora root rotThis disease—caused by soilborne, water moldfungi—typically affects plants growing in soilwith poor drainage that is wet for extended peri-ods. Above ground, canes appear weak, stunted,and unhealthy, and leaves are small and off-color.Below ground, roots and the lower portion of thecane are rotted and typically reddish-brown.

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Feeder and lateral roots may be missing entirely.Plants usually decline over time and, in mostcases, eventually die. Occasionally, plants maycollapse and die suddenly.

To avoid Phytophthora root rot, plant raspberriesin well-drained soils. On soils with questionabledrainage, improve soil drainage or plant onraised beds. Fungicides effective against thesefungi are available, but they are not a substitutefor good cultural practices.

Fire blightFire blight is a serious disease affecting apple,pear, and other plants in the rose family.Although the disease on raspberry is caused bythe same bacterium that attacks apple and pear,the raspberry strains will not infect apple andpear, and the apple and pear strains will notinfect raspberry. Symptoms of the disease includeblackened shoot tips that wilt to form character-istic “shepherd’s crooks,” blighted flowers andblackened, immature fruits on dead stems.

Because of the relatively rare occurrence of fireblight on raspberry, no control strategies havebeen developed. Cultural practices aimed at dis-ease management, especially removal of diseasedcanes, may be beneficial (see suggestions inCultural Practices).

Crown and cane gallsThese two similar dis-eases are caused bytwo different butclosely related soil-borne bacteria. Canegall occurs most oftenon black and purple

raspberries and rarely on red raspberries. Crowngall occurs primarily on the lower stem or rootcrown of black raspberries, on the roots of redraspberries, and on both the root crown and rootsof purple raspberries. This disease is particularly

a problem in nurseries; therefore, examine plantscarefully before planting. Galls initially arespongy, rough, and wart-like; later they becomehard and woody. Both bacteria infect plants pri-marily through wounds; consequently, galls tendto occur where plants have been wounded orinjured.

Planting pathogen-free plants is the most impor-tant step in preventing these diseases. Avoidinjuring roots and crowns. Chemical controls arenot available.

MosaicMosaic is one of themost commonly occur-ring and widespreadvirus diseases affectingraspberries. It iscaused by severalviruses, acting alone orin various combina-tions. All of theseviruses are transmitted by aphids. Leaves onaffected plants can be mottled (light to darkgreen), blistered, or dwarfed. Infected foliagemay turn yellow. Berries may be small and fallapart easily. Plants become progressively morestunted and unproductive over time. In hotweather, foliage symptoms often disappear.

This disease can best be managed by plantingvirus-free canes and controlling aphids. If fewerthan 10% of the plants are affected, removing dis-eased plants (roguing) can be effective. If agreater proportion of the plants are affected,maintain the planting until fruit production is nolonger profitable, then destroy it. Do not estab-lish a new planting next to one with virus-infected plants or near wild bramble plants.

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Tomato ringspot virus (crumbly berry)Tomato ringspot virus may be the most wide-spread virus in raspberries in North America. Itis especially important in red raspberries. Thedisease is also known as “crumbly berry”because affected plants produce small mis-shapened berries that fall apart when picked.Eventually these plants become stunted andunproductive. Leaves on fruiting canes may turnbronze in color. The virus is transmitted by dag-ger nematodes and has a wide host range,including many weeds.

Good cultural practices are essential for virus dis-ease management. Before planting, have a repre-sentative soil sample analyzed for the presence ofdagger nematodes. If necessary in commercialplantings, fumigate soil. To help prevent spread-ing the disease, avoid moving soil, which maycontain virus-carrying nematodes, from areaswith symptomatic plants to areas where plantsshow no symptoms.

Leaf curlThis virus disease is less common than mosaic orcrumbly berry. Leaves curl downward andbecome dwarfed, and shoots appear stunted.Some shoot proliferation may develop. Aphidstransmit the virus that causes leaf curl. To man-age, follow the recommendations suggested formosaic.

WEED MANAGEMENTWeeds compete for water, nutrients, and lightduring critical periods of active growth andfruiting. They can also harbor diseases andinsect pests, and can interfere with cultural prac-tices and harvesting. To minimize weed prob-lems, you’ll need to use a combination of timelycultivation, mulches, and appropriate herbicides.

Control severe infestations of perennial weeds,such as quackgrass or Canada thistle, before set-ting out new raspberry plants. Usually repeated

cultivation plus a selective, nonresidual herbi-cides will effectively control weeds in one fullgrowing season before planting. Before using anyherbicide in a preplant weed control program,check current Extension service information onherbicide persistence and potential toxicity tocultivated crops.

Cultivate raspberries frequently after planting toprevent weed growth and seeding. In establishedplantings, stop cultivating by mid-August orbefore harvest to avoid damaging ripening fruitand to allow plants to “harden off” early in fall.To reduce injury to raspberry plant roots, nevercultivate deeper than 2 to 3 inches.

Plant a cover crop such as grass in the areabetween rows and keep it mowed. The covercrop will help keep weeds out of the planting.Non-spreading grasses such as perennial ryework best.

Suggestions for using herbicides in establishedraspberries are revised frequently. For currentsuggestions refer to Extension publicationRaspberry Pest Management for Home Gardeners(A2128), or for commercial plantings consultStrawberry and Raspberry Pest Management inWisconsin (A1934). These bulletins are availablefrom your county Extension office.

PROBLEM SOLVING

Why raspberry plants fail to bearThere are many potential reasons why raspber-ries don’t bear fruit—cold winters, too much fer-tilizer, crowding, pests, or incorrect management.This section describes the most common prob-lems and how to avoid them.

Cold injury. Raspberries are susceptible to win-ter cold injury. Fully acclimated red raspberriescan tolerate temperatures to about –20°F, purpleraspberries to –10°F, and black raspberries to –5°F.Below these temperatures injury and crop lossare certain, although injury may occur at warmertemperatures. Mulching helps keep the crowntemperatures stable and will protect the crown,


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particularly in sandy soils. In areas where snowis deep and reliable so that the canes are covered,winter injury should be minimal.

Overfertilization. Raspberries require moderatenitrogen fertilization. Bearing plantings shouldonly receive two light applications of nitrogenfertilizer in the spring. Heavy nitrogen fertiliza-tion encourages vegetative growth at the expenseof fruit growth. Young plantings should be wellfertilized to encourage suckering.

Overcrowding. Because raspberries sucker pro-fusely, plantings may become too dense.Overcrowding occurs when too many canes areallowed to grow in a section of row. The caneswill compete with each other for light, water, andnutrients. When raspberry patches become asolid mat rather than a collection of rows, fruitquality declines, and harvest is difficult.

Pests. Weeds will compete with raspberries forwater and nutrients. Grass weeds are most com-petitive. Weedy berry patches will produce fewfruit of poor quality. Dense weeds also promoteslow drying, make spray penetration difficult andimpede harvest. Insects such as raspberry sawflycan reduce leaf area leading to canes having toolittle carbohydrates to produce flower buds.

Incorrect management. Summer-bearing andfall-bearing raspberries must be managed cor-rectly to yield fruit. The canes of summer-bearingraspberries do not produce flowers and fruit untilthe second year. If summer-bearing raspberriesare mowed off each dormant season (as is typi-cally done for fall-bearing raspberries), no flori-canes will be left to produce the crop.

Poor fruit qualityIn some instances raspberry plantings producefruit, but the fruit are small, crumbly, poorly col-ored and of low quality. This section describesseveral problems that lead to poor fruit quality.

Heat and light. In hot summers raspberrieswill sometimes become “crumbly” where theindividual drupelets are not well connected. Thismay also be caused by viruses. When fruit are

exposed to direct sunlight the fruit can “scald”resulting in either a few white drupelets or fruitthat are dried out on one side. Often these condi-tions are found in patches with weak cane andfoliage growth such that leaves don’t shade thedeveloping fruit. Keeping patches well pruned,irrigated and fertilized will help prevent theseproblems.

Age. As plantings age yields decline. Raspberryplantings are usually kept to bear fruit between10 and 12 years. After that the planting should beremoved and another crop rotated into that spacefor a year or two before replanting. Old plantingsusually have more weed and insect pests thanyounger plantings.

Insufficient pruning. Plantings rapidly becomeovercrowded unless they’re pruned annually.When hedgerows or hills become too wide, littlefruit of poor quality will be produced in the inte-rior of the canopy. Remove floricanes after the fruithas been harvested. During the dormant seasoncut out all but four to six canes per foot of row.

Neglected plantings. Fruit quality sufferswhen plantings are not cared for. The plants needto receive proper cultivation, fertilization, andpest management as described in this bulletin.Reclaiming neglected plantings is usually noteffective. It is better to remove the planting andstart over with new nursery stock.

Poor growing conditions. Patches establishedin poor sites will produce poor fruit. Wet, shady,or droughty sites will result in poor plant growthand few small fruit. Raspberries must have atleast a half day of full sun to be productive. Thesoil should also be prepared properly beforeplanting.

Pests. The most common insect pest of raspber-ries is the picnic beetle. Picnic beetles feed on ripefruit remaining on the canes. The beetles feedand crawl into the “thimble” interior and are notalways visible until harvesting the berries.Harvesting fruit two to three times per week willhelp keep feeding to a minimum. In severe casesinsecticides will be required to manage picnicbeetles.

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Inferior cultivars. Inferior cultivars will pro-duce inferior fruit. For the best chance of successplant cultivars recommended in this bulletin, inHome Fruit Cultivars for Northern Wisconsin(A2488), or in Home Fruit Cultivars for SouthernWisconsin (A2582).

Why plantings failPlant death is usually caused by a number ofinteracting factors rather than by a single identifi-able cause. One injury may provide sufficientstress to allow other problems to eventually killthe plants. Several reasons for plant death aredescribed here.

Winter injury. Red raspberries are sufficientlyhardy to survive and fruit in Wisconsin’s harshclimate. However, purple and black raspberriesare quite winter tender and will often sustainwinter injury. Snow can be captured over rasp-berry plants during the winter by placing snowfencing to the windward side of the plants. Snowwill insulate the canes and protect them from thecoldest temperatures.

Too much water. Raspberry plants will not tol-erate wet feet. Saturated soils do not allow air toreach the roots and they predispose the plants toroot rot diseases. Plant raspberries only in well-drained soils. Heavy clay soils will remain wetlonger than lighter sandy soils. Use irrigationprudently so soils don’t remain wet.

Drought. Raspberry plants are shallow rootedand don’t explore a large soil volume. When soilsdry out the plants will wilt and die. Weeds willalso compete with raspberry plants for moisturewhen water is in short supply. Light sandy soilsare particularly prone to drought. Addingorganic matter, controlling weeds, and irrigatingwill keep soils moist.

Mechanical injury. A myriad of factors caninjure raspberry plants. Common sources ofmechanical injury include lack of care while pick-ing, running mowers too close to the canes, andanimal feeding and browsing. If deer populationsare high the planting may need to be fenced todeter the deer.

Insect and disease pests. Severe infestationsof insects or diseases can weaken plants makingthem prone to winter injury or summer droughts.While these pests seldom kill plants outright,they are often contributing factors. If your plant-ing becomes infected with viruses the only solu-tion is to remove the planting and replace it withfresh plant material. Manage insect and diseasepests using the practices described earlier in thispublication.

RELATED PUBLICATIONS

For home gardenersFertilizing Small Fruits in the Home Garden

(A2307)

Home Fruit Cultivars for Northern Wisconsin(A2488)

Home Fruit Cultivars for Southern Wisconsin(A2582)

Raspberry Pest Management for HomeGardeners (A2128)

Raspberry Disorders:■ Cane Blight and Spur Blight (A3236)■ Fire Blight (A3499)

Small Fruits: Insect and Disease Management forBackyard Fruit Growers in the Midwest(AIDEA2), Iowa State University, (515) 294-8802

For commercial growersStrawberry and Raspberry Pest Management in

Wisconsin (A1934)

Compendium of Raspberry and BlackberryDiseases and Insects, APS Press, (800) 328-7560.

Midwest Small Fruit Pest ManagementHandbook (Bulletin 861), The Ohio StateUniversity, (614) 292-1607.

Bramble Production Guide (NRAES 35), CornellUniversity, (607) 255-7654

Copyright © 2007 by the Board of Regents of the University of Wisconsin System doing business as thedivision of Cooperative Extension of the University of Wisconsin-Extension. Send inquiries about copyrightpermission to: Manager, Cooperative Extension Publishing, 432 N. Lake St., Rm. 103, Madison, WI 53706.

Authors: B.R. Smith is professor of horticulture, College of Agriculture, Food and EnvironmentalSciences, University of Wisconsin-River Falls and University of Wisconsin-Extension, CooperativeExtension. T.R. Roper is professor of horticulture, D.L. Mahr is professor of entomology, and P.S.McManus is professor of plant pathology, College of Agricultural and Life Sciences, University ofWisconsin-Madison and University of Wisconsin-Extension, Cooperative Extension. Produced byCooperative Extension Publishing. Cover illustration by Catherine Baer, copyright 1998. Japanese beetleillustration by David Shetlar.

University of Wisconsin-Extension, Cooperative Extension, in cooperation with the U.S.Department of Agriculture and Wisconsin counties, publishes this information to further the purpose ofthe May 8 and June 30, 1914 Acts of Congress; and provides equal opportunities and affirmative action inemployment and programming. If you need this material in an alternative format, contact the Office ofEqual Opportunity and Diversity Programs or call Cooperative Extension Publishing at (608) 262-2655.

This publication is available from your Wisconsin county Extension office or from CooperativeExtension Publishing. To order, call toll-free 877-WIS-PUBS (947-7827) or visit learningstore.uwex.edu.

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