1

2

To be successful, peanut seedproducers must understand seedquality, know how seed quality isachieved and lost, and under-stand how they can ensuredelivery of high-quality peanutseeds to farmers.

In many respects, the productionof peanuts for seed is similar tothe production of peanuts forcommercial use. With fewexceptions, the requirements fordisease management, soil amend-ments, and crop handling areessentially the same, regardless ofthe intended use of the har-vested crop. Like commercialpeanut producers, peanut seedproducers seek most of all tomaximize yield. But because ofthe specialized use of the seedcrop, seed growers must givecertain production practicesmore attention to enhance seedquality. This is particularly truewhen considering disease man-agement, gypsum application,digging, and curing. In addition,seed growers must follow prac-tices that ensure genetic and

Peanut ProductionA Guide for Producers of Virginia-Type Peanut Seed

P U R ETo keep seedlots GENETICALLY

• Keep accurate field records.

• Keep seed fields isolated.

• Thoroughly clean trucks,planters, diggers, and com-bines before changing varieties.

crop purity, must handle the cropcarefully to avoid quality loss,and must store the seeds in anenvironment that minimizesdeterioration of quality.

S E E D L O T Q U A L I T Y

Seed quality can be divided intofive separate, but related compo-nents: genetic purity, crop purity,health, germination, and vigor.Each is important, and each canbe affected by managementdecisions throughout the grow-ing season and during digging,harvest, curing, conditioning,and storage.

Genetic purityThe genetic composition of apeanut variety dictates maturitydate, disease and insect resistance,peanut quality (appearance aswell as protein and oil composi-tion), grade, and many othercharacteristics. Preserving thegenetic integrity of the seed cropis essential and is simply a matterof keeping accurate records,keeping equipment clean, and

exercising care when handlingthe seed.

Crop purityCrop purity refers to the presenceof contaminants, including weedseed, nutsedge tubers, other cropseed, and inert matter. Weed seedcontamination is not a majorconcern for peanut seed produc-ers. Growers should keep in mind,however, that keeping weeds outof the field in the first place isusually easier than removing weedseeds from the seedlot. Of greaterimportance is the presence ofnutsedge tubers, which can bedifficult to remove from shelledpeanut seeds.

Inert matter includes pods,stems, small stones, skins, andpieces of broken seeds. It isimportant to harvest peanuts atthe correct moisture and at thecorrect combine settings to reducethe amount of trash and brokenkernels collected.

Seed healthSeed health is related toseedborne diseases present on orin peanut seeds. Because peanutpods develop underground, theyare in constant contact withsoilborne pathogens. Somepathogens find their way intothe pods and infect the develop-ing seed.

Seedborne diseases are aconcern for two reasons. One isthe drop in germination causedby pathogens such as fungi.These pathogens are commonlyfound on peanut seeds andreduce germination by causingseed and seedling rots. However,

• Clean curing wagons, storagebins, augers, and conveyersafter each use.

• Clearly identify each bin withthe variety name and grower.

3

growers need not be overlyconcerned about these diseasesbecause peanut seeds sold in theVirginia-Carolina area are coatedwith a variety of chemicaltreatments before planting thateither kill seed pathogens orprotect the growing seedling longenough for it to become estab-lished. Do not plant untreatedseed. A list of effective seedtreatments can be found in theNorth Carolina Agricultural Chemi-cals Manual.

A second, more serious con-cern associated with seedbornefungi is the transmissionthrough seed stock of suchdiseases as Cylindrocladiumparasiticum (CBR). To develop abetter understanding of thesignificance of seed transmissionof CBR, it is important to em-phasize that under some circum-stances there may be no seedtransmission of the disease. Thisis true if 1) the seeds are pro-duced in clean fields, 2) infestedseeds are identified and discardedat the shelling plant, 3) thefungus dies during drying,storage, or following seed treat-ment, or 4) unfavorable fieldconditions during that seasonprevent the disease from form-ing.

Seed transmission of CBR canoccur. A survey of 62 commercialseedlots produced in 1997, whichwere sampled after conditioningbut before the application ofseed treatment, showed that anaverage of 1.3 percent (a range of0 to 5.6 percent) of the seeds hadspeckles, which signal the pres-ence of CBR. The speckles are theresting structures (sclerotia) ofthe fungus C. parasiticum and arehow it is transmitted from seedto fields. Speckled seeds werefound in at least one subsampleof every seedlot. While all speck-led seed had viable C. parasiticumat harvest, by planting time only

• Properly adjust combines to reducedamage to pods and kernels.

• Cure peanuts slowly, and avoidexcessive heat.

• Handle seeds carefully duringconditioning.

P U R ETo keep seedlots

• Keep seed fields clean and freeof weeds.

• Thoroughly clean diggers,combines, trucks, augers,conveyers, and storage bins.

P H Y S I C A L L Y

4 to 5 percent of the speckled seedretained the fungus. This meansthat most of sclerotia died duringwinter seed storage.

To improve our ability to studyCBR transmission via seeds,hand-picked, speckled seeds wereselected from a commercialshelling operation followingconditioning and sorting butbefore the addition of seedtreatment. Our field studiesshowed that at least some diseasewas transmitted every year ifspeckled seeds were plantedwithout seed treatment. Seedtreatment cut the transmissionrate about in half, and transmis-sion occurred in only 2 of 4 years.Based on our surveys and theresults of our field studies, wecalculated that from 0 to 60plants per acre can be infected asa result of planting speckled seed.

To avoid seed transmission ofpeanut diseases, grow peanutsproduced for seed in fields withno CBR. Keep fields on long croprotations, fumigate them beforeplanting, and scout late in theseason to identify these diseases.Harvest only those portions ofthe field that are free from thedisease. No other disease at thistime is known to be transmittedon peanut seed at levels highenough to cause concern. Tomato

spotted wilt virus (TSWV) is nottransmitted by seed.

GerminationGermination is the measure of aseed’s ability to produce a normalseedling when planted in idealconditions (optimal temperatureand moisture plus good aera-tion). It is this value that isreported on the seed tag and isone of the criteria used to deter-mine if the seedlot meets StateSeed Law requirements for sale. Itis also the value that farmersoften use to calculate yearlyseeding rates.

Field conditions are rarelyideal, and the germination testcan at times overestimate fieldemergence. Regardless of itslimitations, the seed germinationtest is the universal standardmeasure of seed quality.

Freshly harvested peanut seedsare frequently dormant, meaningthe seeds will not germinate evenif conditions are favorable.Dormancy is a survival mecha-nism that prevents seeds fromgerminating at the wrong time.The environment during seeddevelopment can influence thelevel of dormancy. Often seedsproduced in hot, dry years willhave a “deeper” dormancy, which

4

means dormancy is harder tobreak during seed-germinationtesting. Usually, peanut seeddormancy disappears about 4months after harvest.

All state seed-testing laborato-ries follow specific procedures, asoutlined in the Rules for TestingSeeds by the Association ofOfficial Seed Analysts (AOSA).The Rules have specific germina-tion test guidelines and offerseveral options for breakingpeanut dormancy; each providesan accurate evaluation of germi-nation potential. If a seedlot-label shows a germinationpercentage that is much higherthan the official regulatorysample, the explanation may bethat the seeds in question werelabeled based on tests or evalua-tion criteria that did not followAOSA Rules. In such cases, a“stop sale” may be issued on thesuspect seedlot. It is, therefore,important that peanut seedsmenuse germination-testing laborato-ries that follow AOSA procedures.

Seed vigorPeanut seedlots with nearlyidentical germination percentages,planted in nearly identical fieldconditions, still may have verydifferent emergence rates andfinal plant stands. This variationin field performance can beattributed to differences in seedvigor. Vigor is the componentthat determines the potential forrapid and uniform emergenceunder a wide range of fieldconditions. No seed, no matterhow vigorous, can withstandprolonged periods of adverseconditions at planting. However,a high-vigor seedlot can with-stand stress during germinationand early seedling developmentlonger than a low-vigor seedlot.Stress could include cool, wet soils;crusting; chemical damage;

flooding; or any other environ-mental condition that places theseed in less than favorable condi-tions. Low-vigor seeds exhibitmany symptoms of deterioration,with delayed germination andemergence among the first notice-able signs, followed by a slowerrate of seedling growth and lessstress tolerance.

The key to attaining andmaintaining excellent germina-tion and vigor potential lies intiming and attention to detail. Inaddition to traditional produc-tion practices of fertilizing andpest management, good seedquality comes from properdigging, combining, and curingof the seed crop. The impact onquality of these practices isdiscussed below.

P R E - P L A N T A N DP L A N T I N G D E C I S I O N S

Seed selectionMost peanuts grown for seed inNorth Carolina and Virginia aregrown as a class of Certified Seed.For seed to be eligible for certifica-tion, they must meet field andseed standards established by theNorth Carolina or Virginia CropImprovement Associations.Consult these organizations forspecific requirements about grower

eligibility and to arrange for fieldinspections.

Field selectionAttention to field history andcrop rotation is the most efficientway to manage diseases, insects,and weeds. Select fields that donot have a history of soilbornediseases, such as stem rot andCBR. If soil diseases are severe,treat according to recommenda-tions found in the North CarolinaAgricultural Chemicals Manual andPeanut Information, AG-331. Longcrop rotations and use of culturalpractices can reduce the impact ofsoilborne diseases. If diseases aresevere, report the situation toyour seedsman.

Equipment tune-upOne way to maximize plantingefficiency is to tune your planter.Studies have shown that somepests, thrips in particular, are bestmanaged if plants are spaceduniformly across the field. Thereis also less TSWV with high plantpopulations and uniformplantings. Tuning the planterbefore the first trip to the fieldcan help you achieve uniformseed spacing and planting depth,reduce damage to the plantedseed, and minimize down timeduring the growing season.

Table 1. Gypsum sources and application rates.

Application Rate (pounds per acre)

CaSO4* Band Broadcast

Source % (16-18 inches)

USG Ben Franklin 85 600 —USG 420 Granular 85 — 1,200USG 500 70 — 1,300JTM peanut maker 72 — 1,300TG Phosphogypsum 50 — 2,000

* Guaranteed analysis percentage in registration with N.C. Department of Agricultureand Consumer Services.

5

G R O W I N G S E A S O N

Gypsum applicationCalcium is a critical element inpeanut seed development. It isimportant in the formation ofcell walls, in cell function, and intissue formation; and it is essen-tial for the germination processes.Seedlings produced from seedswith a calcium deficiency exhibitseveral symptoms, includingwatery hypocotyls (also known ashypocotyl collar rot) and deformedplumules.

Several reports have indicatedthat the large, Virginia-typepeanut seeds need at least 450parts per million of calciumwithin the seed for rapid, normalgermination. Few North Carolinaand Virginia soils containenough residual calcium to allowgrowers to skip application ofthis critical element. Seed fieldsrequire annual applications ofgypsum at the right time and inthe correct amount. Late June orearly July at early bloom is the

optimal time, and rates dependon the source (Table 1).

Calcium uptake by the plant isclosely related to rainfall, andseeds produced in dry years oftenexhibit calcium deficiency (Table2). If seed fields are moisture-stressed during the growingseason, evaluate germination and

calcium-deficiency symptomsbefore co-mingling this productionwith seed from other fields. If seedquality is low, sell these seeds forcommercial use, not for seed.

BoronBoron is another element that iscritical for sound seed formationand germination. Boron defi-ciency is often seen at the base ofthe plumule where tissues appeardark. Another sign of deficiencyis a condition known as “hollowheart,” in which the center of thecotyledons appear sunken. Boroncan be added pre-plant withherbicide programs, as a compo-nent of fertilizers applied to thecrop, or as a foliar application inearly July. However, on sandy soils,heavy rains can leach pre-plantboron from the peanut plant rootzones. In this situation, foliarapplication may be the best.

D I G G I N G A N D H A R V E S T

Peanuts are indeterminate ingrowth habit. Therefore, atharvest, seeds on a single plant willbe at differing levels of maturity.Seed growers usually report bettergermination if their seed fields areharvested about 7 days earlier thancommercial fields. The decrease ingermination observed with laterharvests could be related to theenvironment during seed develop-ment, deterioration of pods with a

corresponding increase in me-chanical damage, or an increase inseed pathogens.

Research at North CarolinaState University supports growerobservations that germination candecrease if harvest is delayedbeyond an optimum digging date(Table 3). However, keep in mindthat varieties do respond differ-ently and that growing conditionscan dramatically affect seeddevelopment and consequentlyinfluence optimum digging date.N.C. Cooperative Extension Servicewill continue to evaluate newvarieties as they are released todetermine the optimum harvestdate for yield and seed quality.Seed growers should consult theircounty Extension center forinformation about how newvarieties perform in their area.

Studies have shown thatimmature seeds of many crops arecapable of germinating, and thisis also true of peanuts. However,germination of immature peanutseeds can be slow, seed vigoroften may be low, and seedlingsurvival could be in jeopardy.Thus, seed growers should avoidharvesting too early.

But how early is too early?In a three-year study, germina-

tion and vigor (as measured by cellleakage) were evaluated in NC 7and NC 9 seeds at different matu-rity levels (Table 4). Cell leakage isgenerally considered a reliable

Table 2. Influence of gypsum

and rainfall on seed calcium.

Seed Calcium (ppm)

Gypsum Adequate Inadequate

Lb/A Rainfall Rainfall

0 682 275200 725 343400 848 489600 919 469800 943 498

Table 3. Influence of harvest date (three-year average) on peanut seed

germination for four varieties.

Approximate Harvest Date

9/21 9/28 10/5 10/12

Variety % Germination

AT VC 1 86 90 88 88NC 7 81 82 87 76NC 9 79 84 88 76NC -V11 84 80 85 84

6

Table 5. Germination at various

levels of maturity of NC 9 peanut

seeds grown in 1990 and 1992.

Germination %

1990 1992

Yellow 90 60Orange 92 83Brown 92 96Black 91 100

* Maturity was based on pod mesocarpcolor using the hull scrape method.Yellow pods were about 40 percentmature, orange pods 60 percentmature, brown pods 95 percentmature, and black pods fully mature.

Maturity

Level*

Table 4. How cell leakage affects maturity.

Three-year average (1990, 1991, 1992) of germination and vigor (cell leakage) of

NC 7 and NC 9 seeds taken from pods at various levels of maturity.

Germination % Cell Leakage µmhos/cm/gram

NC 7

Yellow 80 88Orange 92 41Brown 94 23Black 98 14

NC 9

Yellow 75 76Orange 89 43Brown 95 28Black 96 18

* Maturity was based on pod mesocarp color using the hull scrape method. Yellow pods wereabout 40 percent mature, orange pods 60 percent mature, brown pods 95 percentmature, and black pods fully mature.

Maturity Level*

measure of seed vigor. The morethe cells leak, the more food islost (food that is needed for earlyseedling growth), and the lowerthe seed vigor. The lowest level ofseed leakage (the highest vigor) inour study was found in matureseeds (Table 4). High percentagesof germination did occur withseeds taken from immature yellowpods, but on the average, consis-tently better germination wasfound when seeds were nearermaturity (brown pod) or when

seeds reached maturity (black pod).Seed growers must understand

that harvesting too early maydecrease seed value, particularly inyears when the seed is grownunder stressful conditions. In1992, for instance, when condi-tions were wet and cool duringmuch of the seed developmentperiod, NC 9 peanuts producedseeds that germinated verypoorly when seeds were immature(Table 5). Acceptable levels ofgermination were obtained onlywith mature seeds. By contrast, in

1990, when conditions were closeto ideal, even immature seedshad high germination. There is adefinite correlation between theenvironment during seed devel-opment and seed quality ofimmature seeds.

Just as harvesting too early canmar the quality of seed peanuts,so can harvesting too late. Lateharvest means deterioration ofthe pod, more mechanical dam-age to the seed, increased seedpathogens, and potential frostdamage. A good rule of thumb isto harvest seed fields when most(at least 70 percent) of the seedsare close to or at maturity. Usingthe hull scrape estimation ofmaturity, this would correspondto harvesting when a majority ofpods are in the brown and earlyblack stages. (Be sure to evaluateeach seed field separately.)

Big seeds versus small seedsPeanut farmers and seed growersoften confuse seed size with seedquality. Many think the biggerthe seed, the better the seed.Others feel that smaller seedsgerminate faster and are thereforebetter than larger seeds. While itis true that seed size can influencespeed of germination, one mustbe careful to keep seed size in itsproper perspective.

• Dig when most of the pods and seeds are close to or at physiologicalmaturity.

• Combine as soon as average seed moisture is 20 to 25 percent.

• Avoid combining wet vines.

• Adjust combine often during the day.

• Go slowly enough to avoid mechanical damage.

D I G G I N G

C O M B I N I N G&

7

Consider this: For the germina-tion process to begin, seed mois-ture must be around 40 percent. Alarge seed that weighs 1 gram musttake up about 0.6 milliliter of waterto begin the germination process.A smaller seed of the same qualityweighing only 0.8 gram wouldneed to absorb only 0.4 milliliterbefore germination could begin.The larger seed will therefore takelonger to begin germinating,perhaps as much as 24 hourslonger, if moisture at planting isnot limiting. If moisture is limit-ing, it may take several days longerfor the larger seed to germinate. Itdoes not mean that the large seedis inferior in quality. It just takes alittle longer to hydrate.

Small seeds are often equatedwith immaturity in indeterminatecrops like peanuts. And while it istrue that immature seeds tend tobe smaller than mature seeds, onecannot assume that discardingthe small seed fraction willautomatically remove all theimmature seeds from the seedlot.A study showed that immatureseeds can be found in the largeseed portion of the seedlot andthat regardless of seed size,maturity is the factor thatdictates quality (Table 6). Notethat VA-C 92R peanut seedsresponded differently in 1993 and1994. The growing season in 1993

was very dry, and the seed qualityof immature seeds (yellow,orange, and brown pods) wasvery low, regardless of seed size.Seed produced in 1994 developedwith little or no stress during thegrowing season, and germinationwas much higher.

Digging and combiningOnce peanuts are dug, inverted,and left on top of the soil,environmental elements willinfluence seed quality. Whenpeanuts are dug, the moisture

Table 6. Percent germination at various levels of maturity and screen

sizes of VA-C 92R peanuts harvested in 1993 and 1994.

Screen Size

18 20 22 24

Maturity Level % Germination

1993

Yellow 23 30 38 —Orange 30 32 41 52Brown 38 40 54 52Black — 84 84 88

1994

Yellow 70 77 — —Orange 77 88 90 —Brown 96 98 96 99Black 95 100 99 100

content of seeds is still fairlyhigh. Seeds from yellow pods(immature) can have as much as60 percent moisture, while seedsfrom black pods (mature) usuallyrange from 35 to 40 percentmoisture. If temperatures shortlyafter digging reach 90OF orgreater, seeds can suffer physi-ological heat damage that canreduce germination and vigor. Iftemperatures drop below freezingshortly after digging and if seedmoisture is still above 35 percent,the water inside the seed’s cellscan freeze, also causing celldamage. Usually, once seedmoisture drops below 35 percent,freezing temperatures have littleeffect on seed quality.

Excessive rainfall after diggingcan delay combining. Generally,the longer the delay once peanutshave reached safe harvest mois-ture, the greater the chance ofdamage to seed quality. However,combining too soon after diggingalso can harm seed quality. Wetvines are tough, which makesharvesting difficult. Growersoften become too aggressive incombining wet vines, and rough

• Clean the peanuts before placing them in the curing wagon.

• Level the peanuts in the wagon.

• Dry slowly and with as little heat as possible. Heat air no more than15OF above ambient temperature.

• Turn dryers off when the average seed moisture reaches 10 percent.

• Do not store peanuts in the curing wagons.

E F F E C T I V EU R I N GC

Prepared by

J. F. Spears, Extension Seed Specialist, Crop Science

D. L. Jordan, Extension Peanut Specialist, Crop Science

J. E. Bailey, Extension Plant Pathology Specialist, Crop Science

500 copies of this public document were printed at a cost of $1,470.00, or $2.94 per copy.

Published by

NORTH CAROLINA COOPERATIVE EXTENSION SERVICE

Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Employment andprogram opportunities are offered to all people regardless of race, color, national origin, sex, age,or disability. North Carolina State University, North Carolina A&T State University, U.S. Departmentof Agriculture, and local governments cooperating.

05/02—500—JL/VG AG-622 E02-39003

• The seed crop has priority.

• Keep seed fields and harvested seed genetically pure and weed free.

• Avoid using fields with CBR as seed stock.

• Tune up planting equipment to ensure uniform stands.

• Apply calcium in the correct amount and at the right time.

• Dig peanuts when a majority of the pods are close to maturity.

• Combine as soon as seed moisture reaches 25 percent.

• Cure seed peanuts slowly.

S E E D G R O W E R STips for

handling of this sort can break orbruise the peanut kernels. A goodrule of thumb is to harvest peanutsas soon as possible after seedmoisture reaches 20 to 25 percent.

P O S T H A R V E S TH A N D L I N G O F S E E D S

CuringPeanuts should be cleaned beforebeing placed in the curing wagons.Removing dirt and trash maxi-mizes air flow, which reducesdrying time and costs. Curing ismost efficient and effective ifpeanuts are leveled in the trailer.

Seeds can be damaged byoverdrying, rapid drying, ordrying at high temperatures.Detailed techniques for curing arediscussed in Peanut Information,AG-331. Producers should takeparticular care when curing theseed crop because high-qualityseed can deteriorate rapidlythrough improper curing.

Seed storageOnce cured, peanut seeds shouldbe stored in a cool, dry environ-ment until delivered to theconditioning plant. Even shortperiods of poor storage condi-tions can lower seed quality.

Seed peanuts can be shelledsoon after harvest and stored inbulk containers. Again, it iscritical to keep seeds dry, cool, andwell aerated for quality to bemaintained. Airflow should beprovided around peanuts toensure continuous exchange of airin the storage area. Use fans tomove cool, dry air into the storagearea, particularly in warehousecorners where the flow is blocked.

S U M M A R YProduction of high-qualitypeanut seeds requires a high levelof management that beginsbefore planting and continues

through delivery of seeds to thepeanut farmer. Growers mustplan all farm operations well inadvance to ensure the seed crophas the highest priority. Lastly,

producers also must keep twofactors in the forefront of alldecisions about their crop—namely, disease management andmaturity at harvest.

Never store seedin curing wagons.

In memory of

JACK BAILEY

ËËË

ËËË