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AVRDC - The World Vegetable Center P.O. Box 42, Shanhua; Taiwan 74151tel: (886-6) 583-7801 fax: (886-6) 583-0009 email: info@worldveg.org web: avrdc.org

Suggested Cultural Practicesfor Sweet Pepper

by T.G. Berke, L.L. Black, R.A. Morris, N.S. Talekar, and J.F. Wang

Climate and soil requirements

Sweet peppers grow best between 21 and 24°C.When temperatures fall below 18°C or exceed 27°Cfor extended periods, growth and yield are usuallydecreased. Sweet peppers can tolerate daytimetemperatures over 30°C, as long as night tempera-tures are within 21–24°C. Sweet peppers are pho-toperiod and humidity-insensitive (daylength andrelative humidity do not affect flowering or fruit set).Sweet pepper grows best in a loam or silty-loamsoil with good water-holding capacity. But they cangrow on many soil types, as long as the soil is welldrained. Soil pH should be between 5.5 and 6.8.

Choosing a variety

Sweet pepper yields vary widely depending on va-riety. So begin by comparing the yield potential ofcurrently grown varieties with the yield potential ofthe best new varieties. Make sure, however, thatthe test plots were handled the way you intend togrow your crop.

Compare the total agronomic package. On claysoils, for instance, Phytophthora blight might bemore limiting that potato virus Y (PVY), so a PVY-resistant variety lacking blight resistance would likelybe a poor choice.

The following suggestions were developed forthe specific conditions at AVRDC in the Tai-wan lowlands (latitude 23° 7’ N, elevation 8 mabove sea level). Growers should adjust thesepractices to fit their local environment.

Growing peppers in a different season or undera different rotation system might provide higheryields and/or higher prices. Relay or intercroppingmight provide extra income from the same piece ofland, and reduce insect and disease problems.Calculate potential returns, and choose the varietyand cropping system that serve you best.

Seed treatment

The primary seed-borne fungal pathogens areColletotrichum spp., the causal agents of anthra-cnose. To minimize seed transmission, soak seedsin warm water (50°C) for 30 min or soak them in1.25% (v/v) Clorox for 30 min, and rinse in cold wa-ter. Apply a fungicide seed coating, such as 1 g ofBenomyl 20% active ingredient (AI) wettable pow-der (WP) and 1 g Thiram 20% AI WP (or 0.8 g ofBenlate [a mixture of Benomyl and Thiram] 50% AIWP) in 400 ml of water, so that the final concentra-tion is 0.1% AI. Coat the seeds thoroughly by mix-ing 1 g of seeds with 1 ml of the fungicide mixture.Seeds may be dried at 20°C and 40% relative hu-midity or sown immediately. The fungicide protectsyoung seedlings from damping off pathogens, suchas Rhizoctonia, Pythium, and Fusarium spp. Cap-tan can be substituted for Benomyl.

The primary seed-borne viral pathogens aretobamoviruses, including tobacco mosaic virus(TMV), tomato mosaic virus (ToMV), and peppermild mottle virus (PMMV). To minimize seed trans-mission, soak 2 g of seeds in 10 ml of 10% (w/v)trisodium phosphate (TSP) (Na3PO4

. 12 H2O) for30 min, transfer them to a fresh 10% TSP solutionfor 2 hours, then rinse in running water for 45 min.

January 2003AVRDC pub # 99-497RGuide

International Cooperators’

AVRDC - The World Vegetable Center

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This treatment can be done on freshly harvested ordry seeds. Or soak seeds for 4–6 hours in 5% (v/v)hydrochloric acid, then rinse in running water for 1hour. Dry them for storage, or sow immediately.

The primary seed-borne bacterial pathogen isXanthomonas campestris pv. vesicatoria (Xcv), thecausal agent of bacterial spot. To minimize Xcv in-fection, soak 2 g of seeds in 10 ml of 1.3% (v/v)acetic acid (shake occasionally) for 4 hours, rinsethe seeds with water three times, soak the seeds in1.25% (v/v) Clorox for 5 min, and rinse under run-ning water for 15 min. Or soak seeds in warm wa-ter (50°C) for 30 min, then dry them or sow imme-diately.

If you don’t know what pathogens, if any, are onyour seeds, then soaking in TSP followed by coat-ing with Benlate (see instructions for applicationabove) is a good general-purpose seed treatment.This should not affect germination in the near term(<1 year). Pathogen-free seeds sown in sterile soilrequire no treatment.

Seedling production

Times from sowing to plant emergence at differentsoil temperatures are shown in Table 1. Germina-tion varies depending on variety, seed quality, andsoil mixture. For optimum germination, sow seedsin a well-drained, sterile soilless mix at 25–28°C.Water daily.

One gram contains approximately 130 seeds.Approximately 300 g may be needed to plant 1 haat a density of 30,000 plants/ha, assuming 90% ger-mination and 90% survival after transplanting. Fillthe seedling tray with sowing medium, such as peatmoss, commercial potting soil, or a potting mix pre-pared from soil, compost, rice hulls, vermiculite, peatmoss, and/or sand. The potting mix should havegood water-holding capacity and good drainage. Werecommend a mixture of 66% peat moss and 34%coarse vermiculite. If you use non-sterile compo-nents, sterilize your potting mixture by autoclavingor baking at 150°C for 2 hours. If seedlings arestarted in a raised soil bed, the soil should be ster-ilized by burning a 3- to 5-cm thick layer of rice strawor other dry organic matter on the bed. This alsoadds minor amounts of P and K to the soil, whichhelps establish the seedlings.

Sow one seed per cell (or broadcast the seedslightly in a seedbed) and cover 1 cm deep. Coverthe seedlings with an insect-proof net, or sow them

inside a greenhouse or screenhouse. This providesshade and protects seedlings from heavy rain andpests, such as aphids, which transmit viruses. Wa-ter the seedlings thoroughly every morning or asneeded (not too wet, not too dry), using a fine sprin-kler. Irrigate with a 0.25% (w/v) solution of water-soluble or liquid fertilizer (10-10-10) when two trueleaves appear. If damping-off occurs, irrigate witha 0.25% (w/v) solution of Benlate or a similar fungi-cide.

If the seedlings have been grown in shade,harden them off by gradually exposing them to di-rect sunlight over 4–5 days prior to transplanting.On day one, expose them to 3–4 hours of directsunlight. Increase the duration until they receive fullsun on day four.

Transplanting

Recommended spacing varies depending on crop-ping system, soil type, and variety. AVRDC uses1.5-m wide beds (furrow to furrow), 30 cm high.We transplant two rows per bed. Rows are 55 cmapart, with 45 cm between plants within rows, for aplant population density of 29,630 plants/ha. Placethree or four granules of carbofuran (Furadan 5G)in each hole just prior to transplanting to guardagainst insect attack. Solarizing or flooding the soilprior to transplanting can reduce the number ofharmful organisms.

Under good conditions, seedlings are ready fortransplanting four weeks after sowing. The idealseedling has 4–5 true leaves, is disease-free,stocky, and has no flowers. Transplant in the lateafternoon or on a cloudy day to minimize transplantshock. Bury each plant to half its total height (rootto tip), and irrigate immediately after transplantingto establish good root-to-soil contact. Transplant-ing can be done manually or by machine.

Temperature (°C) Days after sowing

<15 No germination15 2520 13

25–35 8>35 No germination

Table 1. Influence of soil temperature on length oftime to plant emergence

Source: Knott's Handbook for Vegetable Growers,1997, p. 96.

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Fertilization

Nutrient requirements for a target yield of 28 t/ha(fresh weight) are listed in Table 2. Forty percent ofthe N should be applied as basal fertilizer beforetransplanting. The remaining 60% should besidedressed in three equal amounts at 2, 4, and 6weeks after transplanting (WAT). Fifty percent of theP and K should be applied as basal fertilizer, and theremaining 50% should be sidedressed at 4 WAT.

The amount of fertilizer to apply depends on soilfertility, fertilizer recovery rate, soil organic matter,soil mineralization of N, and soil leaching of N. Asoil test is recommended to determine the avail-able N, P, and K. The amount to be applied canthen be calculated based on your target yield andresidual nutrients. For example, if the target yield is14 t/ha and the soil test indicates that 50 kg each ofN, P, and K are available, you would need to applyabout 38 kg N and 30 kg K. Fifteen kilograms Nand 15 kg K would be applied as basal fertilizer,and the remaining N would be sidedressed at therate of about 7.5 kg/ha at 2, 4, and 6 WAT; the re-maining 15 kg/ha K would be sidedressed at 4 WAT.

Compost and/or green manure crops help in-crease soil organic matter content, which increasesthe soil’s buffering capacity. Applying fertilizerthrough a drip irrigation system is beneficial becauseit helps sweet peppers maintain constant growth.

Fertilizer recommendations depend heavily onlocal conditions, so consult your fertility manage-ment specialist for recommendations. Or conductyour own fertilizer trials to determine optimum rate.Refer to "Determining Fertilizer Rates for Crops inCropping Systems" in A Methodology for On-farmCropping Systems Research, published by the In-ternational Rice Research Institute (IRRI), LosBaños, Philippines (<www.irri.org>).

Field management

Mulching is recommended to reduce weed compe-tition, soil compaction, and soil erosion, and to main-tain a uniform root environment and conserve soilmoisture. Use rice straw (5 t/ha) or other organicmaterial, polyethylene plastic, or a combination ofmaterials. Plastic mulch must be laid down beforetransplanting; organic mulches can be laid downbefore or after transplanting. If plastic mulch is used,holes are cut in the plastic and plants are set di-rectly into the holes. During hot weather (>25°Cnighttime temperature), cover plastic mulch with

straw to reduce temperature in the root zone. Orirrigate and drain the field frequently to keep tem-peratures down.

Most sweet pepper varieties require staking toprevent lodging, particularly when they have a heavyload of fruits.

Sweet peppers are fairly shallow-rooted andhave low tolerance to drought or flooding. They willgenerally wilt and die if they stand in water for verylong, so drain fields quickly after heavy rain.

Crop water use will be relatively high whenevaporation is high and when the crop is floweringand setting fruit. If rainfall does not provide suffi-cient moisture, irrigate when the field reaches 40–50% available soil moisture. (To gauge soil mois-ture content, take a handful of soil from the bottomof a 15-cm-deep hole. Squeeze the soil. If it holdstogether when you release your grip, then there issufficient soil moisture. If the soil crumbles, thenit’s time to irrigate. Thorough irrigation providesuniform soil moisture, essential for optimum plantand fruit growth. Over-irrigation stimulates thegrowth of Phytophthora capsici. Furrow or drip irri-gation are recommended; sprinkler irrigation shouldbe avoided as wet leaves and fruits promote dis-ease development, especially at night. If overheadirrigation must be used, avoid evening irrigation.

If mulch is not available, or does not provide ad-equate weed control, several herbicides are avail-able, such as Lasso (alachlor 43EC), Amex (butralin47EC), Devrinol (napropamide 2E or 10G), and Dual(metolachlor 8E or 25G). Hand or hoe weeding canbe performed as needed. At AVRDC, we spray 0.4%(v/v) Lasso 43EC around the base of the plants 2–3 days after transplanting, and then we sprayRoundup (glyphosate) to control weeds in the fur-

Nutrient Nutrient Amountrequirement recovery needed*

(kg/ha) (%) (kg/ha)

N 70 40 175P 10 10 100

K 80 50 160

*Assuming no nutrients are available in the soil; the ac-tual amount of fertilizer applied should be adjusted down-ward based on the soil test results.

Table 2. N, P, and K requirements, expectedrecovery rate, and amount to apply for a targetyield of 28 t/ha (fresh weight) of sweet pepper

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rows later in the season. Care must be taken thatRoundup does not drift to the pepper plants. Thebest type of herbicide, rate, and method of applica-tion will vary depending on weed species, soil type,and temperature at time of application.

Integrated pest management (IPM) should befollowed. IPM has many components, includinggood hygiene, field scouting, mechanical control,cultural practices, biological control, and chemicalcontrol. See Table 3 for recommended options forcommon diseases and insects.

Use high quality, pathogen-free seeds and/orseedlings, and remove diseased leaves and plantspromptly. Practice good weed control and be care-ful not to damage the crop. If you have a diseaseoutbreak in one part of the field, work in other ar-eas of the field before working in the diseased area.To restrict the spread of tobamoviruses, dip yourhands and tools in milk before handling plants. Beaware that irrigation water can carry pathogens,such as Phytophthora. Mechanical control mea-sures include the use of nets, polyethylene mulch,and other barriers to keep insects away from plants.Yellow sticky traps can be used to catch insects.

Scout your fields at least twice a week, check-ing for pests and diseases. Count the incidence ofpests and diseases on 60 plants chosen randomlyin 0.1 ha. Decisions about spraying should be basedon the economic threshold (ET) of damage, but suchET values are generally not available for the majorpests and diseases that affect peppers. Consult yourlocal entomologist and/or pathologist for specificpest control recommendations for your area.

Planting resistant varieties is the best way tocontrol pests. Many varieties carry resistance to oneor more pests, but if no resistant variety is avail-able, try sowing the crop when pest pressure is low-est, and use the proper plant density. High plantdensities lead to thin, weak plants, which are moresusceptible to diseases and insects. Prevent plantsfrom being overloaded with fruits. Remove routinelyall fruits that set at the first bifurcation node, and allleaves and branches below the first bifurcation node.This will promote vigorous plant growth and reducethe spread of foliar diseases. Crop rotation, par-ticularly a rice–pepper rotation, reduces disease andinsect problems. Peppers should never follow otherSolanaceous crops, such as potato (Solanumtuberosum) or tomato (Lycopersicon esculentum),because these crops share many soil-borne dis-eases. Do not plant peppers after sweet potatoes(Ipomea batatas), due to allelopathic effects.

Biological control is the control of pests and dis-eases by their natural enemies. Four groups of bio-logical control organisms are commonly recognized:predators, parasites, microorganisms, and plantextracts and minerals. For more information on bio-logical control of pepper pests and diseases, con-tact Koppert Biological Systems at <www.koppert.nl/e005.shtml>. Plant extracts, such as neem seedextract and hot pepper extract, can be sprayed onyoung seedlings to help protect them from insects.

Chemical control of pests should be used mainlyas a corrective measure. If possible, choose a pes-ticide that targets the specific insect that is causingthe damage, and try to avoid pesticides that kill orinhibit the development or reproduction of benefi-cial organisms. Safeguard beneficial insects furtherby using selective application techniques, such asseed coating or application of systemic pesticidesin the seedling nursery. Dusting any pesticide gen-erally inhibits beneficial organisms, as does the ap-plication of a wetter or spreader to a pesticidesprayer. Choose pesticides that have short persis-tence, i.e., the effects of which last only a few days.Chemical pesticides should be applied in theevening, and workers should not be allowed intothe field until the recommended waiting period (usu-ally 12 or 24 hours) has passed. Wear protectiveclothing and follow all label directions when apply-ing pesticides. If multiple applications are neededto control a disease or insect problem, follow a pes-ticide rotation that includes at least three differentmodes-of-action.

Harvesting

Sweet peppers should be harvested when fruitsreach full size and become firm, but before turningcolor (unless they are intended for mature color:yellow, orange, or red). The fruits at the first andsecond nodes will be larger than subsequent fruits.It usually takes 35–40 days from flowering to opti-mum harvest stage, but the environment can affectthis. Stems of pepper plants are very fragile, so usea knife to harvest fruits. To avoid mechanical trans-mission of tobamoviruses, dip knives routinely in a3% (w/v) solution of TSP, or in milk.

For most sweet pepper varieties, production usu-ally lasts 6–8 weeks (3–4 harvests as fruits ripen).In temperate regions, sweet pepper production isusually halted by frost at the end of the season. Intropical and subtropical regions, pepper productiv-ity declines due to biotic and/or abiotic stresses.

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Table 3. Common diseases and insects of sweet peppers in Asia with their Latin names along withmode of transmission, symptoms, and some suggested IPM methods

Transfer mode

Phytophthora blight: Phytophthora capsici

Anthracnose: Colletotrichum spp. (acutatum, capsici, connoides, gloeosporioides)

Symptoms Suggested IPM methods

Bacterial spot: Xanthomonas campestris pv. vesicatoria

Bacterial wilt: Ralstonia solanacearum

Chilli veinal mosaic virus (ChiVMV), cucumber mosaic virus (CMV), potato virus Y (PVY)

Tobamoviruses

Aphids: Aphis gossypii, Myzus persicae

Thrips: Scirtothrips dorsalis, Thrips palmi

Mites: Polyphagotarsonemus latus

Soil-borne; rain splash. Nottransmitted by seed.

Damping off of young seedlings;root and crown rot; blight on leaves

Resistant varieties; raised beds;crop rotation; fungicides such asmetalaxyl and fixed copper

Rain splash in warm, wetweather. Transmitted in andon seeds.

Water-soaked spots (on fruits)expand to become dark anddepressed concentric rings

Pathogen-free seed; rotation;fungicides such as chlorothalonil ormancozeb; furrow irrigation

Rain splash; dewcondensation. Transmitted inand on seeds.

Irregular, light-brown, water-soakedlesions (on leaves) with thin whiteborders; defoliation

Resistant varieties; pathogen-freeseeds/seedlings; spray mixture ofmancozeb and fixed copper

Soil-borne. Not transmitted byseeds.

Leaves wilt, and drop off. (Whenput in water, cut stems ooze milkystreams of bacteria.)

Resistant varieties; good soildrainage and raised beds; rotationwith non-host crops such as rice

Aphids. Not transmitted byseeds.

Mosaic and mottled leaves; leafdeformation. Symptoms vary.

Resistant varieties; weed control;pesticides to control aphids; nets toprotect seedlings

Contact. Transmitted in andon seeds.

Leaf mosaic; stunted plants;systemic bleaching of leaves.

Resistant varieties; pathogen-freeseeds; dip tools and hands in milkor TSP prior to handling plants.

Flight; wind Leaf distortion and mottling;chlorotic leaf spots; black sootymold

Reflective mulches; rotation;predators and parasites; pesti-cidessuch as pirimicarb 50DP

Young leaves curl upwards; fruitsnetted with cork-like streaks

Weed control; crop rotation;predators and parasites; rotateinsecticides

Leaves curl downwards; growingpoint and young leaves are bronzedand stunted; cork-like fruits

Tolerant varieties; weed control;crop rotation; miticides such asabamectin and dicofol

Flight; wind

Flight; wind

For more information see "Pepper Diseases: A Field Guide" by LL Black, SK Green, L Hartman, and JM Poulos,published by AVRDC in 1991