VIRAL DISEASES –

UNRELENTING MALADIES IN CARDAMOM PLANTATIONS

Biju C.N and Praveena R

Indian Institute of Spices Research,
Cardamom Research Centre,
Appangala, Heravanadu Post,
Madikeri 571 201, Karnataka.

A. I. Bhat

Division of Crop Protection,
Indian Institute of Spices Research,
Marikunnu, Calicut673 012, Kerala

Small cardamom (Elettaria cardamomum Maton) is a perennial, herbaceous monocot, which belongs to the rhizomatous family, Zingiberaceae. In India, cultivation of cardamom spreads in an area of 71,170 hectares with a production of 11, 000 tonnes. Among the cardamom cultivating states, Kerala has the maximum production of 8,545 tonnes, while the contribution of Karnataka and Tamil Nadu are 1,725 and 965 tonnes, respectively. Though India is blessed with favourable agro-climatic conditions for cultivation of cardamom, it is paradoxical that the productivity is no way near to the world average. Rampant incidence of diseases, especially the viral diseases has immensely contributed to a rapid decrease of production over years and still remains as one of the bottleneck encountered by the cardamom industry in achieving sustainable production levels. Among the viral diseases, mosaic/katte/marble disease incited by Cardamom mosaic virus (CdMV) is considered as a major production constraint. Besides this dreadful disease, chlorotic streak caused by a strain of Banana bract mosaic virus (BBrMV) is an emerging disease of recent origin. Other viral diseases such as kokke kandu, Nilgiri necrosis and infectious chlorosis are confined only to certain endemic areas of cardamom growing tracts.

 

MOSAIC DISEASE

 Mosaic disease, also known as katte/ marble is the most widespread and destructive among the viral diseases of cardamom. The disease is prevalent throughout all the cardamom growing regions of South India, with an incidence ranging from 0.01 to 99 per cent. Crop losses due to the disease depend on the growth stage of cardamom plants at the time of infection. Infection in the early stages of development results in total loss of the crop while, late infection results in a gradual decline in productivity. Due to katte infection, under monocropping and mixed cropping conditions in areca gardens, yield reduction to the extent of 38, 62 and 68.7 per cent is observed during first, second and third year of infection, respectively. In general, total decline in both production and productivity of the affected plantations occurs within a period of thre to five years after initial establishment of the disease.  

The disease initially manifests on youngest leaf of the affected plants as slender chlorotic flecks. These flecks eventually develop into pale green discontinuous stripes, which run parallel to the veins from midrib to the leaf margins. Later, mottling develops on the leaf sheath as well as on the pseudostems. Young plants when infected rarely become productive.  

Cardamom mosaic virus(CdMV), the causal agent of kattedisease belongs to the genus Macluravirus of the family Potyviridae. The virus is not transmitted through seed, soil, root to root contact and through cultural operations. Dissemination of the virus is mainly mediated by the aphid vector and also through the use of infected planting materials. About 13 species of aphids are reported to transmit the virus of which, Pentalonia caladii which breeds on cardamom, Colocasia and Caladium is the principal vector.  

In plantations, primary spread of the disease occurs randomly due to the activity of viruliferous winged forms of the vector. Generally, early expression of the symptoms occurs during the active growth phase of the plant i.e., May to November while, during the months of December to March, expression of the symptoms is delayed. Apart from cardamom, several plants belonging to the Zingiberaceae family viz., Amomum canneacarpum,A. involuctrum, A. subulatum, Alpinia neutans, A. mutica, Curcuma neilgherresnis, Zingiber cernauum are also found to be susceptible hosts to the virus.  

CHLOROTIC STREAK DISEASE 

Chlorotic streak is a newly reported viral disease of cardamom. The disease is reported from the cardamom growing zones of Karnataka and Kerala. In Kerala, the disease incidence ranged from 0 – 15 per cent, with the highest incidence in Vythiri Taluk of Wayanad district and in Karnataka, incidence ranged from 0-5 per cent with the highest incidence (five per cent) in Uttara Kannada districts. 

The disease is characterized with continuous or discontinuous spindle shaped yellow or light green streaks intravenously and along the midrib, which later coalesce together and impart yellow or light green colour to the veins. Formation of discontinuous spindle shaped mottling along the pseudostem and petiolesare also observed. In the advanced stages of disease progression, size of the leaves gets reduced and production of new tillers is suppressed. 

The incitant of chlorotic streak disease is a strain of Banana bract mosaic virus (BBrMV).Transmission of BBrMV infecting cardamom is not yet established using aphids, sap or seed.The disease mainly spreads through infected planting materials.

CARDAMOM VEIN CLEARING ORKOKKE KANDU DISEASE 

Cardamom vein clearing disease is restricted only to a few endemic pockets in Karnataka. The disease is reported from Kodagu, Hassan, Chickmagalur, Shimoga and North Canara districts of Karnataka. The affected plants decline rapidly with a yield reduction upto 62-84 per cent in the first year of the crop. The affected plants become stunted and perish within one to two years after taking infection.  

The disease manifests on the leaves as continuous or discontinuous clearing of the veins. Subsequently, rosetting, loosening of leaf sheath and shredding of leaves are also noticed. Newly emerging leaves get enmeshed in the older leaves. Subsequently, the tiller assumes a ‘hook-like’ appearance and hence the name kokke kandu. Mottling symptoms develops on the leaf sheaths and the immature capsules exhibit shallow grooves on the outer rind. Cracking of fruits and partial sterility of seeds are also associated with the disease.  

The exact etiology of the disease is not yet established. However, infected cardamom samples showed positive serological relationship with potyviruses, indicating the possible involvement of a virus belonging to the genus, Potyvirus. The virus is not transmitted through seed, soil, root, sap, mechanical contact and farm implements. The disease is transmitted mainly through cardamom aphid, P. caladii. Primary sources of inoculum includes, infected planting materials obtained from disease affected plantations. Primary spread to a new plantation mainly occurs due to the activity of incoming alate viruliferous vectors.  

CARDAMOM NECROSIS DISEASE (NILGIRI NECROSIS DISEASE)

Cardamom necrosis disease was first noticed in severe form in Nilgiris district of Tamil Nadu and hence commonly known as Nilgiri necrosis disease. The symptoms are manifested on the young leaves as whitish to yellowish continuous or broken streaks proceeding from the midrib to the leaf margins. In the advanced stages of infection, these streaks turn reddish brown leading to shredding of the leaves. The leaves are reduced in size with distorted margins. Early infected plants produce few panicles and capsules and in the advanced stages of infection, tillers are highly stunted and fail to bear panicles and capsules. 

The virus causing Nilgiri necrosis disease belongs to Carlavirus group. Seed, soil, sap, insects and mechanical means do not transmit the disease. The disease spreads mainly through infected planting material. The pattern of spread of this disease is also similar to katte disease; however, rate of spread is comparatively low in the plantations.  

INFECTIOUS VARIEGATION DISEASE 

This disease was first noticed in Vandiperiyar region of Kerala with an incidence of 15 per cent. Later it was also reported from Kodagu, Hassan and North Canaradistricts of Karnataka. Infected plants exhibit typical variegated symptoms on the leaves with characteristic slender to broader radiating stripes of light and dark green on the lamina. Distortion of leaves, tillers and stunting are other associated symptoms. The infected plants become unproductive within the same year of infection.

MANAGEMENT OF VIRAL DISEASES 

Cardamom is propagated mainly by vegetative means and the viruses infecting cardamom primarily spreads through the planting material. Systemic nature of viral diseases further aggravates the problem, as it would be difficult to obtain healthy, virus-free planting materials from infected mother stock. Prevention is better than cure is the thumb rule to manage viral diseases, effectively and economically. In view of this, combinations of strategies need to be formulated and adopted for management of viral diseases.  

PRODUCTION AND USE OF VIRUS – FREE PLANTING MATERIAL 

Primary, secondary/ polybag nurseries as well as clonal nurseries should be raised in isolated locations, away from the main plantations.

 
The clones obtained from affected plantations should be strictly avoided for establishing new plantations and for undertaking replanting in the existing plantations. 

If tissue culture raised plants are used, it is obligatory to check presence of virus in the mother plant. If the mother plant is infected, the plantlets derived from this also will harbour and facilitates subsequent spread of the virus.  

Volunteer plants that grow from the remnants of infected plants are potential primary sources of inoculum and makes further spread of disease within the plantations easier. Removal and destruction of the infected volunteers and its total avoidance in the vicinity of nursery sites are highly essential for checking the spread of viral diseases.  

Regular monitoring, tracing, removal and subsequent destruction of infected plants and collateral hosts are indispensable for managing viral diseases. The removed plants should be either burnt or buried deep in the soil. 

As visual inspections for symptoms may not be always sufficient to confirm the virus-free status of the planting material, use of sensitive diagnostic tools based on serology [enzyme linked immunosorbent assay (ELISA) or electro-blot immunoassay] or nucleic acid [polymerase chain reaction (PCR)] is essentially recommended. Indian Institute of Spices Research (IISR), Kozhikode has developed PCR based diagnostic kits for the detection of both CdMV and BBrMV in the cardamom plants.  

VECTOR MANAGEMENT  

The insect vectors whenever noticed on the plants should be controlled by adopting insecticidal sprays. Insecticides like dimethoate or monocrotophos @0.05 per cent can be used to control aphids and other sucking insects.  

Spraying neem based products at 0.1 per cent concentration were also found to reduce population build up of the aphids on cardamom.  

Spraying recommended insecticides after undertaking trashing operation further enhances efficacy of the application.

Periodical removal of senile old parts, which are the breeding sites for aphids and other collateral hosts like Colocasia and Caladium, effectively reduces the aphid population and check subsequent spread of viral diseases.  

RESISTANT SOURCES  

IISR Vijetha, the mosaic disease resistant variety is recommended for cultivation in katte prone areas

 

 

STRATEGIES TO CURTAIL FUNGAL DISEASES

 IN CARDAMOM PLANTATIONS

 

Praveena, R., Biju, C.N. and Ankegowda, S.J.

Indian Institute of Spices Research,

Cardamom Research Centre, Appangala,

Heravanadu Post, Madikeri 571 201

Karnataka

 

The serenity of unblemished cardamom plants vividly coloured in green shade bathed in golden rays filtering through the canopy of shade trees is certainly a feast for eyes. However, for centuries, the enchanting queen of spices clan is waging unrelenting battles against a battalion of pathogenic microbes, having the potential to steal away the picturesque of cardamom tracts. The microclimatic conditions prevailing in the cardamom ecosystem often favours these unsolicited intruders to proliferate and inflict damage to the plants. Cardamom suffers from the attack of various pathogenic microbial agents, of which diseases caused by fungi are of major concern. The disease induced by these organisms often attains severe proportions in nurseries and in plantations, where adequate crop protection measures are seldom adopted.

In primary nurseries, leaf spot caused by the fungus Phyllosticta elettariae is a destructive disease and appears mostly during February- April months with the receipt of summer showers. The disease manifests as small circular or oval spots, which are dull white in colour. These spots later become necrotic and leave a hole (shot hole) in the center of the affected portion (Fig.1).

In secondary nurseries, another type of leaf spot caused by Cercospora zingiberi is of common occurrence. The symptoms appear as yellowish to reddish brown coloured rectangular patches on the lamina, almost parallel to the side veins. In the later stages lesions colour of the lesions turns to muddy red.

 

Damping off or seedling rot usually appears in the primary nurseries during the monsoon season, when there is excessive soil moisture due to inadequate drainage. The disease is caused by soil borne fungi, Pythium vexans and Rhizoctonia solani and the incidence varies from 10 to 60 per cent. In severe cases, the seedlings wither and collapse in masses.

DISEASE MANAGEMENT IN NURSERY

·         Practice of raising nurseries regularly in the same site should be avoided.

·         Cardamom seeds should be sown in the month of August – September, to ensure sufficient growth of seedlings, so that seedlings develop sufficient tolerance to the disease.

·         In primary nurseries, thin sowing may be practiced to avoid overcrowding of seedlings.

·         Wherever required, provide adequate drainage facilities in primary and secondary nurseries.

·         Cardamom seedlings affected with damping off should be removed and proper phytosanitary measures should be practiced in the nurseries.

·         When leaf spot incidence is observed, spray carbendazim (Bavistin) @ 0.2 per cent on the leaves at fortnightly intervals. Two to three rounds of spraying may be undertaken depending on the intensity of the disease.

·          On initiation of damping off, drench the nursery beds with copper oxychloride (COC) (0.2 per cent) @ three to five liters per square meter. Two to three rounds of COC drenching may be resorted at 15 days interval, depending on the severity of the disease.

In cardamom plantations, capsule rot/Azhukal and clump rot were reported to be the most important fungal diseases. However, in the recent past incidence of several minor diseases are increasing resulting in a setback in the production and productivity of cardamom.

 

AZHUKAL OR CAPSULE ROT

 ‘Azhukal’ is a serious problem in cardamom plantations and is  a major constraint in the successful cultivation of cardamom in Kerala and elsewhere. The disease is caused by Phytophthora nicotianae var. nicotianae and P. meadii. During heavy and incessant rainfall conditions, crop loss as high as 40 per cent occurs.

 

The disease appears in the form of water soaked lesions on tender leaves and capsules. On the leaves, water soaked lesions later turns necrotic, surrounded by yellow halo. In advanced stages, the leaves rot and shred along the veins. Finally, the affected leaves break at the base of petiole and remain hanging. Plants of all ages are susceptible to the disease. However, under field conditions disease incidence is noticed mainly on the bearing plants. Infection on immature capsules results in rotting which emit a foul smell and later, fall off (Fig.2). Mature capsules when infected, become shriveled up on drying.

The disease attains maximum severity during the months of heavy and continuous rainfall which facilitates build up of high relative humidity, especially during July. Heavy shade and closer spacing coupled with favourable weather conditions predispose the plants to infection.

MANAGEMENT

·         Trashing and destruction of the infected parts should be done as a phytosanitary measure prior to the onset of southwest monsoon (May).

·         The dried leaves and leaf sheaths from the basal region of the plant should be removed to the maximum extent possible.

·         Thick shade may be regulated by gentle lopping of branches of the shade trees.

·          In plantations, wherever water stagnation is a problem, adequate drainage should be ensured. 

·         Prophylactic sprays with Bordeaux mixture (one  per cent) should be given during May-June and subsequent sprays may be undertaken during July –August. If the monsoon prolongs, a third spray may be given during September.

·         When the disease makes it appearance Fosetyl-Al (Aliette ) 0.2 per cent or potassium phosphonate (Akomin) 0.5 per cent can be sprayed @ 500-750 ml per plant.

·         Drenching of plant basins with 0.2 per cent copper oxychloride (COC) reduces soil inoculums levels and prevents further spread of the disease.

·         Application of potential antagonistic fungal agents like Trichoderma viride or T. harzianum mass multiplied on suitable carrier media to the plant basins @ 1kg during May and September –October further helps in checking soil borne diseases. If the soil is drenched with COC or other fungicides, Trichoderma should be applied only after 15 days.

 RHIZOME ROT

 

Rhizome rot also known as clump rot is one of the earliest reported fungal diseases in cardamom.  Soil borne pathogenic fungi such as, Pythium vexans,  Rhizoctonia solani and Fusarium sp. are the causal organisms .The disease initially manifests as yellowing of foliage, followed by drooping of leaves. The collar region becomes brittle and breaks off at slight disturbance. As the disease advances, rotting extends to the rhizomes as well as roots and the affected tillers subsequently fall off (Fig.3) . Rotten rhizomes become soft, dark brown coloured and emit a foul smell. Lodging of tillers due to rhizome rot diseases is severe during the monsoon season.

 

MANAGEMENT

 

·         Phytosanitary measures as recommended in the Azhukal disease may be practiced.

·         Once the disease appears in the plantations, basins of the cardamom plants should be drenched with two to three liters of COC (0.2 per cent). Drenching of COC may be repeated at 30 days interval for two to three times depending on severity of the disease.

·         Application of Trichoderma culture multiplied on a suitable substrate helps in promoting growth of the plants as well as checking the disease development.

 

LEAF BLIGHT

In recent years, leaf blight popularly known as Chenthal caused by Colletotrichum gloeosporioides gained considerable importance. The disease which appears during mid- monsoon, becomes severe during late monsoon periods (October-November) and declines by March. The symptoms initially manifests on the leaves as yellow lesions which later elongate to form necrotic streaks that run parallel to the veins. Several such lesions later coalesce to form yellowish-brown to reddish-brown patches, which subsequently withers off (Fig. 4). In the advanced stages of disease development, several such lesions develops on both young as well as older leaves which eventually dries up and gives a burnt appearance to the affected plants. Intermittent rains and prevalence of misty conditions in the plantations favours the incidence and spread of the disease.

 

MANAGEMENT

 

            Timely and meticulous adoption of recommended cultural practices and plant protection measures reduces the incidence of leaf blight to a considerable extent.

·         Leaf blight affected portions should be destroyed during May, before the onset of monsoon.

·         The disease is more severe under exposed conditions, due to poor adoption of shade regulation practices. Intensity of the disease can be reduced significantly by providing adequate shade in the plantations. It is appropriate to regulate shade before the onset of South –West monsoon season. Optimum shade levels may be maintained in the plantations by allowing upto 40-60 per cent filtered light.

·          As a prophylactic measure, Bordeaux mixture (one per cent) @ 500 ml to one liter /plant should be sprayed during May – June before the onset of monsoon, which may be repeated during the months of August- September.

·         Once leaf blight appears in the field, fungicide sprays with the combination product of carbendazim and mancozeb (Companion) 0.1 per cent or carbendazim (Bavistin) 0.2 per cent @ 500 - 750 ml/plant may be adopted. Spraying should be undertaken during August-September which may be repeated for two to three times at an interval of 30 days depending on the severity and extent of damage. Adequate care should be taken that the entire foliar portion is covered with the spray solution.

 

LEAF BLOTCH

 

Leaf blotch, comparatively less important disease is caused by Phaeodactylium alpiniae. During monsoon season, lesions develop at the tip or near the leaf midribs which subsequently turns to brownish necrotic patches. The mycelia and conidial masses of the fungus are visible as thick grey coloured mats or powdery coatings on the underside of the blotched area. During dry weather conditions infection is restricted to smaller lesions and spread of the disease in plantations is also limited. The disease can be managed by adopting foliar sprays with Bordeaux mixture (one per cent), copper oxychloride (0.2 per cent) or mancozeb (0.3 per cent).

 

STEM LODGING

 

 The disease mainly affects the tillers and widely distributed in the cardamom plantations in Idukki district of Kerala and lower Pulney Hills of Tamil Nadu. The disease is incited by Fusarium oxysporum and the disease appears commonly during the post-monsoon periods

 The disease is characterized by the formation of pale discoloured patches on the middle portion of the tillers, which lead to dry rot. As a result of the infection, the tillers become weak and break off at the point of infection. The partially broken tillers bend downwards and hang from the point of breakage (Fig. 5). When the infection occurs at the collar region, the tillers fall of giving a lodged appearance. In the affected tiller leaves and leaf sheaths dries off. Spraying with Bavistin (0.2 per cent) or Hexaconazole (Contaf) 0.2 per centcan manage the disease.

 

ROOT TIP ROT

The disease makes its appearance during post monsoon season and attains severity during summer. The symptom includes rotting of the root tips followed by die back of roots (Fig. 6). The lower leaf of affected tillers become yellowish and gradually dries off. The disease is caused by Fusarium oxysporum . Spraying and drenching plant basins with carbendazim (Bavistin) 0.2 per cent or hexaconazole (Contaf) 0.2 per cent are recommended and the application may be repeated at 15- 20 days interval for effective management of the disease.

PROPAGATION TECHNIQUES IN SMALL CARDAMOM

 

S.J.Ankegowda and Biju C.N.
Indian Institute of Spices Research,
Cardamom Research Centre,
Appangala,
 Heravanadu Post,
Madikeri 571 201, Karnataka.

 

Small cardamom (Elettaria cardamomum Maton), the exquisite member of spice family, Zingiberaceae originated in the evergreen expanse of Western Ghats. The spice endowed with its alluring qualities is appropriately acknowledged as “Queen of Spices”. Several varieties with superior quality traits for high yield, resistant to pests and diseases have been evolved through selection and hybridization process and being widely accepted among the farming community across the cardamom growing regions. Effective transfer of these desirable traits to the next generation without any dilution of the genetic fidelity and also to produce ample quantity of quality planting materials to cater needs of the farmers, appropriate methods of propagation need to be adopted. Cardamom is generally propagated by seeds and suckers (vegetative/clonal propagation). However, being a cross pollinated crop, considerable variation is observed in the seedling progenies and the seedlings may not possess all the qualities of the mother plant. Hence, vegetative propagation is normally adopted for mass multiplication of elite clones and also to maintain the genetic purity.

Seed propagation

Different steps involved in raising nurseries using seed material are given below:

Primary nursery

Selection of nursery site:

 

Gentle sloppy area, preferably adjacent to a perennial water source is suitable for raising the nurseries. Initially, the selected area is prepared by removing all existing vegetation, stumps, roots, stones etc. In the cleared area, beds are prepared with one meter width, 20 cm height and desirable length, generally six meters. Jungle top soil is spread to a thickness of two to three cm on the beds.

Selection of seeds:

Seeds should be collected from vigorously growing high yielding plants with well formed compact panicles and well ripened capsules. The plants should be free from the infestation of pests and diseases. Number of flowering branches produced on the panicles, percentage of fruit set and number of seeds per capsule are given due consideration while selecting the mother plants for collection of seed material. Apart from these desirable attributes, the mother clump should also have more number of tillers (shoots) per plant. On an average, one kg fruits contain 900-1000 capsules and 10-15 seeds per capsule. On an average, one kg of seed capsules is required to produce 3000-5000 seedlings and half kg seed capsules are sufficient to produce seedlings for an area of one acre. Seeds are collected from fully ripened capsules, preferably from second or third round of harvest during September. The seeds are either washed in water and sown immediately or mixed with wood ash and dried for two to nine days before sowing. Immediate sowing of seeds produces good results and is also the widely accepted method. After harvesting, the extracted seeds are immersed in water to separate immature and degenerated seeds. The seeds are then thoroughly washed with water to remove mucilaginous coating covering the seeds. After draining out water, the seeds are mixed with wood ash and dried under shade.

The seeds which are sown immediately after harvest germinate early and uniformly. The seedlings will be ready for transplanting 10 months after sowing. The ideal sowing season is reported to be November - January for Kerala and Tamil Nadu and September for Karnataka.

Pre-sowing treatments of seeds:

Cardamom seeds posses a hard seed coat, which delays its germination. Studies have been undertaken to evaluate the effect of pre-sowing treatments to enhance germination percentage (Table 1).

Table 1.	Effect of acid treatment on seed germination of cardamom
Treatment	Mode	Duration	Germination percentage (increase or decrease over control)
Con. Nitric acid	Soaking	five minutes	nine per cent increase
Conc. Hydrochloric acid	Soaking	five minutes	Increased germination
25 per cent Nitric acid	Soaking	10 minutes	55 per cent increase (fresh seeds) 25 per cent increase (six to eight months old seeds)
25 per cent Acetic acid 25 per cent Hydrochloric acid 25 per cent Nitric acid	Soaking	10 minutes	90 per cent germination
Acetone	Soaking	10 minutes	Increased germination

 

Soaking cardamom seeds in dilute or concentrated acids for 5-10 minutes increases the germination percentage to a considerable extent. In addition, soaking seeds in solutions of gibberelic acid (GA₃) and ethrel enhances germination significantly.

Apart from other factors, ambient temperature plays a vital role in germination process. Prevalence of low temperature in the cardamom growing areas reduces germination as well as delays the process of germination. In general, cardamom seeds fail to germinate at temperatures lower than 15^oC and greater than 35^oC. The ambient temperature prevailing during the months of September to October favours germination of the seeds.

Sowing

Fig. 1 - Primary nursery in raised beds under protective overhead shade net

On the beds, the seeds are sown in lines usually not more than one cm deep. Rows are spread at 10 cm apart and seeds are sown one to two cm apart within a row. Deep sowing should be avoided for better and quicker germination. Seed rate of 30 to 50 grams may be adopted for 6x1 meters size bed. After sowing, the beds are covered with a thin layer of sand and then with mulch materials such as dried leaves/grass or paddy straw. Supporting twigs are laid across the bed to avoid contact of mulch materials with the soil. The beds are irrigated at regular intervals to maintain adequate moisture. Germination commences in about 20-25 days after sowing, which may continue for a month or two. The mulch materials are removed soon after the commencement of germination. The young seedlings are protected from exposure to direct sunlight and rain by providing overhead pandals (Fig. 1).

Mulching of beds

Mulching seedbeds with appropriate materials influence germination of the seeds. Paddy straw and dry leaves are considered as ideal mulch materials. Besides these materials, mulching with coconut coir dust, paddy straw or goose berry leaves is also reported to enhance the germination.

 Secondary nursery

Generally two methods viz., bed and poly bag are adopted to raise seedlings in secondary nurseries.

 Bed nursery:

The beds are prepared as described in primary nursery. A layer of cattle manure is spread over the bed and thoroughly mixed with soil. Seedlings of four to five leaf stages from the primary nursery beds are transplanted in the secondary nursery at a distance of 20 to 25cm. In Karnataka, where seeds are sown during August-September, transplanting is normally undertaken during November-January. While, in Kerala and Tamil Nadu, seedlings from primary beds are transplanted to secondary nursery beds at a spacing of 20 x 20 cm during June-July. It is observed that, rate of seedling mortality is higher when transplanted at second leaf stage. Nevertheless, the mortality can be minimized to a greater extent by transplanting at four-five leaf stage.

On an average, 120 gram nitrogen, 20 gram phosphorus and 300 gram potash, 50 gram magnesium and 75gram calcium are removed from a bed planted with seedlings. To promote uniform growth, 250 gram mixture made of nine parts of NPK 17:17:17 and eight parts of zinc sulphate dissolved in 10 liters of water may be sprayed once in 15-20 days, starting one month after transplanting. It is observed that application of 45 gram N, 30 gram P₂O₅ and 60 gram K₂O per bed of 2.5 x 1 meters size in three equal splits at an interval of 45 days results in better growth and higher number of tillers. First dose of fertilizer may be applied 30 days after transplanting in the secondary nursery. Earthing up operation should be carried out after each fertilizer application and hand weeding should be undertaken once in every 20-25 days.

It is recommended to shift the nursery site once in two to three years to prevent buildup of pests and diseases and also to reduce the damage caused by these agents.  However, in those areas where such practice is not possible due to non-availability of alternate sites, the proposed nursery area may be left fallow for a year after deep digging/ploughing. This practice would help in exposing soil-borne pests and survival structures of pathogens to sun, thus killing them and brings down the inoculum levels to a considerable extent. By meticulously adopting the recommended packages, the seedlings would be ready for transplanting in main field, 10 months after sowing.

 Poly bag nursery

 

Fig. 2 - Secondary nursery raised polybag under rainout shelter

Polythene bags of 20x20 cm size and 100 gauge thickness with three to four holes at the bottom are used to raise seedling in poly bag nurseries. The bags are filled with jungle top soil, cowdung and sand in the ratio 3:1:1. The bags are arranged in rows of convenient length and breadth for easy management. Seedlings at four to five leaf stages are transplanted into each bag (one seedling per bag) (Fig. 2). Providing adequate space between the bags facilitates better production of tillers. The advantages of raising seedlings in poly bags are:

·         Seedlings of uniform growth and tillers are produced.

·         Duration of the nursery can be reduced to five to six months as against 10 to 12 months in the secondary nursery. in

·         Better establishment and growth of seedlings in the main field.

Cardamom plants from secondary nursery or poly bags can be transplanted to the main field during last week of May after the receipt of pre-monsoon showers or during the first week of June after commencement of the south west monsoon.

Vegetative propagation

Suckers from elite clones with desirable features like high production potential and resistant to pests as well as diseases are used for establishing plantations. Plants raised from suckers starts bearing earlier than plants produced from seeds. The planting material should not be collected from areas endemic to diseases, especially the viral diseases.  

Rapid clonal propagation

High yielding varieties/selections are generally multiplied in isolated clonal nurseries       (Fig. 3). Disease free high yielding plants are selected and sub cloned for subsequent multiplication. High yielding plants free from pest and diseases, with desirable characters like bold capsules with green colour are to be selected from plantations and part of the clump has to be uprooted for clonal multiplication leaving the mother clump in its original place to induce subsequent sucker production for further use.

 

Fig. 3 - Clonal nursery

 

For rapid multiplication the following agro-techniques need to be followed:

·         The planting unit should consist of one grown up sucker (rhizome) and a young growing shoot.

·         Trenches with 45 cm width and depth and convenient length have to be opened and filled with jungle soil, compost and topsoil.

·         The rhizomes (planting unit) are planted at a spacing of 1.8 x 0.6 meters in trenches, thus accommodating 9259 plants per hectare of clonal nursery area.

·         Overhead protection by erecting pandals, regular irrigation (once in a week during November to May) and application of fertilizers @ 48:48:96 grams. NPK per plant in two splits need to be practiced.       

·         On an average 32 - 42 suckers will be produced after 12 months of planting one planting unit. Taking the barely minimum of 50 per cent of this suckers/clump, 16-21 planting units (one grown up sucker along with a growing young shoot i.e. sucker) from one mother-planting unit after 12 months are produced.

·         Drenching the trenches with cowdung slurry with two kg of nutrients mixture (19:19:19 NPK) mixed in 200 liters of water, further hastens production of suckers and enhances the growth.

·         In an area of one hectare clonal nursery, 1,48,144 to 1,94,439 planting units can be produced after 12 months of establishment.

Major pests and diseases in nursery and management

Major diseases observed in the nursery are leaf spots, damping off/seedling rots and leaf rots.

 

Primary nursery leaf spots

 Primary nursery leaf spot caused by, Phyllosticta elettariae is a destructive disease in nurseries. The disease makes its appearance during the months of February- April with the receipt of pre-monsoon showers. The disease initially manifests as small dull white round to oval spots, which later turn necrotic and leave a hole (shot hole) in the center of necrotic area. The spots may be surrounded by water soaked area. The disease is more severe in open nurseries exposed to direct sunlight. However, the seedlings develop tolerance as they attain maturity.

The disease can be contained by undertaking the following management measures:

·         Sowing of the seeds may be undertaken during August – September, to ensure sufficient growth of seedlings, so that they develop tolerance to the disease.

·         Provide adequate shade by providing overhead pandals with coir material/ mat/agro- shade nets/thatched coconut fronds.

·         Prophylactic spraying with fungicides such as mancozeb (0.2 per cent) may be given on the leaves. First spray is to be given during March-April, depending on the receipt of summer showers and subsequent sprays at fortnightly intervals. Two to three rounds of spraying may be given.

·         Clipping and destructing   severely affected leaves after spraying is to be done to arrest further spread to the remaining healthy leaves.

·         Avoid raising nursery continuously in the same site.

Secondary nursery leaf spot

In secondary nurseries, another type of leaf spot incited by Cercospora zingiberi is of common occurrence. The disease is characterized with the formation of yellowish to reddish brown coloured rectangular patches on the lamina, which run parallel to the veins. In the advanced stages, the lesions assumes muddy red colour.

Prophylactic spraying with mancozeb (0.2 per cent) on the foliage effectively prevents the establishment and subsequent spread of the disease.

Nursery leaf rot

Normally seedlings of three to four months old are more vulnerable to the disease. The disease, which is of limited occurrence in the nurseries, is caused by Fusarium sp. and Alternaria sp. The symptoms include, formation of water soaked lesions on the leaves, which later becomes necrotic patches leading to decay of affected areas. Usually the damage is more pronounced on the leaf tips and distal portions of the foliage. Under favourable conditions, rotting extends to petiole and leaf sheaths also.

Avoiding excessive watering in the nurseries prevents initiation and further proliferation of the disease. When the disease is noticed in the nurseries, spray the seedlings with carbendazim (0.2 per cent) twice at 15 days interval after destroying the affected plant parts.

Damping off or seedling rot

 The disease appears usually in the nurseries during rainy season and favoured by the availability of excess soil moisture due to inadequate drainage facilities. The disease is caused by soil-borne fungi such as Pythium vexans and Rhizoctonia solani. Fusarium oxysporum also causes similar seedling rot, resulting in the wilting and withering of entire seedlings. In the initial stages of disease development, the leaves turn pale and with yellowish tips. Gradually, the symptoms spread over the entire leaf lamina, extending to leaf sheath and results in wilting of seedlings. The collar portion decays and the entire seedlings collapse.  In mature seedlings, rotting extends from the collar region to the rhizomes, resulting in decay and ultimate death of the plant.  

·                     In primary nurseries, practice thin sowing to avoid overcrowding of the seedlings.

·                     Prevent water stagnation by providing adequate drainage facilities.

·                     Remove affected seedlings and maintain proper phyotsanitary measures in the nursery.

·                     When infection is noticed, drench the nursery beds with copper oxychloride (0.2 per      cent).

·                     Pre-sowing treatment of seeds with antagonistic biocontrol agents such as Trichoderma or Pseudomonas protect the seedlings in the early stages of growth. Application of Trichoderma at 100 grams per square meter of the bed also helps in reducing the disease spread.

Damping off

The disease is a major problem in the secondary nurseries. Seedlings which have attained maturity (six to eight months old) are more susceptible to the disease. The disease is caused by soil-borne fungi, Pythium vexans and Rhizoctonia solani. Another soil-dwelling pathogen, Fusarium sp. incites root rot in the secondary nurseries. The disease attains severity during the monsoon season, when the soil moisture level is excess due to inadequate drainage. The diseases initiates on the leaves as pale yellow discolouration and withering of seedlings. Rotting or decay starts at the collar region and it also spreads to the rhizome as well as roots. In severe cases, the collar region breaks off and the seedlings collapse.  

·                     Uproot and destroy all the affected seedlings in the nursery.

·                     Avoid use of excess water for irrigation.

·                     Remove mulch materials a soon as the disease is noticed from the nursery beds and rack the soil gently.

·                     Drench the nursery beds with copper oxychloride (0.2 per cent) at the rate three to five liters per square meter. Two to three rounds of drenching should be resorted at 15 days interval. 

Pest Management in nurseries

 In nursery stage seedlings are affected by cut worm, shoot borer, root grub, leaf thrips and root knot nematode. Root grubs and root not nematode pose more problem in two season nurseries. To manage whole pest complex the following measures are to be followed at various stages of nursery.

Cultural Practices

·         Raise nurseries away from main plantations to reduce possibilities of infestation and reinfestation from the nearby infested plantations.

·         Provide sufficient organic fertilizers to encourage better vegetative growth.

·         Shift nurseries repeatedly to overcome soil- borne pest problems like root knot nematodes and root grubs.

·         Catch and destroy the beetles of root grubs using insect nets especially in 2 season nurseries.

·         Collect the cut worms hiding in the mulch in the affected area and destroy.

Chemical control

 

Insecticides like quinalphos (0.05 per cent), fenthion (0.075 per cent) or dimethoate (0.05 per cent) may be used to tackle the pest problem. The sprays may be undertaken at monthly intervals starting from rapid tillering stage. In the old nursery sites, exposed sandy loam areas and two season nurseries root knot nematode assumes severe proportion. Apply one round of carbofuran or phorate at 30-40 g/m² in one season nursery at rapidly tillering stage and apply two rounds of granular insecticides to two season nurseries at three monthly intervals. Application of granular insecticides at three monthly intervals is highly essential to protect the underground and sub-aerial parts in clonal nurseries.