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E. The Commercial Significance of K Buffer Power Determination in K Fertilizer Management for Perennial Crops

E. The Commercial Significance of K Buffer Power Determination in K Fertilizer Management for Perennial Crops

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THE AGRONOMY AND ECONOMY OF CARDAMOM



289



fertilizer prices by the Government of India resulted in an overnight escalation

of their market prices. In a situation like that, the farmers become extremely

wary of their field use and unless the fertilizer application is cost eVective, faith

in their use, especially those mentioned above, would be shattered.

The K fertilizer recommendation for cardamom has been based exclusively

on NH4OAc extraction. The investigation of Nair et al. (1997) showed its

ineVectiveness. Although the importance of K buVer power in predicting K

availability has been reported earlier, these research reports related to mainly

annual crops, such as white clover (During and Durganzich, 1979) and rye

grass (Busch, 1982); the work of Nair et al. (1997) was the first of its kind in a

perennial crop.

One last point regarding the question of accurately predicting K availability

is the role of NH4 ion on Kỵ ion. One of the frequent assumptions made in

predicting K availability in soils is that results from binary (two‐ion) exchange

systems can be extrapolated to ternary (three‐ion) systems by using appropriate

equations. The K–Ca exchange reactions in soils are often investigated in

laboratory studies. Most of the research carried out on soil clay minerals and

soils as exchanger surfaces (Argersinger et al., 1950; Gapon, 1933; Jardine and

Sparks, 1984; Sposito, 1981a,b; Sposito et al., 1981, 1983; Vanselow, 1932) are

binary exchange systems. However, field soils are at least ternary systems

(Adams, 1971; Curtin and Smillie, 1983). The evaluation of soils as binary systems implies that these reactions can be used to predict results in ternary

systems such as field soils. For this assumption to be valid, the binary exchange

selectivity coeYcients need to be independent of exchanger‐phase composition

(Lumbanraja and Evangelou, 1992). But, the work of Shu‐Yan and Sposito

(1981) showed that it is impossible to predict exchange phase–solution phase

interactions in a ternary system, such as the field soil from a binary system, such

as the laboratory sample. This focuses the importance of the ternary systems.

As far as K availability is concerned, it would be important to include NHỵ

4

ion as well. The work of Lumbanraja and Evangelou (1992) has shown that Kỵ

adsorption to soil surfaces is suppressed in the presence of added NHỵ

4 ion,

while the adsorption of NHỵ

ion

to

the

same

surface

is

enhanced

in

the

presence

4

of Kỵ ion. These observations point to the influence of added NHỵ

4 ion on

the desorption potential (chemical potential) of adsorbed K or vice versa

(Lumbanraja and Evangelou, 1992) and would be relevant to the determination

of K buVer power especially when agents containing NHỵ

4 ions, such as

NH4OAc, are used in determining K buVer power (Nair et al. 1997). The

work of Lumbanraja and Evangelou (1992), although, clearly demonstrates



the eVect of NHỵ

4 ion on K desorption, with an increase in K desorption in the

presence of added NH4 ion. In its absence, it might be safe to conclude that the

shape of the K buVer power curve will not appreciably change even if larger

quantities of K are removed due to cropping and therefore can be considered as

a relatively constant property of soils. There is evidence to support this view



290



K. P. PRABHAKARAN NAIR



(Jimenez and Para, 1991). These authors, while investigating the Q/I relationship with reference to K uptake by wheat (Triticum aestivum) in calcareous

vertisols and inceptisols of southwestern Spain, found that 80% of the K

extracted came from the nonexchangeable K pool. These observations coupled

with the one discussed earlier, suggest that the precision of predicting K

availability can be substantially enhanced by first quantifying the K buVer

power of the soil in which the crop is intended to be grown. Admittedly, the

rate‐limiting steps involved in the K dynamics are not entirely understood

(Sparks, 1987). Notwithstanding this limitation, if one must move forward in

devising better management of K fertilizers in crop production, a starting point

has to be made with regard to precisely quantifying K availability. Quantifying

the K buVer power of soils and basing K fertilizer recommendations on this

seems to be the best starting point. The investigations of Nair et al. (1997) in a

crop like cardamom, which is the second most important spice crop in the

world, shows clearly that this can be done.



F. CONCLUSIONS

Though cardamom is a perennial crop, its growth behavior resembles that

of a biennial crop in the sense that the vegetative phase (tiller production) is

preceded to the reproductive phase in the following year when panicle and

flower initiation is flowed by fruit set. Since cardamom grows in forest canopy

where shade trees also grow, competition for moisture and nutrients from the

shade trees should be expected and, hence, water and nutrient management

should be controlled intelligently. Following the oil crisis, fertilizer prices

have drastically escalated, and it becomes all the more important why economization and enhancement of eYciency of use are important. The relevance

of ‘‘The Nutrient BuVer Power Concept’’ is highlighted in this context.



VI. CARDAMOM PATHOLOGY

Cardamom plant is aVected by a number of pathogens, of which some are

fungi, others bacteria, and yet some others nematodes. These pathogens aVect

the plant both in the nurseries and main plantations. To date, as many as

25 diseases caused by these agents have been reported. On the basis of severity

of damage, these diseases are categorised as major and minor. Considerable

damage is caused by four major diseases in the plantations and two in the

nurseries. Major diseases, such as the rots, leaf blights, and nematode infestation, are often widespread and lead to crop losses, while minor diseases



THE AGRONOMY AND ECONOMY OF CARDAMOM



291



generally cause damage to the foliage. Unless properly managed, diseases can

cause up to 50% loss to the crop.



A. MAJOR DISEASES

Capsule rot (locally referred to as ‘‘Azhukal’’) and the rhizome rot are the

ones which cause the most severe damage. Leaf blight and nematode infection lead to weakening of plants and consequent reduction in productivity.

Table XXVII lists the major diseases.



1. Capsule Rot (‘‘Azhukal’’ Disease)

Capsule rot, locally known as ‘‘Azhukal’’ disease (in the South Indian

Kerala State, language Malayalam) means rotting. It is the most severe

fungal disease of cardamom. Menon et al. (1972) reported it for the first

time in the cardamom plantations of Idukki district in Kerala State.

a. Geographic Distribution of the Disease. Initially, rotting symptoms

are observed on the fruits or capsules, and that is the reason the disease has

been named as capsule rot. Subsequently, the disease symptoms are observed

in other plant parts. This is the major disease aVecting cardamom and

causing severe loss of productivity in Idukki and Wayanad districts of

Kerala State and Anamalai hills of Tamil Nadu (Thomas et al., 1989). The

disease appears following the onset of southwest monsoon. Capsule rot is

not observed in the low‐rainfall areas of Tamil Nadu. Surprisingly, although

Karnataka State receives much rainfall, the disease is still to appear in the

state.



Table XXVII

Major Fungal and Nematode Diseases of Cardamom

Disease



AVected plant parts



Causal pathogen



Capsule rot (‘‘Azhukal’’)



Capsules, leaves,

Panicles, young tillers



Rhizome rot (clump rot)



Rhizomes, tillers, roots



Leaf blight (‘‘Chenthal’’)

Root knot nematode



Leaves

Roots, leaves



Phytophthora meadii,

Phytophthora nicotianae var.

nicotianae

Pythium vexans,

Rhizoctonia solani,

Fusarium oxysporum

Colletotrichum gloeosporioides

Meloidogyne incognita



292



K. P. PRABHAKARAN NAIR



b. Symptoms and Damage. Disease symptoms develop mainly on

the capsules, young leaves, panicles, and tender shoots. The first visible symptom appears as discolored water‐soaked lesions on young leaves and capsules.

These lesions enlarge and the aVected portions decay. Infection occurs on

capsules and tender leaves simultaneously, or, sometimes first on capsules

followed by infection of foliage (Thomas et al., 1991a). When foliage is infected,

water‐soaked lesions appear on leaf tips or leaf margins, which subsequently

enlarge and adjacent lesions coalesce to form large patches. Immature unfurled

leaf when infected fails to unfurl subsequently. As the disease advances, the

lesions on the leaves turn necrotic, followed by leaf decay and shrivel, and

finally they look shredded. Infected capsules show water‐soaked discolored

patches. These turn brownish and later these infected capsules decay and

drop oV. Foul smell emits from such rotten capsules. Capsules of all ages

are susceptible to infection. However, young capsules are far more prone to

infection than older ones.

When favorable climate prevails, the disease is aggravated and infection

extends to panicles and tender shoots. In severe case of infection, the whole

panicle or psuedostem decays completely. In such cases the rotting extends

to underground rhizomes also. The root system of such plants gets decayed

and following this, the entire plant collapses to the ground. Nair (1979)

described similar symptoms and observed that the disease severity is uniform

in the three major cardamom types, namely, var. Malabar, var. Mysore, and

var. Vazhukka. Nambiar and Sarma (1976) who investigated the disease

have reported loss in productivity up to 30%. Subsequently, the loss has been

reported to be as high as 40% (Anon, 1989a).



c. Causal Pathogen. Phytophthora sp. as the causal pathogen of the

disease was first reported by Menon et al. (1972). Thankamma and Pillai

(1973) identified the organism as Phytophthora nicotianae Brede de Haan

var. nicotianae Waterhouse and Phytophthora palmivora Butler (Radha and

Joseph, 1974). Nambiar and Sarma (1976) reported the association of

Pythium vexans and a Fusarium sp. along with Phytophthora sp. However,

subsequent investigations (Nair, 1979) showed Phytophthora nicotianae var.

nicotianae as the causative pathogen, which was successfully isolated from

all infected plant parts. Phytophthora mediaii Mc Rae has also been widely

observed to cause the capsule rot disease (Anon, 1986). Host‐range studies

show that Phytophthora palmivora from coconut and rubber trees can infect

cardamom (Radha and Joseph, 1974). Also Phytophthora palmivora can

infect coconut, cocoa, arecanut, black pepper, and rubber (Manomohanan

and Abi Cheeran, 1984). Phytophthora meadii from cardamom can also

infect black pepper, cocoa, and citrus (Sastry and Hegde, 1987, 1989).



THE AGRONOMY AND ECONOMY OF CARDAMOM



293



Nair (1979) observed that wild colocasia plants in cardamom plantations

serve as collateral hosts for Phytophthora nicotianae var. nicotianae.

Based on culture characters, sporangial morphology, sexual behavior,

and pathogenic virulence, seven diVerent isolates of Phytophthora meadii

from diVerent localities causing infection on capsules, leafy stems, leaves,

and rizhomes have been identified (Anon, 1989a). These seven isolates fall

into two groups in their requirement for optimum temperature for growth

and mean sporangial dimensions. In single cultures no oospores are formed

but when paired with A 1 mating type, five of them readily formed sex

organs and oospores confirming that most of these isolates belong to the

A 2 mating type. The type species of Phytophthora meadii from cardamom

readily grows on carrot agar and sporulates; the sporangia are caduceus,

ellipsoid, papillate, and with short to medium pedicels. Although these seven

isolates morphologically diVer only slightly, all of them were found to be

pathologically virulent types. The pathogen, Phytophthora nicotianae var.

nicotianae survives in the soil and plant debris in the form of chlamydospores

and in moist soil up to 48 weeks (Nair, 1979). However, in the case of

Phytophthora meadii, no chlamydospore formation has been observed. The

inability of Phytophthora meadii to form chlamydospores from rubber is also

reported.

d. Epidemiology. The epidemiology of capsule rot disease has been

studied by Nair (1979). He observed that high disease incidence is correlated to

high and incessant rainfall during the southwest monsoon. The number

of Phytophthora propagules increases in soil and results in heavy disease incidence coinciding with high soil moisture levels (34.3–37.6%), low temperatures

(20.4–21.3 C), high relative humidity (83–90.6%) and high rainfall (320–400 mm

annual) during the months of June to August (Nair and Menon, 1980).

Presence of high level of soil inoculum, thick shade in the plantation, close

spacing, high soil moisture, water logging together with favorable weather

conditions, such as high relative humidity, continuous rainfall and low temperature predispose the plants to Phytophthora meadii infection. Nair (1979)

also observed that the density of Phytophthora population reduces with

increasing distance from the plant base and with depth from soil surface.



2.



Disease Management



Since the disease outbreak occurs in the monsoon season, the disease

management aspects have to be in place suYciently early, that is, prior to

the onset of primary infection. During earlier years various fungicides have

been extensively used to control the disease. Spraying and drenching of



294



K. P. PRABHAKARAN NAIR



copper fungicides, such as, 1% Bordeaux mixture, 0.2% copper oxychloride

(Menon et al., 1973; Nair, 1979; Nair et al., 1982; Nambiar and Sarma, 1974)

has been recommended as the disease control measure. Inhibition of the

fungus in vitro conditions has been reported following treatments with

organomercurials (Wilson et al., 1974). Nair (1979) observed 86% reduction in soil population levels of Phytophthora when drenched with 1%

Bordeaux mixture or 100 ppm Dexon (Bay‐5072). Alagianagalingam and

Kandaswamy (1981) observed that the disease could be controlled by spraying the plants with 0.2% Dexon (Bay‐5072) at the rate of 4 kg haÀ1.

Although a number of fungicides have been reported to control the disease,

often disease control in the field has been a challenging task. Factors

responsible for the constraints in achieving satisfactory disease control

include lack of adequate phytosanitation, eVective and timely application

schedules, high cost and nonavailability of fungicides, and the continuous

rainfall that makes spraying a diYcult operation and reduces its eYcacy

when the fungicide is sprayed.

Thomas et al. (1989, 1991a) evaluated a number of contact and systemic

fungicides under field conditions and concluded that two to three rounds of

sprays, including one round of prophylactic spray, with 1% Bordeaux mixture

or 0.3% Aliette (Fosetyl–aluminum) after proper phytosanitation eVectively

controlled the spread of the disease.



3.



Biological Control of Diseases



Bioagents play an important role in an ecofriendly system of disease

management to fight against plant pathogens in a totally safe manner

avoiding the use of expensive and hazardous chemical fungicides. Inhibition

of Phytophthora meadii in laboratory conditions and disease suppression in

cardamom nurseries have been investigated by Thomas et al. (1991b)

employing Trichoderma viride, Trichoderma harzianum, Laetisaria arvalis,

and Bacillus subtilis. Suseela Bhai et al. (1993) achieved field control of

capsule rot disease employing Trichoderma viride and Trichoderma harzianum and have developed further a simple carrier‐cum‐multiplication medium for Trichoderma sp. application in fields (Suseela Bhai et al., 1994, 1997).

Cardamom‐growing soils in their native state, which harbor Trichoderma

viride and Trichoderma harzianum isolates, have been screened and eVective

strains for high‐biocontrol potential have been developed (Dhanapal and

Thomas, 1996). Field control of capsule rot disease has become eVective,

environmentally safe, and economically cost eVective due to the biocontrol

potential of Trichoderma sp.



THE AGRONOMY AND ECONOMY OF CARDAMOM



4.



295



Rhizome Rot Disease



This disease is also known as clump rot. The onset of the disease occurs

during the southwest monsoon. Park (1937) reported the occurrence of the

disease for the first time. Subba Rao (1938) described the disease as clump

rot. The disease is widely distributed throughout cardamom plantations in

the States of Kerala and Karnataka and also in Tamil Nadu where heavy

rainfall occurs as in Anamalai hills.

a. Symptoms of the Disease. It is during the southwest monsoon, by

about the middle of June, that the disease makes its appearance. The first visible

symptom is the development of a pale yellow color in the foliage and premature

death of older leaves. These leaves show wilting symptoms. The collar portion

of the aerial shoots becomes brittle and the tiller breaks oV at the slight physical

disturbance. Rotting symptoms develop at the collar region, which becomes

soft and brown colored. At this stage the aVected aerial shoots fall oV emitting a

foul smell. Mayne (1942) reported the incidence of the disease in cardamom

hills of the State of Kerala. The tender shoots or the young tillers also turn

brown colored and rot completely. With the advancement of the disease, all the

aVected aerial shoots fall oV from the base. The panicles and young shoots

attached to this also are aVected by the rot. Rotting extends to the rhizomes and

also roots. Falling oV shoots resulting from rhizome rot infection becomes

severe during July–August. In severely aVected areas, as much as 20% disease

incidence is recorded.

b. Causal Pathogen. Subba Rao (1938) observed that cardamom rhizome rot is caused by Rhizoctonia solani Kuhn., and it was associated with

a nematode. Ramakrishnan (1949) reported Pythium vexans de Barry as the

causal pathogen. Thomas and Vijayan (1994) reported that Fusarium oxysporum is also occasionally found to cause rhizome rot and root infections.

c. Disease Management. The disease is usually observed in areas previously aVected by rhizome rot disease. Therefore, phytosanitation plays an

important role in disease management. Presence of inoculum in the soil and

plant debris, over crowding of plants, and thick shade are congenial conditions

for disease development. Therefore, any disease management schedule has to

be followed with these factors in mind. Application of superphosphate at the

rate of 300–400 g per plant has been recommended for controlling clump rot

in cardamom plantations (Anon, 1955). Soil drenching with 1% Bordeaux

mixture or 0.25% copper oxychloride or neem oil cake at the rate of 500 g per

plant followed by one round premonsoon and two rounds of postmonsoon soil

drenching with 0.25% copper oxychloride at an interval of a month has been

reported to be eVective for controlling the disease (Thomas and Vijayan, 1994).



296



K. P. PRABHAKARAN NAIR



d. Biological Control. Attempts in rhizome rot disease control, as in

the case of capsule rot, are by taking recourse to the use of Trichoderma sp.,

namely, Trichoderma viride and Trichoderma harzianum (Thomas et al.,

1991b). A formulation of Trichoderma harzianum in a carrier medium consisting of farm yard manure and coVee husk mixture has been developed for

field application in the integrated disease management system for the control

of rot diseases of cardamom (Thomas et al., 1997).

5.



Leaf Blight Disease (‘‘Chenthal’’ Disease)



Chenthal is a leaf blight disease and the name is colloquial (Malayalam

language of the State of Kerala, meaning shredding). The disease was first

reported by George et al. (1976) from Idukki district of the State of Kerala.

Since then the occurrence of the disease has been observed in many plantations. The disease spread is faster in partially deforested areas and less

shaded plantations. Although it was reported as a minor disease of limited

spread, presently the situation is alarming as the disease is spreading to

newer areas and is becoming a major problem.

a. Disease Symptoms and Damage. Chenthal appears mostly during

the premonsoon period and the severity increases during summer months.

Symptoms develop on the foliage as water‐soaked rectangular lesions, which

subsequently elongate to form parallely arranged streaks. The length of these

streaks varies from a few millimeters up to 5 cm. The lesion areas become

yellowish‐brown to orange‐red in color and often the central portions become

necrotic. Usually the two youngest leaves are not attacked by the disease. As

the disease advances, more and more lesions develop on older leaves, adjacent

lesions coalesce, and these areas begin to dry up. Severely infected plants show

a burnt appearance. George and Jayasankar (1979) reported reduction in

plant height, panicle length, and crop loss due to failure of panicle formation

in severely aVected plants. However, Govindaraju et al. (1996) studied

the symptomatology in detail and found that Chenthal infection aVects only

the leaves and not the plant height, panicle emergence or crop yield.

b. Causal Pathogen. Chenthal was originally reported as a bacterial

disease caused by Corynebacterium sp. (George and Jayasankar, 1977).

They also recommended penicillin spray for controlling the disease. As later

investigators could neither isolate Corynebacterium sp. nor control the disease

with penicillin sprays, the bacterial etiology was suspected, and the cause of

the disease remained obscure for more than a decade. Govindaraju et al.

(1996) conducted detailed investigations on symptomatology, etiology, and

management strategies of Chenthal and have clearly shown beyond doubt



THE AGRONOMY AND ECONOMY OF CARDAMOM



297



that the causal pathogen is the fungus Colletotrichum gloeosporioides (Penz.)

Penz and Sacc. The fungus closely resembles Colletotrichum gloeosporioides

causing anthracnose disease of capsule rot reported by Suseela Bhai et al.

(1988). Both the leaf and capsule isolates showed similar cultural and morphological characters and were cross‐infective to capsules and leaves and vice

versa. However, these two isolates exhibited considerable diVerences in their

period of occurrence, type of symptoms, distribution and spread of the

disease.

c. Disease Management. Since the disease was considered to be caused

by Corynebacterium sp., penicillin spray was suggested as a control measure

for the disease (George and Jayasankar, 1977). However, this was not eVective and was abandoned by the planters. Govindaraju et al. (1996) reported

that three sprays of Carbendazim (Bavistin, 0.3%) at monthly intervals, or

Mancozeb (0.3%) or copper oxychloride (0.25%) eVectively controlled the

spread of Chenthal disease in the cardamom plantations.

d. Diseases Caused by Nematodes. Heavy loss of the crop could be

brought about by nematode infestation. Although as many as 20 diVerent

genera of plant parasitic nematodes have been reported in cardamom‐growing

soils (Ali, 1983), only the root knot nematode (Meloidogyne incognita), the

same which attacks black pepper as well (Nair, 2004), causes the most damage

to cardamom. Root knot nematode is widely observed in almost all the cardamom grown regions, both in the nurseries and main plantations (Ramana

and Eapen, 1992), while the lesion nematode (Pratylenchus coVeae) and the

burrowing nematode (Radopholus similis) are observed in mixed plantations.

e. Disease Symptoms and Damage. Aerial plant part damages, such as

stunting, reduced tillering, resetting and narrowing of leaves, yellow banding of

leaf blades, and drying of leaf tips or leaf margins are noticed. The flowering is

normally delayed. Immature fruit‐dropping results in yield reduction (Anon,

1972, 1989b). Underground symptoms develop on the roots of infected plants

in the form of pronounced root galling. Tender root tips show spherical–ovoid

swellings. Severe infestation can result in crop losses up to 80% (Ramana and

Eapen, 1992). Nematode population is high in cardamom soils during postmonsoon period (September–January). Heavy shade in plantations, moist soil,

and warm humid weather are predisposing factors for nematodes to multiply.

Nematode infestation is a chronic problem in cardamom nurseries, where the

same site is repeatedly used for raising seedlings. Nematode‐infested soils aVect

seed germination and result in severe galling of the root system, marginal

yellowing, and drying of leaves, stunting and reduced tillering. The leaves

become narrow, and the leaf tips show upward curling.



298



K. P. PRABHAKARAN NAIR



f. Nematode Control. As infected seedlings serve as the source of inoculum, extreme care has to be taken in transplanting aVected seedlings, preferably, avoided as it would be the start of new infection. Pretreatment of

infested nursery beds with methyl bromide at the rate of 500 g/10 m2 or soil

drenching with 2% formalin is usually recommended. Solarization of nursery

beds is reported to reduce nematode populations in the soil. Nematicides,

such as Adicarb, Carbofuran, or Phorate, at the rate of 5 g active ingredient

(a.i.) per plant twice a year has been recommended for controlling nematodes

in plantations (Ali, 1984). A biocontrol schedule employing Trichoderma

viride or Trichoderma harzianum isolates and also Pacilomyces lilacinus

to control ‘‘Damping OV’’ disease and nematode damage in cardamom

nurseries has been put in place (Eapen and Venugopal, 1995).



B. MINOR DISEASES

A number of minor diseases, which aVect leaves, capsules, and aerial

stems, occur sporadically in cardamom plantations. Some of these are

frequently observed in all areas, while others are restricted to specific localities. These include various types of leaf spots and capsule spots, stem

infections, and so on, caused predominantly by fungal pathogens. Details

are given in Table XXVIII.



1.



Leaf Blotch



Agnihothrudu (1968) reported a foliar disease in cardamom characterized

by the typical blotching of leaves. The disease appears during monsoon

season, from June to August, normally under heavily shaded conditions.

Thick shade, continuous rainfall, and high atmospheric humidity predispose

the cardamom plants to infection. Leaf blotch was thought to be a minor

disease. Recently, however, it was found to spread in great severity in certain

regions.



2.



Disease Symptoms



Nair (1979) has studied in detail symptomatology of leaf blotch. During

monsoon, round ovoid, or irregular water‐soaked lesions appear on middle

leaves, usually near the leaf tips or at the midrib areas. These areas enlarge in

size, become dark brown with necrotic center. In moist weather, a thick,

gray‐colored fungal growth is seen on the under side of these blotched areas.

However, the lesion spread is limited in size following a dry period.



THE AGRONOMY AND ECONOMY OF CARDAMOM



299



Table XXVIII

Minor Fungal and Bacterial Diseases in Cardamom Plantations

Disease



The aVected plant part



Causal pathogen



Leaf blotch

Phytophthora leaf blight

Phytophthora leaf rust



Leaves

Leaves

Leaves



Phytophthora leaf spot



Leaves



Sooty mould

Stem lodging

Anthracnose

Capsule tip rot

Fusarium capsule rot

Capsule canker

(Vythiri spot)

Capsule ring spot

Bacterial rot



Leaves

Pseudo stem (tillers)

Capsules

Capsules

Capsules

Capsules



Phaeodactylium alpiniae

Phytophthora meadii

Pbakospora elettariae

(Uredo elettariae)

Sphaceloma cardamomi,

Cercospora zingiberi,

Glomerella singulata

Phaeotrichoconis crotalariae

Ceriospora elettariae

Trichosporiopsis sp.

Fusarium oxysporum

Colletotrichum gloeosporioides

Rhizoctonia solani

Fusarium moniliformae

Bacterium (?)



Capsules

Rhizomes



Marasmius sp.

Erwinia chrysanthimi



3.



Causal Pathogen



Leaf blotch is a fungal disease caused by Phaeodactylium venkatesanum

(Agnihothrudu, 1969). Subsequently this fungus was identified as Phaeodactylium alpinae (Sawada) (Ellis, 1971). The pathogen grows profusely on the

underside of the leaves and also grows abundantly on potato dextrose agar

medium. Hyphae are hyaline, smooth, partially submerged, 6–10 m thick,

dichotomously or often trichotomously branched with conidia formed at

their tips. Conidia are solitary, hyaline with three transverse septa, smooth,

elliptical with tapered basal end and broad apices. Conidia measure 15–25 m Â

4.7 m. The pathogen infects and produces typical symptoms on Alpinia sp.,

Amomum sp., and it has been observed that the fungus was completely inhibited

in vitro conditions by 1% Bordeaux mixture, 0.1% Bavistin, or 0.15% Hinosan

(Nair, 1979). Fungicidal spray with copper oxychloride or Bordeaux mixture

was reported to control leaf blotch infection in the field (Ali, 1982).



4.



Phytophthora Leaf Blight



In many cardamom plantations during the postmonsoon season, a widespread leaf blight disease is observed. The infection starts on the young‐middle



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