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Most important diseases of pulse crops in Pakistan

A short duration crop and called "poor man's meat"

By M. Mithal Jiskani
Apr 23 - 29, 2001

The population of Pakistan is increasing very rapidly, hence, there is a dire need of increasing the production of food grains as well as other agricultural commodities, such as sugar, pulses, vegetables and fruits, needed for human consumption.

The quantity and quality of dietary protein are a major problem in most of the food deficient countries, including Pakistan. The scientists are engaged day and night, to solve the problem and find out the ways for growing more proteineous food. In this regard, animals and different pulse crops have drawn attention of human beings since long time. Nowadays, the meat, fish and eggs as well as pulses and vegetables are common in use, to fulfil the protein requirements. The beef, wheat and potatoes contain 16, 6.9 and one per cent proteins (Boris, 1985). Whereas, according to Bhatti and Soomro (1996), the pulses viz. gram or chickpea, mung bean or green gram, lentil, black gram or urd bean (mash), red gram or pigeonpea (arhar) and cowpea vary from 11-28 per cent proteins according to variety (See Table).

Table: Seed composition (percentage) of different pulse crops grown in Pakistan.

Crop

Protein

Carbohydrates

Fat

Gram

21.1

61.5

4.5

Lentil (Masoor)

25.0

60.0

-

Mung bean

20-26

-

0.5-1.5

Mash

24.0

60.0

1.3

Red gram (Arhar)

28.0

-

-

Cowpea

23.4

60.3

1.8

The pulses are called "poor man's meat", due to their protein value. Pulses are also known as short duration crops. All pulses require very little amount of water, hence are termed as dry crops. Another advantage in the cultivation of pulses is that, all pulses play an important role in crop rotation, due to help in maintaining soil fertility, through atmospheric nitrogen fixing bacteria.

The major pulse crops of Pakistan are gram, field peas, green gram, lentil, black gram etc. The red gram and cowpea are grown on a small scale. There are many constrains, including the heavy losses, caused by a number of diseases to, the pulse crops in Pakistan. The most destructive diseases are caused by fungi, bacteria, viruses and nematodes. The losses due to the diseases to pulse crops are estimated from 4 to 44 per cent, depending upon the crop variety (Bashir, 1988). The diseases attracted attention after severe epidemic years, during which the diseases drastically reduced the total production. In view of the fact, the government realized need to import large quantities of pulses at a heavy cost of foreign exchanges. The diseases, therefore have the capacity to cause heavy losses both in volume in commodity and to farmer's income (Hafiz, 1986).

A brief account of the most important diseases of pulse crops in Pakistan, including the causes, symptoms, perpetuation, preventive and curative control measures of very destructive diseases, are cropwise discussed, which are responsible for reducing overall production to a great extent in some areas, in some years, and generate great concern because of their effects on the quality and/or quantity of the crop produce.

It must be kept in mind that wilt and blight diseases are reported as most destructive diseases in all pulse crops. These diseases are discussed in gram, only to avoid the repetition.

Gram or Chickpea: The gram (Chickpea, Bangal gram or Garbanzo) ranks' first as a pulse crop in the country being followed up by green gram only in area and production. Actually, the gram is almost only the rabi pulse-crop, that successfully grown in the vast barani areas after rain, kacha after floods and under dobari conditions just after the harvest of the rice crop, without irrigation water. In case of irrigated crop, only one irrigation found enough at flowering stage.

The crop suffers from a number of diseases, but wilt and blight reducing considerably the yield as well as the quality.

Wilt (Caused by Fusarium oxysporum f. sp ciceri)

Symptoms: The plants start wilting and ultimately dry up at seedling and/or at flowering stage. The diseased plants are pulled out easily, due to the loss of rigidity. Sometimes, sudden drooping of leaves and/or only a few branches of a single plant are affected. The disease mostly spreads in patches, but entire field may also be affected in severe conditions. Severe damage has been reported during early pod filling.

Perpetuation: The disease causing fungus may survive and carried over from year to year by sowing infected seed, while the diseased plant debris lying in the field or in the threshing area also helps the fungus to remain alive.

Control: Cultivation of disease resistant variety is only the most easy, economical and safe method. However, following measures could be beneficial if applied.

•Avoid the cultivation of gram in the diseased area for three years.
•Improvements of soil condition with good drainage minimize the disease incidence.
•Use of disease free seed or seed treatment with suitable seed dressing fungicides before sowing.
•Late and deep sowings reduce the incidence of the disease.
•Mixed croppings of gram with wheat, barley, rape, mustard, safflower, sorghum and millet help to check the disease.
•Diseased plants should be uprooted from the field and burnt. Avoid the making of bhusa stacks in the field.
•Sweeping the threshing floor and burning or burying all plant debris.

Blight [Caused by Mycosphaerella rabiei (Ascochyta rabiei)]

Symptoms: The disease starts from the base of the plant, which result in the death of the whole plant. The infected plants could not be differentiated in early stages from the distance. The affected plants may show partial or total drying, with purple to dark brown spots of different sizes on stems, branches, leafstalks and leaflets. These spots become brown to black lesions and affected plants or plant parts show burnt appearance. Primarily individual infected plants may be observed scattered but later on the disease appear in circular patches and ultimately the entire field come under attack, therefore, whole crop may be destroyed completely. The disease symptoms may also occur on the pods and seeds. The pods produce blackish spots while the seeds become shriveled.

Perpetuation: The disease causing fungus is a soil borne and can remain viable for considerable periods. Seed may also help fungus to survive.

Control: The control measures are same as suggested for wilt of gram.

Mung, Moth and Mash: Mung, moth and mash are also subjected to a number of diseases, but following are considered very common and very destructive.

Cercospora Leaf Spot (Caused by Cercospora canescens and C. cruenta)

Symptoms: The spots appear on leaves, gray to brown in colour and circular to irregular in shape. These spots increase in number and size, which turn into lesions of a reddish brown margin. The size of pods and seed is reduced, hence yield decreased considerably.

Perpetuation: The disease causing fungus is seed borne.

Control: The control measures are same as recommended for the wilt of gram.

Root and Stem Rot (Sometimes known as charcoal rot, caused by Macrophomina phaseolina, Rhizoctonia bataticola and R. solani)

Symptoms: The disease is difficult to identify in initial stages. However, dark lesions are formed on the main stalk near soil level, forming localized dark green patches. The tissues of the affected portions become weak and shredded easily. If the plants will pull out, the basal stem and root may show dry rot symptoms.

Perpetuation: The disease causing fungi are soil borne and remain viable for long period.

Control: The control measures are same as recommended for the wilt of gram.

Anthracnose (Caused by Colletotrichum lindemuthianum or
Gloeosporium phaseoili)

Symptoms: All the aerial parts of the plants are infected by the disease causing fungus. Initially, small spots appear in scattered manner but later on they coalesce, giving rise to broad lesions, which become dead. The spots are usually depressed with dark centre and bright red or orange margins. Sometimes, such lesions are seen lenticular to circular sunken and tan to brown.

Perpetuation: The disease is seed borne, but secondary spread takes place by air borne.

Control: The disease could be controlled by spraying suitable fungicides, but the suggestions given for the control of gram wilt may also found fruitful.

Attention!: It must be remembered that wilt and blight diseases are also most common and cause considerable loss to mung,. moth as well as mash crop. The symptoms, perpetuation and control measures for these diseases are same as described in wilt and/or blight of gram.

Lentil or Masoor: Likewise wilt and blight diseases are common, their symptoms, perpetuation and control measures are similar as that of wilt and blight of gram. While, another most important disease of lentil is described here under:

Collar Rot (Caused by Sclerotium roltsii)

Symptoms: The disease mostly appears at seedling stage and show rotting at ground level, leading to coller rot and death of seedlings, in small scattered patches or bunches. White thread like growth or mustard sized Sclerotia of fungus may also occur on ground.

Perpetuation: The disease causing fungus is soil borne.

Control: The control measures are same as suggested for wilt of gram.

References:

1. Bashir, M. 1988. Field crop diseases. CDRI, NARC, PARC, Islamabad.
2. Bhatti, I. M. and A. T. Soomro. 1996. Agricultural inputs and field crop production in Sindh. Agri. Res. Sindh, Hyderabad.
3. Bhatti, I. M. and M. M. Jiskani. 1996. Modern Agricultural Guide. Agri. Res. Sindh, Hyderabad.
4. Boris, A. 1985. A food beneficial to health. Sputnik, Moscow, Oct. 1985: 141-144
5. Hafiz, A .1986. Plant diseases. PARC, Islamabad.
6. Khoso, A. W. 1992. Crops of Sindh. 5th revised eddition.

The writer is Assistant Professor (Plant Pathology) Sindh Agriculture University Tandojam