Everything you need to learn about vegetable cultivation, harvest and growth.
Although all plants are vegetables in a technical sense, the word “vegetable” generally refers to various edible plants, the different organs of which, such as roots, stems, leaves and fruits store reserve food material and are eaten either cooked or raw. The vegetables are an almost indispensable item of human diet and they play an important role in human nutrition.
The members of this group of plants have originated in different parts of the world, including India, and most of them are very old. Vegetables contain large amounts of water, the percentage varying from 70 to 95, and hence their food value is comparatively low. As sources of carbohydrate, they are next to cereals.
Carbohydrates are usually present in the form of starch and occasionally in the form of sugar and other substances. Besides carbohydrates, minerals, proteins, vitamins, etc., are present in different vegetables. The presence of indispensable mineral salts and vitamins are known to increase their nutritive value. Further, the roughages provided by the various plant tissues also help digestion.
Most of the vegetables are short-duration crops and can be grown in succession on the same plot of land. At present, the production and consumption of vegetables in India are quite inadequate, being only about 25 percent to 35 percent of the requirements. It is, therefore, essential to increase their production considerably in the country.
Greater attention should be paid to vegetables, not only because most of them grow quickly, take a short time to be ready for harvest and taste good, but also because they supply both basic and accessory nutrients and furnish maximum quantity of food from the area planted.
How to Cultivate Pumpkin, Cucumber and Gourds ?
While the pumpkin (Cucurbita moschala Duch. ex Poir) and the squashes (Cucurbita pepo L. and C. maxima Duch.) are believed to have originated in North and South America, the cucumber (Cucumis sativus L.) and gourds, namely, sponge-gourd (Luffa cylindrica (L) Roem.), ridge-gourd (Luffa acutangula Roxb.), ash-gourd (Benincasa hispida (Thumb.) Cogn.) and snake-gourd (Trichosanthes anguina L.) are in all probability natives of India.
In so far as the origin of bottle gourd (Lagenaria siceraria (Mol.) Standl.) is concerned, definite information is not yet available. The plant is found all over the tropics and subtropics of both the hemispheres. Bitter-gourd (Momordica charantia L.) is said to be a native of the tropical regions of the Old World.
An important characteristic of the gourds and pumpkins is their wide adaptability. They are grown in almost all the states of India. These vegetables are a rich source of carbohydrates, minerals and vitamins A and C. Some of them are used as ingredients of salad, some are used as pickles, some as conserves or sweets. The fibre obtained from sponge-gourd and ridge-gourd is sometimes used for domestic and industrial purposes. Pumpkin and bottle gourd are useful material for making some parts of stringed musical instruments.
All the above mentioned crops belong to the family Cucurbitaceae. The plants are herbs or shrubs, most of them being tendril-climbers. Stems hollow. Leaves are simple, alternate and palmately five lobed. In pumpkin, they are non-hirsute and soft textured, whereas in Luffa spp., they are smooth.
In bottle-gourd, leaves are sub-orbicular, cordate, non-lobed or slightly so and softly pubescent. In bitter-gourd, leaves are deeply lobed, and in ash ground and snake gourd, they are five angled. Flowers are unisexual, regular, pentamerous and epigynous. Stamens 5, connate. Carpels 3. Ovary inferior and ovules many. Fruit is fleshy, berry-like or pepo, varying in shape, colour, flavour and taste.
Climate:
While cucumber requires a short growing season and takes about 45 to 80 days from sowing to maturity, pumpkin and other gourds require a relatively long growing season and take 80 to 120 days. Rainy season is more favourable than the summer season in the case of cucumber, pumpkin and most of the gourds, whereas summer season is better for squashes. Winter squash does well under mild climatic conditions.
Soil:
These crops do well in different types of soils, ranging from sandy to moderately heavy, if the drainage is good. Soils, which are highly acidic or alkaline, are unsuitable for raising them.
Cultivation:
The cultural requirements of this group of crops are more or less similar. Pumpkin, cucumber and gourds are grown both in summer and in rainy seasons, whereas summer squashes grow well only in summer and winter squashes under mild climatic conditions.
In the plains, the summer crop is sown from January to March, and the rainy season crop in June-July. In the hills, they are sown in April. Two methods of sowing are commonly adopted. In one, properly spaced ridges are prepared and a number of seeds are sown on each ridge after manure has been added to it.
In the other method, seeds are sown on one or both sides of furrows made in the field. The distance between adjacent rows generally varies from 1,5 to 3 m, according to the crop, and the distance from plant to plant from 60 to 90 cm. About 2.5 to 3 kg of seed is required per hectare for sowing cucumber, 4 to 5 kg for gourds, and 7 to 8 kg for pumpkin and squashes.
These crops respond very well to manures and fertilizers. As is natural, doses of manures and fertilizers vary according to the type of soil, climate and the variety of the crop. General recommendations have been made in respect of different cucurbits. Farmyard manure may be incorporated in the soil at the time of land preparation, at the rate of about 30 tonnes per hectare.
Besides this, 80 kg of nitrogen and 50 kg each of phosphorus and potassium should be applied to increase the yield of the crop. Application of nitrogen should preferably be in two split doses, the first one at the vining stage and the other one at the initial fruit- setting stage.
The-field is to be kept free of weeds, particularly in the early stages of crop growth. Hoeing and weeding are done regularly so as to enable the plants to grow properly. After the vines are fully grown, only the large weeds are pulled out. In hot weather, the crop is watered every third or fourth day. In areas of high rainfall, the crop requires one irrigation in a fort-night, whereas in areas of low rainfall, one irrigation per week is required.
Harvesting and Yield:
For immediate use, the fruits are harvested when they are still tender. In cucumber, the proper stage of fruit harvest is judged by its size irrespective of its age. Fruits of different sizes are required for different purposes. Harvesting in the case of gourds is done at short intervals, when the fruits are tender. In bitter-gourd, the marketable stage of the fruit is reached in 12 to 15 days after pollination and harvesting is done at 4 to 5 days’ interval. Pumpkin and ash-gourd are harvested when the fruits are fully mature.
The average yields per hectare are 80 to 100 q in cucumber, 150 to 200 q in bottle gourd, 75 to 150 q in sponge and ridge gourds, 60 to 80 q in bitter gourd and squashes, 200 to 250 q in pumpkins, 100 to 300 q in ash gourd and 100 q in snake-ground.
Varieties:
Some of the recommended varieties are:
(i) Cucumber – Japanese Long Green, Straight Eight, China, Balam Khira, Khira Poona.
(ii) Pumpkin- Arka Chandan, IHR 83-1-1-LCo. 1.
(iii) Bottle-gourd– Pusa Summer Prolific Long, Pusa Summer Prolific Round, Pusa Meghdut, Pusa Manjari.
(iv) Sponge-gourd- Pusa Chikni
(v) Ridge-gourd- Pusa Nasdhar and Satputia
(vi) Ash-gourd- Co. 1
(vii) Bitter-gourd- Pusa Domausumi, Coimbatore White Long, Arka Harit, Kalianpur Baramasi
(viii) Summer Squash- Early Yellow Prolific, Australian Green, Butternut
(ix) Winter squash- Arka Suryamukhi
How to Cultivate Knol-Khol (Olkopi, Ganihigobi) ?
Knol-khol is believed to be a native of the coastal countries of northern Europe. It is a vegetable crop cultivated throughout India, more particularly in Punjab, Maharashtra and UP during the winter, as is the case with cabbage and cauliflower. It is primarily consumed after cooking and is rich in calcium, magnesium, potassium, phosphorus, sodium and sulphur. It also contains vitamins A and C.
Knol-khol (Brassica caulorapa L.) belongs to the family Cruciferae. The plant is herbaceous, the swollen spherical part of the stem, just above the ground, with prominent leaf scars, being the edible portion. It is an annual both in the plains and the hills for vegetable production and biennial in the hills for seed production.
Leaves are glaucous and glabrous, oval or oval-oblong, with the margins irregularly dentate. Inflorescence and flowers similar to those of B. oleracea. It is a cross-pollinated crop like cabbage and cauliflower with bisexual flowers.
Climate and Soil:
The climatic and soil requirements are more or less the same as those for cabbage.
Cultivation:
Knol-khol is a cool-season crop and is normally cultivated at the same time as cabbage and cauliflower. The seeds are sown in the nursery bed during the period from August to November and the seedlings are transplanted in flat beds in a well – prepared field, in rows running 30 cm apart with a plant to plant distance of 22 cm. The quantity of seed required for raising seedlings for one hectare is 860 g.
About 20 tonnes of farmyard manure should be incorporated in the soil at the time of land preparation. In addition to it, 50 to 60 kg of nitrogen, 80 kg of phosphorous and 40 kg of potassium per hectare should be applied before transplantation. A further dose of 50 to 60 kg of nitrogen should be applied as top-dressing about 6 weeks after transplanting, at the time of earthing up. Intercultural operations are the same as those for cabbage and cauliflower.
Harvesting and Yield:
Harvesting of the crop is done when the swollen edible portion of the stem attains the marketable size of about 5 to 7 cm in diameter and also develops a bright colour, i.e. when it is still tender and non-fibrous. This stage is reached in 1 to 1½ months after transplantation. The average yield ranges from 20 to 25 tonnes per hectare. Knol-khol can be stored for 2 to 3 days under ordinary conditions.
Varieties:
Some of the recommended varieties are- White Vienna, Purple Vienna, King of North and Kyote No. 3.
Seed Production:
The plant does not produce seeds in the plains.
Diseases, Physiological Disorders and Insect Pests (Cabbage, Cauliflower and Knol-khol):
Some of the common diseases are:
(i) Damping off caused by Pythium spp., Rhizoctonia spp., Fusarium spp., which can be controlled in the nursery by drenching the bed with 0.1% solution of Captan or Fytolon, by treatment of seed with Agrosan GN or Ceresan @ 2 kg per kg of seed.
(ii) Black rot caused by Xanthomonas spp. or Pseudomonas spp., which can be controlled to a great extent by adopting proper crop rotation and by hot water treatment of seeds at 48.9°C, for half an hour.
(iii) Leaf spot and blight caused by Alternaria spp., which can be controlled by hot water treatment as in the case of black rot.
(iv) Club root caused by Plasmodiophora, brassicae, which can be controlled by avoiding infected fields, by liming the soil and treating seedlings before transplanting with mercuric chloride solution (1 in 1500).
(v) Black leg caused by Phoma lingam, which can be controlled by proper rotation, seed treatment with fungicides and treatment with hot water.
(vi) Cabbage Yellows caused by Fusarium spp., for which no proper control measure is yet known.
Certain physiological disorders which commonly occur are:
(i) Whip-tail or extreme malformation of leaves and unsatisfactory curd formation, caused by deficiency of molybdenum, which can be controlled by the application of lime to acid soil and 1.2 kg/ha of sodium or ammonium molybdate.
(ii) Browning, common in cauliflower, in which the stem becomes hollow and the curd becomes brown, is caused by deficiency of boron and can be controlled by application of borax.
(iii) Buttoning which causes the development of small curd or button and is produced by the deficiency of nitrogen, can be avoided by proper fertilization.
(iv) Riciness, which appears when the harvesting of curds is delayed, causes elongation of the peduncle and also makes the curd granular and loose. This abnormality may be controlled by harvesting at proper time.
(v) Blindness, in which case the terminal bud does not develop and there is no curd or head and the leaves become large, dark green and leathery. Such plants should be removed from the field.
(vi) Root-knot nematode (Meloidogyne spp.), which can be controlled by practising proper crop rotation and also by fumigation of the soil with nematicides.
The commonly found insect pests are:
(i) Mustard saw fly (Athalia proximo), which can be controlled by spraying 0.02% Endrin or Malathion at fortnightly intervals.
(ii) Cabbage butterfly (Pieris brassicae), which can be controlled by hand picking of caterpillars and dusting 4% Carbaryl.
(iii) Semilooper (Plusia spp.), which can be controlled by the method adopted in the case of cabbage butterfly.
(iv) Diamond black moth (Plutella maculipennis), which can be controlled by dusting 4% Carbaryl or 1% Malathion.
(v) Aphids (Brevicoryne brassicae, Lipaphis erysimi), which can be controlled by spraying 40% nicotine sulphate or 0.05% Lindane.
How to Cultivate Pointed-Gourd (Patal, Palwal or Parwal) and Coccinia (Kundru) ?
Pointed-gourd (Parwal) and Coccinia (Kundru) are believed to be natives of India and both of them are relished as vegetables by a large number of people. While the pointed gourd is cultivated widely in the eastern part of the country, in the states of West Bengal, Assam, Bihar and UP, Coccinia is cultivated in the eastern as well as the southern parts.
As other cucurbitaceous vegetables, both pointed-gourd and coccinia have good contents of carbohydrates and vitamins A and C and are consumed after cooking. Pointed gourd is also known to be used in some sweet dish in certain states and the other as an ingredient of salad.
The two species, Trichosanthes dioica Roxb. (Pointed gourd) and Coccinia indica W. and A. (Kundru) belong to the family, Cucurbitaceae. The plant is a dioecious and semi- perennial creeper. Leaves are simple, alternate and petiolate; lamina cordate, ovate-oblong; basal lobes narrow, round at base in pointed-gourd and angular or lobed in coccinia. Tendril usually simple. Floral characters more or less like those of other cucurbitaceous vegetables described in the preceding paragraphs. Fruit is fleshy pepo, small round or thick; colour of skin green with or without white stripes.
Climate:
Both the species thrive well in warm and moist climate.
Soil:
The two crops prefer sandy loam and do not do well in heavy soils. As they are very much susceptible to water-logging, a good drainage is very necessary.
Cultivation:
Propagation of both pointed-gourd and Kundru is done from stem cuttings. In the case of the former, stem cuttings, each of about 60 cm length, are taken from one-year old fruiting vines of both male and female plants in October and put in sand in the nursery. Root-development takes place and the cuttings are transplanted in the field in 2 to 3 months.
Two different methods are adopted in planting the cuttings in the field:
(i) Straight vine method – The soil is prepared and mixed with farmyard manure. Long furrows of about 30 cm depth, are made and cuttings are planted in them cm deep at a distance of 2 m from end to end,
(ii)Ring method – In this method, cuttings are made into a ring and planted in hills, the distance between them being 2m × 2m.
In the case of Kundru, smaller stem cuttings are required for planting. Basins of 60 cm diameter are dug at a distance of 175 cm from one another and, in each of them, 2-3 stem cuttings of 12-15 cm length, as thick as a pencil and having 5-6 leaves, are planted about 3 cm deep. The planting of cuttings is done between July and February and the vines are later trailed on bowers. About 10% male cuttings are considered sufficient for pollination of female plants in an area of one hectare.
When the pointed-gourd is grown in river beds, no fertilizer is applied to it. In case the soil is not fertile, about 225 quintals of farmyard manure should be applied per hectare. So far as Kundru is concerned, 10 kg of farmyard manure is mixed with the soil up to a depth of 45 cm.
During the initial stage, careful hoeing and weeding are necessary. However, these operations become difficult after the vines trail on the ground and, under such conditions, removal of the big weeds by hand is only possible. Watering has to be done regularly until rains start.
Harvesting and Yield:
In both pointed-gourd and Kundru, fruit formation starts during March to June and the second flush appears with the rains. Fruiting continues till the month of October. As in other gourds, harvesting in both these crops is done when the fruits are tender and the seeds are immature.
The yield of pointed-gourd has been found to be relatively low in the first year, about 13 to 18 quintals per hectare, and in the next year, the same vine yields about 110 to 135 quintals. In case of Kundru, a maximum yield of 10 kg per creeper has been obtained.
Varieties:
No improved variety of pointed-gourd or Kundru has yet been recommended.
Diseases and Insect Pests:
Cucurbitaceous crops are attacked by a number of fungal diseases, the important among them being:
(i) Powdery mildew caused by Erysiphe cichoracearum and Sphaerotheca humuli, which can be controlled by growing resistant varieties or by spraying with 0.03% Karathane.
(ii) Downy mildew caused by P seudoperonospora cubensis, which can be controlled by spraying the crop with Bordeaux mixture or 0.2% solution of Diathane Z-78.
(iii) Fusarium root rot caused by Fusarium solani and F. cucurbitae, which can be controlled by hot water treatment of seed at 55°C for 15 minutes, followed by treatment with mercuric chloride and avoiding cultivation of cucurbits for three years.
(iv) Stem rot caused by Pellicularia rolfsii, which can be controlled by practising proper crop rotation.
(v) Mosaic caused by virus, which can be controlled by growing resistant varieties.
(vi) Anthracnose caused by Colletotrichum spp., which can be controlled by treating seeds with Agrosan GN and spraying 0.2% to 0.3% solution of Diathane Z-78.
Some of the common insect pests of cucurbitaceous crops are:
(i) Pumpkin beetles (Raphidopalpa foveicollis, R. intermedia and R. cincta), which can be controlled by collecting and destroying adults, by raking into soil 5% Aldrin against grubs, by dusting the leaves with 4% Carbaryl or spraying 0.05% Malathion.
(ii) Pumpkin caterpillar (Margaronia indica), which can be controlled by collecting and destroying caterpillars and pupae, and dusting 4%, Carbaryl.
(iii) Snake-gourd semi-looper (Plusia peponis), which can be controlled as No. (ii) above.
(iv) Bottle-gourd plume moth (Sphenarches caffer), which can be controlled as No. (ii) above.
(v) Pumpkin borer (Apomecyna pertigera), which can be controlled by cutting and destroying affected stems.
(vi) Fruit fly (Dacus spp.), the infestation of which can be minimised by baiting with Malathion and Protein hydrolyzate or by growing resistant varieties.
(vii) Epilachna beetle (Epilachna spp.), which can be controlled by spraying 0.1% Lindane W.P.
(viii) Jassids (Empoasca spp.), which can be controlled by spraying 0.1 percent Malathion.
(ix) Aphids (Aphis spp.), which can be controlled as No. (viii) above.
How to Cultivate Amaranthus (Natey, Chaulai) ?
Amaranthus is a very common leafy vegetable and is believed to have originated in India. It is widely cultivated in the plains of the country. It is cooked in the same way as spinach beet and is quite popular as a cheap and tasty vegetable. Besides being highly rich in vitamins A and C, it contains protein, carbohydrate and iron.
There are two common types of Amaranthus, Amaranthus tricolour L., which is known as “badi chaulai” and Amaranthus blitum L., which is known as “chhoti chaulai” and they belong to the family Amaranthaceae. The plant is an annual herb.
Climate:
Amaranthus is primarily a summer crop in the plains and grows well in warm weather. However, it thrives in the rainy season also.
Soil:
Loamy soil is most suitable for the crop although it can be grown in any type of soil. The crop cannot withstand water logging and, therefore, the field should be provided with proper drainage. The most suitable range of soil pH is from 5.5 to 7.5, but certain strains can grow well in soils with pH as high as 10.
Cultivation:
The crop is normally sown in the plains of north India in February or March in order to raise a summer crop. The sowing of the rainy season crop is done in June – July or when the monsoon starts. In southern India, where the climate is favourable, the crop can be sown any time of the year. The seeds are usually broadcast in flat beds. It may also be sown in rows running about 22.5 to 30 cm apart. Care should be taken to see that seeds are sown shallow, at a depth of about 1 cm. The usual seed rate is 1.5 to 2 kg/hectare.
Although this crop generally grows on the residual fertility of the soil, application of 25 to 30 tonnes of farmyard manure per hectare at the time of land preparation produces a good crop. The recommendations made in connection with fertilizer application are- 27 kg each of nitrogen and phosphorus and 54 kg of potash per hectare. The crop may be top dressed thrice with ammonium sulphate; the First dressing is given one month after sowing and the other two soon after the first and the second cuttings.
In case the moisture in the soil is insufficient at the time of sowing, a light irrigation should be given after the seed is sown. The crop should be irrigated during summer at intervals of 3 to 5 days. Weeding of the plot should be regularly done.
Harvesting and Yield:
Although the young seedlings are pulled out with roots, it is better to take periodical cuts, the first one 3 to 4 weeks after sowing and the subsequent ones at intervals of 8 days or so in Chhoti chaulai and, at intervals of 10 days, in Badi chaulai. The crop yields an average of 74 to 94 quintals of leaves per hectare.
Varieties:
Some of the recommended varieties are – Chhoti chaulai, Badi chaulai, Co 1.
Seed Production:
The crop is cross pollinated and hence a distance of about 400 m is maintained between two varieties for producing pure seeds. Being a quick-growing crop, seed formation takes 10 to 12 weeks only. Therefore, a few of the later cuttings are omitted to enable the plants to produce seeds in June.
Diseases and Insect Pests of Leafy Vegetables:
Some of the common diseases are:
(i) Leaf spot caused by Cercospora spp., which can be controlled by spraying Bordeaux mixture or 0.3 per cent Blitox, three times at fortnightly intervals.
(ii) Leaf spot caused by Cladosporium variable, which attacks only the prickly seeded varieties of spinach, can be controlled by the application of Bordeaux mixture or Cupravit.
(iii) Leaf spot caused by Phyllosticta spinacha, which is restricted to spinach beet, can be controlled by the application of Shell copper, Blitox or Cupramar, all of 0.3% concentration, at intervals of 2 to 3 weeks.
(iv) White rust caused by Albugo occidentalis and A. blightii, the former attacking spinach and the latter attacking amaranthus, which can be controlled by keeping the field and its surroundings clean, by crop rotation, and by spraying Bordeaux mixture.
(v) Downy mildew caused by Peronospora effusa, which attacks spinach, can be controlled by spraying 0.3% Diathane Z-78, three times at intervals of 15 days.
No serious insect pest of leafy vegetables has been reported. Aphids and caterpillars are, however, known to do considerable damage and may be controlled by Pyrethrins,. Malathion or some other suitable insecticides.
How to Cultivate Lettuce ?
Lettuce is a common salad crop, which has been under cultivation for at least 2000 years. It originated probably in Europe and Asia. The crop is grown in most of the states of India and is a rich source of vitamin A and minerals like calcium, phosphorus, sodium, sulphur, magnesium and potassium. It also contains vitamin C, proteins and carbohydrates.
Lettuce (Lactuca sativa L.) belongs to the family, Compositae. The plant is a herb and is an annual for leaf and head production and a biennial for seed production. Stem is short at first with a radical rosette of leaves. Later, a sparingly leafy flowering stalk is produced.
Radical leaves are 12.7 to 25.4 cm long, alternate, sessile or more or less clasping, nearly oblong, obovate or lanceolate, denticulate or pinnatifid. Inflorescence is an erect panicle, carrying a number of capitula, each with 12 to 16 flowers. Receptacle is flat and naked.
Corolla is truncate and 5 toothed. Anthers are sagittate at the base. Style is branches slender. Fruit is an oval, oblong or linear, flat achene, broadest towards the apex, carrying a pappus of fine silky hairs. The edible portion of the plant is the large-sized tender leaves. There are two general groups, one has open leaves and is known as leafy or “cutting” type, the other which looks like cabbage head and is harvested only once, is known as “head” type.
Lettuce, like cabbage and cauliflower, is a crop of the cool season. It does best if the range of monthly mean temperature during the growing season is from 12.8°C to 15°C. In high temperatures, leaves develop a bitter taste and production of seed stalk is accelerated.
Soil:
Sandy loam and silt loam, which are rich in organic matter, are very suitable for the crop. A soil pH of 5.8 to 6.6 is considered optimum.
Cultivation:
Sowing is done in the plains in September or October. Seeds are first sown in the nursery beds and, after a month or so, seedlings become ready for transplantation. The transplanting is done in well-prepared plots, in rows running 45 to 60 cm apart, the seedlings being kept at a distance of 30 to 45 cm. Sometimes the seedlings are transplanted on ridges.
With regard to manuring and fertilization, the common practice is to apply 18 to 36 tonnes of farmyard manure, 50 to 80 kg of nitrogen, 24 to 50 kg of phosphorus and 50 to 54 kg of potash per hectare. Farmyard manure may be applied at the time of land preparation and the complete dose of phosphorus and potash and half the dose of nitrogen just before transplantation. The remaining half of nitrogen may be applied as top dressing, about a month after transplantation.
Lettuce is a shallow-rooted crop and hence light tillage may be given. It needs fortnightly irrigations in the plains.
Harvesting and Yield:
Harvesting of leafy varieties is done when the leaves are immature and tender. So far as head varieties are concerned, the crop is harvested after it has attained a good size and more or less solid head. An average yield of 10 to 14 tonnes per hectare is obtained.
Varieties:
Some of the recommended varieties are-Great Lakes, Imperial 859 (both head types), Slow bolt, and Chinese Yellow (both leafy types).
Seed Production:
Though a self-pollinated crop, some amount of cross pollination is known to take place in lettuce and hence two varieties may be kept 50 m apart for pure seed production.
Diseases and Insect Pests:
Some of the common diseases are:
(i) Slimy soft rot caused by Erwinia spp., which can be controlled by the removal of the heads and also keeping the soil relatively dry.
(ii) Downy mildew caused by Bremia actucae, which can be controlled by spraying or drenching the young plants with Diathane or by growing resistant varieties.
(iii) Mosaic caused by virus, for which no control measure is known as such. It can, however, be controlled by eliminating aphids, which transmit the disease.
So far as insect pests are concerned, aphids (Aphis spp.) cause considerable damage and they can be controlled by the use of 3 to 4 percent nicotine dust if the temperature is around 18°C to 21°C. Malathion, Parathion or TEPP may also be used for controlling the insect.