Technology that produces insecticide-free vegetables
K.S. Chawla
THE Department of Vegetable Crops, Punjab Agricultural University, has developed net-house technology for the cultivation of vegetables. These vegetables will be insecticide-free under this new technology which is an alternative to the green-house technology. The net-house technology is used in foreign countries and is quite costly compared to the green house technology.

Farm operations for MAY

Bordeaux mixture: panacea for disease
control in fruit plants
J.S. Dhiman

Discovery of Bordeaux Mixture
How to deter schoolboys from pilfering their grapes had been a problem of French farmers in the Modoc region for a long time. A poisonous looking mixture of lime and copper sulphate that struck tenaciously to the leaves when sprinkled on vines near road sides was the answer. Pilferage was not the only problem of the grape growers, for mildew (mildiou as they called it) disfigured and defoliated the vines in early fall every year. Prof P.M.A. Millardet of the University of Bordeaux was deputed to study the disease introduced from America. Once in 1882 while walking through the Medoc countryside he noticed significantly less mildew on the sprinkled vines. It looked as if the cure for pilferage was the cure for mildew too. Prof Millardet and his chemist colleague U. Gayon in 1885, after several spraying experiments, concluded that the mixture of copper sulphate and hydrated lime could effectively control the downy mildew of grapes. This mixture became known as "Bouillie Borde laise" — Bordeaux mixture — and its success in controlling downy mildew and many other foliage diseases was spectacular. This accidental discovery of the Bordeaux mixture gave a great stimulus to the study of nature and control of plant diseases. The virtues of the Bordeaux mixture were soon demonstrated against several diseases of bacterial as well as fungal origin in due course of time. Even today it is the most widely used copper fungicides all over the world. The Bordeaux mixture is very effective in controlling several diseases of fruit crops (Table 1). The growers can themselves prepare and use the Bordeaux mixture in their orchards.

Preparation of Bordeaux mixture
The Bordeaux mixture can be easily prepared by mixing copper sulphate solution and quick lime suspension in a fixed ratio (2:2:250) i.e. copper sulphate (2kg), quick (unslaked) lime (2 kg) and water (250 litres). The raw materials should be of good quality. Copper sulphate (98 per cent purity) and the freshly stocked lime stone (quick lime) should be obtained.

For preparing the 2:2:250 Bordeaux mixture, dissolve 2 kg of copper sulphate in 125 litres of water. Copper sulphate dissolves slowly in cold water. Hence, in winter it is better to use hot water or suspend copper sulphate in a muslin cloth bag into a non-metallic vessel (wooden barrel or earthen pitcher) so that the material gets dissolved in water and solid impurities, if any, are left out.

Slake 2 kg quick lime in another vessel (earthen or metallic). Avoid plastic container for this purpose. Add some water to the lime to make a paste to which water should be poured slowly to make the volume to 125 litres. Stir vigorously to make a lime suspension.

Mix the copper sulphate solution and lime suspension by pouring them together in the third vessel constantly stirring the mixture with a wooden stick while pouring. The lime solution should be poured through a strainer to keep back all lumps. A light blue liquid is obtained which should be strained through a muslin cloth or sack before putting in spray tank.

Uses of Bordeaux mixture
The application of the Bordeaux mixture has been recommended for the control of a range of fungal and bacterial diseases such as leaf spots, blights, anthracnose, downy mildew and cankers etc. It, however, causes burning of foliage or russetting of fruits such as apple when applied under extreme weather conditions. The phototoxicity of the Bordeaux mixture is reduced by increasing the ratio of lime to pathogens, and sometimes to plants, while lime primarily acts as a neutraliser. The Bordeaux mixture also acts as pit disinfectant in root/collar rot infested sites before planting new saplings in orchards. When used as a basin drench treatment it controls the spread of root rot pathogens from diseased plants to healthy ones. It renders protection to pruning cuts or injuries caused to the spurs during harvesting when used as a prophylactic treatment.

Test Bordeaux mixture before use
Performing any of the following tests can test the safety of the Bordeaux mixture:

Litmus test: The Bordeaux mixture is alkaline in reaction as it contains more proportion of lime. It should, therefore, turn red litmus paper blue. An excess of copper compound in the mixture may be dangerous to foliage of many plants and is indicated by solution turning blue litmus paper red.

Copper deposition test: It is a simple and practical way of estimating whether or not the mixture contains excess of copper in it. Immerse a bright iron surface such as knife blade or a nail in the upper layer of the liquid for a few minutes. A brick red or bright pink coppery deposit on the metal surface indicates the presence of excess copper and as such the solution is unsafe for use. Therefore, more lime solution should be added to the mixture and the test repeated till no such deposit appears on the clean metallic surface.

Reagent test: A more precise chemical test may be performed using the reagent, potassium ferrocyanide. The reagent may be obtained from a scientific chemical store. A few drops of the Bordeaux mixture are added to little of this reagent in a saucer. If no change occurs, the mixture is safe for use but its turning reddish brown, indicates the presence of excess free copper in it, which is not desired.

Some do’s and don’ts

• Use the Bordeaux mixture soon after preparation. If should not be stored for further use.

• Do not use metallic containers for preparing copper sulphate solution and lime suspension. Use a wooden stick for stirring to get a homogenous mixture. Never use metallic stick.

• Do not use the Bordeaux mixture in combination with any other chemical or pesticide e.g. in citrus, zinc sulphate spray should be given, keeping a gap of at least one week from that of the Bordeaux mixture.

• To avoid choking of the nozzle, it is advisable to strain the Bordeaux mixture through a cloth or a sieve before putting it into the spray tank.

• The Bordeaux mixture tends to sediment easily. Therefore, its stirring while using is desirable.

• It is not advisable to spray the Bordeaux mixture on fruit-laden trees as the spray may inflict russetting, especially on apple and pear.

• In exceptionally hot days, when the plants are showing signs of temporary wilting or when it is raining, the Bordeaux mixture should not be sprayed, particularly on newly emerged tender foliage. Exercise this caution particularly on nursery plants.

• After carrying out spray operations the appliances should be thoroughly washed with plenty of water to remove any copper deposits.

• The left over Bordeaux mixture should not be dumped in the field as this may prove toxic to the subsequent sowings.

Other formulations of Bordeaux mixture
Bordeaux paste: Pruning is a regular horticultural operation used of removing dead wood, diseased parts and to give shape to the fruit tree. It is undertaken annually during dormant period. The cut ends created during pruning need to be protected against infection by different pathogens, by sealing with suitable fungicide pastes. The Bordeaux paste is the most effective wound dressing material for this purpose. The fine layer formed on the cut ends kills the pathogen, if any protecting if from subsequent invasion and results in rapid healing of the wounds.

Application of the Bordeaux paste can effectively check the attack of collar rots and root rots of fruit trees.

Preparation of Bordeaux paste
The ingredients for the Bordeaux paste are copper sulphate (2 kg), quick lime (3 kg) and water (30 litres).

Dissolve 2 kg of copper sulphate in 15 litres of water. Slowly slake 3 kg of quick lime in a small amount of water. When slaked, add enough water to make the volume up to 15 litres. Thoroughly mix these concentrated solutions of copper sulphate and lime. This ready-to-use paste of sky blue colour is suitable for application to the cut ends with a brush.

Bordeaux paint
Bordeaux paint is applied for curing the deep and deformed wounds caused by cankers, gummosis, collar rot/root rot and to wounds resulting from surgical removal of crown gall or hairy roots from the stems of infected plants during dormant period. It is a suitable recommendation in areas or seasons which receive heavy downpour. It protects the treated part of the host against water for longer period, thus ensuring rapid healing of wounds.

Preparation of Bordeaux paint
To prepare the Bordeaux paint use monohydrated copper sulphate (1 kg), hydrated lime dust (2 kg) and boiled linseed oil (3 litres).

Monohydrated copper sulphate can be easily made by heating the copper sulphate crystals on an iron sheet or in a frying pan till they crumble into a white amorphous form which is ground into a fine powder. Monohydrated copper sulphate powder can then be mixed thoroughly with lime dust and homogenised with 3 litres of boiled but cooled linseed oil to make a thick paste. This paste may be stored in a glass jar or other suitable non-metallic vessel for future use. It can be applied to the plant parts with the help of a brush.

Technology that produces insecticide-free vegetables
K.S. Chawla

THE Department of Vegetable Crops, Punjab Agricultural University, has developed net-house technology for the cultivation of vegetables. These vegetables will be insecticide-free under this new technology which is an alternative to the green-house technology. The net-house technology is used in foreign countries and is quite costly compared to the green house technology. However, the results of the new technology are very encouraging and there can be an increase in the [production of vegetables by about 50 per cent and 100 per cent more than open cultivation.

According to Dr J.S. Hundal, Head of the Department of Vegetable Crops, the net-house cultivation was initiated under the guidance of Dr G.S. Kalkat, former Vice-Chancellor, in 2000. This is a very simple technology and a screen-like mosquito net is used to cover the field under which vegetables are grown.

Dr Hundal points out that under the present conditions, farmers are spraying a number of insecticides to save their crops from insect-pest and diseases. There is no law to check it and whatever vegetables come in the market are full of chemical residues which ultimately go into the human system and result in different diseases. The vegetables produced in the open are not fit for export. Therefore, the solution is net-house cultivation without the use of insecticides. Some net-house insects like mite and aphid can be controlled by non-insecticide like lime, sulphur or neam oils.

The Department of Vegetables has built up three net-houses to produce insecticide-free vegetables. A number of vegetables like tomato, brinjal, okra, capsicum, chilli and early cauliflower have been selected for net-house cultivation. The crops like brinjal, okra and tomato are highly prone to fruit borer and farmers have to spray a number of insecticides even double than recommended practices to control borer. The systemic insecticides like Rogour, Metasystoc and Pythroids are highly dangerous to human health. It is hoped to get borer-free brinjal, tomato and okra under net-house.

Dr Hundal says that the experiments have shown that the yield of vegetables is about 50 to 100 per cent more than open cultivation. Also vegetables take less time for ripening and the duration of fruiting period is likely to be extended. Net-house vegetables are likely to get a premium of 50 per cent in the market as compared to the open cultivation. The consumers will be ready to pay more for insecticide-free vegetables. The net-house system saves the plants from different storm, direct rain and wind which have great effect on plant growth in the open cultivation. Good results have been achieved in high-value crops like Shimla mirch which was planted in November and the first picking was done in February when the price of fruit was quite high.

— Control weeds in the plant as well as ratoon crop by giving hoeings with bullock-drawn plough or tractor-drawn implement. Due to the prevailing hot weather conditions, the sugarcane crop requires frequent irrigations at eight to 10 days’ interval. Apply 65 kg of urea per acre to the ratoon crop. Moisture conservation may be done by spreading mulch in between the cane rows. Use rice straw/wheat straw/rice husk for mulch. This also checks the growth of weeds.

— For checking attack of black bug, spray 350 ml of Thiodan 35 EC or Dursban 20 EC in 200 litres of water. Direct spray material into the leaf whorl.

— Sugarcane mite can be checked by spraying 400 ml of Malathion 50 EC in 100 litres of water per acre. Destroy baru weed growing nearby which is an alternative host for mite.

— The thrips also damage the sugarcane, particularly the ratoon crop, so spray the crop with 400 ml of Malathion 50 EC or 350 ml of Thiodan 35 EC per acre in 100 litres of water.

— Sometimes iron deficiency appeared in the ratoon and plant crops in the light-textured soils and calcareous soils. Deficiency symptoms first appear in young leaves as yellow stripes between green veins. Later the veins also turn yellow. To control this, spray the crop with 1 kg of ferrous sulphate dissolved in 100 litres of water on the foliage.

— After the harvest of wheat, the bunch variety SG-84/M-522 can be sown up to the first week of May after applying rauni irrigation. Whereas other varieties like M-355, M-522 of M-13 should be sown from May 25 onward with a pre-sowing with 5 g Thiram or 3 g of Indofil M-45 per kg of kernels.

— Apply 25 kg of CAN or 12 kg of urea and 50 kg of single superphosphate at the time of sowing. If the recommended dose of phosphorous has been applied to wheat, its application to groundnut can be omitted. However, under such situation application of 50 kg of gypsum would be required.

—Summer moong is severely attacked by thrips, which are small, dark brown, round in flowers and cause flower drop, deformation of pods, deterioration of grain quality and ultimately heavy reduction in yield. Spray the crop bud initiation stage with 100 ml Rogor 30 EC (dimethoate) or malathion 50 EC or 120 ml metasystox 25 EC (xydemeton methyl) in 100 litres of water per acre.

— Last irrigation to summer moong should be stopped 50-55 days after sowing. This would help in uniform ripening of the crop.

Due to prevailing hot weather conditions, sunflower would require irrigation at 8-10 days interval during this period. Various types of caterpillars such as Cabbage semilooper, Tobacco caterpillar and hairy caterpillars feed on green leaves and defoliate the attacked plants. These larvae can be checked by spraying 500 ml of Thiodan 35 EC or 200 ml Nuvan/Divap/Vapona 100 EC in 100 litres of water per acre. Repeat after two weeks, if necessary. This treatment will also control jassids and other sucking pests in case they appear.

— Progressive Farming, PAU