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Most of the plant parasitic nematodes affect the root portion of plants except Anguina spp., Aphelenchus spp., Aphelenchoides spp., Ditylenchus spp., Bursaphelenchus cocophilus and B. xylophilus. Nematodes suck the sap of the plants with the help of stylet and causes leaf discolouration, stunted growth, reduced leaf size and fruits, lesions on roots, galls, reduced root system and finally wilting.

The nematode feeding on plant can be divided into above ground feeders and below ground feeders.

Sampling for nematode communities has been the basis for the development of appropriate control strategy. The major purposes of sampling for nematodes include population estimation for general detection, advisory or predictive programme, disease diagnosis and also for research purposes.

Plant parasitic nematodes cause serious problems in sustained crop production. For a successful management of nematodes, their morphology, biology and host - parasitic relationship should be thoroughly studied. A thorough study is achieved only when its taxonomical position is known. Thus, in a simple way taxonomy can be defined as the theroretical study of classification of an
organism.

Life cycle of nematode has six stages. The egg stage, first stage juvenile (J1), second stage juvenile (J2), third stage juvenile (J3), fourth stage juvenile (J4) and the adult stage.

Eventhough nematodes occupy nearly every habitat on earth, they are remarkably similar in morphology and life stages. Despite their structural complexity, certain basic principles are common to all nematodes. Nematodes are triploblastic, bilaterally symmetrical, unsegmented, pseudocoelomate, vermiform and colourless animals.

In light of the high population of nematodes, N.A. Cobb (1915) who is considered to be the father of American Nematology, provided a dramatic description of the abundance of nematodes. He stated, “if all the matter in the universe except the nematodes were swept away, our world still would be dimly recognisable.

Agricultural crops are being affected by a wide range of organisms such as insects, mites, fungi, bacteria etc. Another important and unseen enemy is known as plant parasitic nematodes. The study on nematodes is known as Nematology.

All varieties of rose are susceptible to this disease. It is an important disease of rose which causes a sharp reduction in number and size of fl owers.

The disease appears as tumour like swelling or galls on leaf veins, leaf stalks, peduncles, stems and on fruits. The galls on the vein give a swollen and hanging appearance to the leaves. These are elongated, looks glossy in beginning but later rupture to become rough and corky. When stems remain succulent, numerous tumours may form on them. In severe case, the plant may kill prematurely.

The symptom appears as numerous, circular, light yellow to dark yellow spots on both the surfaces of leaves but is more prominent on the upper surface. The spot may coalesce to form large, irregular patches and soon entire leaf turns yellow and dries. Affected leaves appear as reddish-brown in colour. Excessive spotting destroys green tissues and becomes weak and yield reduced drastically

It is known by different names such as Ramularia leaf spot, rust, bird’s eye spot, grey spots, and white spot. It mostly attacks leaves but can also attack fruit stalks and also fruits.

The fi rst symptom of disease appears in early spring soon after leaves come out of buds. Affected leaves become distorted and fold over as tips directed backwards. The whole lamina puckered except tip and blistered. In some leaves, part of leaf show distortion. Blistered portions are thicker, softer than the normal leaf blade. The affected areas remain green for a while and gradually become yellow and fi nally turn reddish-purple in colour. 

It is a serious disease of apple which not only reduces the quality and size of fruit but also cause premature fruit drop and defoliation. Fruit loses its marketability due to poor quality. It also reduces storage time and cause loss up to 70%.

The disease attacks all the growth stages of plant affecting all above-ground parts. Plant covered with powdery patches leads to distortion, malformation and discolouration of leaves especially young leaves. Powdery patches gradually turn to grey and fi nally dark colour. Affected fl ower fails to develop fruit. Young berries turn black, irregular in shape and develop cracks. Sometimes berries ripe partially and rot. Vines get wilted.

Citrus crop includes lime, lemon, sweet orange, mandarin orange, Kamala orange, grapefruit, malta and pomelo etc. The disease which attacks one species of citrus mostly attacks other species also.

It is a very common disease of mango. It is otherwise known as blossom blight, leaf spot, twig blight or wither tip.

It is a very important and commonly found disease of chili which observed in field as well as in storage. It is also known as anthracnose disease which is mostly seen in tropical and sub tropical regions.

It is a very common disease found in all the onion and garlic growing areas. It mostly attacks the bulb as well as the seed crop. The infection or severity of the disease is more in Kharif crop causing 60% yield loss.

Disease appears later part of the crop season mostly during blossoming period. The first sign of the disease is the appearance of small brown patches on the leaves mostly on basal leaves which starts from tip or margin of leaves and spread downwards or inward directions.

The disease is seen at 3-4 leaves stage. Scattered, irregular, yellowish patches appear on the upper surface of the leaves and stipules. On the corresponding under surface of these patches, a greyish violet fi ne cottony mildew growth is seen. Infected tissue soon dies and turns brown. The disease fi rst appears on lower leaves and later spreads to upper leaves.

The disease i s seen at all crop growing stages. The fi rst symptoms appear at the time of emergence of seedlings, when the cotyledons are attacked. They become yellow and turn brown followed by wilting and drying of the affected seedlings. In the fi eld, the wilting symptoms appear in patches. First of all, the older leaves become yellow, loose their turgidity, wilt, turn brown and droop.

Wilt appears in the fi eld as patches is both seedling stage and developed plants. Symptoms include drooping and wilting of uppermost leaves. Plants become completely yellow and die. Plants are affected during the pod fi lling stages, seeds are often shrivelled. There will be rotting at the basal portion of the plant. Discoloration of vascular bundle are noticed when the stem is spitted
open.

All the above ground parts of the plant are affected. There is development of round and elongated spots surrounded by brownish red margin on the leafl ets. At later stage spots coalesce and entire leaf turns brown. On green pods, the lesions are usually circular with dark margin and pin head like dark dots representing the pycnidia in concentric circles.

The initial symptom of Alternaria brassiciola appears as small, dark colored spots which enlarge rapidly to form circular lesions. Under humid conditions a bluish velvety fungal growth is seen in the centre of these spots. Spots caused by Alternaria brassicae are almost similar to those produce by Alternaria brassicicola but are comparatively smaller and lighter in colour. When many spots are formed on the leaves, the leaves turn yellow and dry prematurely. Formation of pods and seeds are adversely affected.

The plants wilt at the time of grain fi lling stage. A light brown water soaked area is seen at the stem base. Sclerotia can be seen on the outer region of stalk when the plants get older. White mycelial growth with large sclerotial bodies is seen over the stem pith. The stem often breaks down at the point of infection.

The disease was fi rst reported in Java in 1893 and is prevalent in all sugarcane growing countries. In India the disease occurs in an epiphytotic form in Uttar Pradesh and Bihar during 1939-1940 and 1946-1947 and cause severe damage that threatened the existence of sugar industries.

Loose smut of wheat occurs worldwide but is more abundant and serious in humid and sub – humid regions. In India, this disease is found in all wheat growing areas but the incidence is generally more in comparatively cooler and moist parts of north India than south India. The yield loss may go up to 30% due to this disease.

Over the period of time, the dairy sector has added distinct significance to growing Indian economy. India contributes nearly 19.54% to the global annual milk production with an impressive upliftment of 3.6% in yearly production rate as per the latest available data from FAO International.

So far we studied direct stress (Tensile or compressive) and tangential stress (shear stress) acting on plane individually. But in many engineering problems these both stresses are acts on a plane at a same time. In such cases resultant stress on that plane will be neither pure normal nor purely shear but there will be combined effect of normal and shear stress.

When any beam is loaded, stresses are induced and so to calculate those stresses, shear force and bending moment acting at load or support location must be required to calculate.

Thermal stress arises whenever there is some increase or decrease in temperature of a body which causes either expansion or contraction in the dimension of body. If body is free to expand or contract, with the rise or fall of temperature, there exist no stress in the body. But if deformation of the body is partially or completely resisted then stresses are set up in the body which is known as Thermal Stress. However amount of stress induced in partially prevented deformation will be small than in case deformation is totally prevented.

Whenever a thin hanging wire is loaded, it elongates and the load moves downwards. Increase in length of wire is governed by the magnitude of the load and nature of wire material. Experimentally it is found that the cohesive force between the molecules of hanging wire offers resistance against the deformation.

Mechanical power is usually transmitted from one shaft to another by using belts, ropes, chains, gears and clutches.

1. Belts and ropes are utilized if distance between the shafts is large. Belts and ropes are flexible and bend easily. But slip occurs between the belt and the pulley.

Machine: It is a device capable to doing work on application of some effort. Work done by machine is to raise load or to lower load or to do some other types of work like rotation of shaft.

Hydraulic pumps are the devices utilized to transfer pressure energy to liquids at the expense of electrical energy. The electrical energy is transferred to a motor which converts it into mechanical work and a pump is coupled to the shaft. The pump converts the mechanical energy to hydraulic or potential energy. 

Hydraulic turbines is a device which transforms the hydraulic energy or potential energy existing with the working medium to mechanical energy. The working medium is normally water which run the hydraulic turbine. The hydraulic energy is available with water by virtue of its height or altitude. The water which flow through the mountains is stored by constructing a dam or reservoir.

The internal combustion (I.C) engines are functioning on open cycle wherin the air is taken from the atmosphere and the exhaust gases are sent back in the atmosphere. The sequence of operation in a 4-stroke petrol and diesel engine involves Suction compression expansion and exhaust. The precise investigation of I.C engines are very complex due to open cycle system, the working fluid enter and leaves at different condition, quality of fuel and its combustion which make the task more difficult.

Heat engines - A device which change heat received by fuel combustion into mechanical work is called a heat engine. It may be classified into two broad categories viz. are Internal and external combustion engines.[8]

The application of (VCRS) Vapour compressor refrigeration system is in the air conditioners (window, split, central or precision), car air conditioners, domestic refrigerator etc. The different parts of a domestic refrigerator are: in the hermetical sealed compressor, air cooled condenser, capillary tube, thermo expansion device, filter, rotameter, solenoid valve, temperature control sensor.

A refrigerant is heat transfer medium through which phase change occurs from liquid to vapour i.e. evaporation at low temperature and pressure in the evaporator and then the phase change occurs from gas to liquid i.e. condensation at high pressure and high temperature in the condenser. The cycle of phase change of refrigerant, continues in the refrigeration system.

Refrigeration mean cooling i.e. lower the temperature by artificial means. It is a process of attaining lower temperature of the space or product below the surrounding temperature. It further involves maintaining the lower temperature achieved.

“Steam generator or boiler is, usually, a closed vessel made of steel. Its function is to transfer the heat produced by the combustion of fuel (solid, liquid or gaseous) to water, and ultimately to generate steam” [4] . The American Society of Mechanical Engineers (ASME) [5] gives the following definition of the steam generating unit:

Steam is utilized in steam power plants, steam engines, atomic power plant, and food industry for pasteurization, sterilization, textile industry, paper industry and in railway to generate power. Steam is also utilized in process type industries like sugar industries, textile industries, chemical industries for sizing and bleaching. Steam is also employed to store energy and transported through pipes.

Thermodynamics is defined as the “branch of science which deals with the interaction between the heat and work”[1]. Thermodynamics is also sometimes stated as the science of energy. Thermodynamic deals with the principles of energy and energy conversion in engineering. It also considers the thermodynamic properties of substances. Thermodynamics deals with the conversion of heat into work and vice-versa.

Integrated farming system is a multidisciplinary whole farm approach, which enables the farmers to identify opportunities and threats and act accordingly. It is a dynamic approach which can be applied to any farming system around the world. It is very effective in solving the problems of small and marginal farmers.

Conservation agriculture is an approach to managing agroecosystems for improved and sustained productivity, increased profits and food security while preserving and enhancing the resource base and the environment. Food and Agriculture Organisation of the United Nations defines conservation agriculture as a farming system that promotes maintenance of a permanent soil cover, minimum soil disturbance (i.e. no tillage), and diversification of plant species.

Low external input agriculture developed as a response to the criticisms surrounding Green Revolution technology being neither sustainable nor feasible for many small-scale farmers around the world. The concept aimed to redesign the agricultural system by optimising the use of biological resources, keeping changes to the natural ecosystem as well as the use of external inputs at a minimum (Pimentel et al., 1989).

The Green Revolution started in the early 1960s that led to the attainment of self-sufficiency in food grain production. This has been considered as the greatest agricultural transformation in the history of humankind. The Green Revolution contributed to widespread poverty reduction, averted hunger for millions of people, and avoided the conversion of thousands of hectares of land into agricultural cultivation.

The objective of any cropping system is efficient utilisation of all resources such as land, water and solar radiation, maintaining stability in production and obtaining higher net returns. The efficiency is measured by the quantity of produce obtained per unit resource used in a given time.