MAM 051 Fundamentals of Agriculture Solved Question Paper June 2026 for IGNOU MBA (Agribusiness Management) and PGDAB

Q5. Pest epidemics and the factors behind pest outbreaks

Q5. Define pest epidemics. Analyze the factors responsible for the outbreak of pest epidemics.

Answer

Introduction

A pest is any organism that lowers the yield or quality of a crop: insects, mites, nematodes, rodents, weeds and disease-causing fungi, bacteria and viruses. In a balanced field ecosystem most pests stay at low, tolerable numbers because weather, natural enemies and host resistance hold them back.

Definition of pest epidemic

A pest epidemic, also called a pest outbreak, is a sudden and abnormal rise in the population of a pest over a large area within a short time, so that its damage climbs well above the economic threshold level and causes heavy crop loss. A build-up confined to a few fields is a local outbreak; one that spreads across districts, states or countries is an epidemic.

For plant diseases the term epiphytotic is also used. Well-known Indian cases include the 1943 Bengal famine, linked to brown spot of rice, the 2019 to 2020 desert locust upsurge in Rajasthan and Gujarat, and the arrival of fall armyworm on maize, first reported in Karnataka in 2018.

Factors responsible for pest epidemics

An outbreak happens when a susceptible host, a vigorous pest population and a favourable environment come together, and human practices often tip the balance. The factors fall into five groups.

1. Pest-related factors

• High reproductive potential and short life cycle, so several generations build up in one season (aphids, whiteflies, brown planthopper).
• Migration over long distances, as in locust swarms and planthoppers carried by wind.
• Introduction of new or invasive pests through trade and movement of planting material, where no natural enemies exist yet.
• Development of new biotypes and resistance to insecticides or to resistant varieties, for example pink bollworm resistance to Bt cotton seen in central and southern India from about 2015.

2. Host and crop-related factors

• Monoculture of one susceptible high-yielding variety over a large, continuous area.
• Continuous availability of food through multiple cropping and staggered, unsynchronised sowing, so the pest moves from one crop stage to the next.
• Lush, dense crop canopy that creates a humid microclimate inside the crop.

3. Weather and environmental factors

• Temperature, humidity and rainfall that suit pest breeding; warm, humid weather favours planthoppers and many fungal diseases, while dry spells favour thrips and mites.
• Unusual rainfall in breeding grounds, which produces vegetation and triggers locust multiplication.
• Mild winters that let more pests survive into the next season.

4. Faulty agronomic and chemical practices

• Excessive nitrogen fertiliser, which makes plant tissue soft and attractive to sucking pests.
• Indiscriminate and repeated pesticide sprays that kill natural enemies, leading to pest resurgence (as seen with brown planthopper in rice) and to outbreaks of secondary pests.
• Close spacing, no crop rotation, and poor field sanitation that leaves stubble, weeds and volunteer plants as alternate hosts.
• Expansion of irrigation without planning, which keeps fields humid for longer.

5. Weak monitoring and response

• Absence of regular pest surveillance, light traps or pheromone traps, so early build-up goes unnoticed.
• Delay in forecasting and in community-wide control, letting the pest spread from field to field.

Conclusion

Pest epidemics are rarely caused by a single factor. They follow when weather, host susceptibility and human practices all favour the pest. Regular surveillance, resistant varieties, balanced fertiliser use, conservation of natural enemies and Integrated Pest Management keep populations below the economic threshold and prevent outbreaks.

Q8. Drainage, its importance and the reasons for waterlogging

Q8. Define drainage. Explain its importance in agriculture. Analyze the reasons for water logging in farm lands.

Answer

Definition of drainage

Agricultural drainage is the removal of excess water from the soil surface and from the root zone, by natural or artificial means, so that the soil keeps the balance of air and water that crops need. Land is called waterlogged when the soil pores in the root zone stay filled with water and the water table rises close to the surface.

Drainage systems are of three main kinds: surface drainage through land shaping, field drains and open ditches; subsurface drainage through buried perforated pipes, tiles or mole drains; and vertical drainage, where tubewells pump out groundwater. Planting fast-growing trees to draw down the water table, called biodrainage, is also used.

Importance of drainage in agriculture

• Aeration of the root zone: roots need oxygen for respiration and nutrient uptake; saturated soil starves them of air.
• Better soil structure and workability: drained fields can be ploughed and sown on time, and heavy machinery does not compact them.
• Warmer soil: wet soil warms slowly, which delays germination and early growth.
• Control of salinity and alkalinity: drainage carries away salts leached below the root zone and stops the capillary rise of salty groundwater.
• Nutrient availability: it reduces loss of nitrogen through denitrification and keeps useful soil microbes active.
• Deeper rooting: plants root deeper when the water table is low, so they cope better with later dry spells.
• Fewer diseases and weeds: root rots and water-loving weeds decline once standing water is removed.
• Wider crop choice and higher yields: drained land can grow crops such as wheat, pulses and vegetables that do not tolerate wet feet, and even rice benefits from mid-season drainage.

Reasons for waterlogging in farm lands

Natural causes

• Heavy or prolonged rainfall that exceeds the infiltration capacity of the soil.
• Flat or saucer-shaped land with no natural outlet for runoff.
• Impermeable subsoil, a clay layer or a hardpan that blocks downward movement of water.
• A naturally high water table, as in low-lying and coastal areas.
• Floods and overflowing rivers or streams.

Causes created by human activity

• Over-irrigation and flood irrigation, applying more water than the crop uses.
• Seepage from unlined canals, distributaries and field channels; canal command areas in Punjab, Haryana and Rajasthan are well-known examples of waterlogging and secondary salinity.
• Irrigation projects built without a matching drainage network.
• Blocking of natural drainage lines by roads, railway lines, embankments and new settlements.
• Puddling for rice year after year, which forms a compact plough pan below the surface.
• Growing water-intensive crops such as rice and sugarcane on poorly drained soils.
• Poor maintenance of existing drains, which silt up or choke with weeds.

Conclusion

Drainage is as important as irrigation for sustainable farming. Lining canals, scheduling irrigation by crop need, keeping drains clean and installing surface or subsurface drainage where the water table is high protect soil health and keep land productive.