Major Crop Diseases and Their Management MCQs 2026

The causal fungus of wheat stem, leaf and stripe rust belongs to the genus

1. A Puccinia ✓
2. B Ustilago ✓
3. C Alternaria ✓
4. D Pythium ✓

Loose smut of wheat commonly becomes systemic when infection occurs during

1. A seed drying stage ✓
2. B flowering stage ✓
3. C grain storage stage ✓
4. D tillering stage ✓

Cotton leaf curl disease is mainly spread in the field by

1. A aphid ✓
2. B jassid ✓
3. C thrips ✓
4. D whitefly ✓

Bakanae disease of rice is characteristically associated with excessive seedling elongation due to

1. A gibberellin production by Fusarium fujikuroi ✓
2. B nitrogen toxicity in nursery soil ✓
3. C zinc deficiency in flooded soil ✓
4. D bacterial ooze in vascular bundles ✓

The common causal organism of rice sheath blight is

1. A Magnaporthe oryzae ✓
2. B Rhizoctonia solani ✓
3. C Xanthomonas oryzae ✓
4. D Ustilaginoidea virens ✓

False smut of rice is recognized in the panicle by

1. A white powder on leaf surface ✓
2. B black lesions on roots ✓
3. C greenish smut balls replacing grains ✓
4. D yellow streaks on stems ✓

Red rot of sugarcane is best identified in split canes by

1. A watery soft rot at nodes ✓
2. B black powder on leaf sheath ✓
3. C small galls on roots ✓
4. D reddening with white transverse patches ✓

The pathogen most associated with sugarcane red rot is

1. A Colletotrichum falcatum ✓
2. B Sclerospora graminicola ✓
3. C Puccinia sorghi ✓
4. D Plasmodiophora brassicae ✓

Whip smut of sugarcane produces a distinctive

1. A orange powder on lower leaves ✓
2. B black whip-like structure from the shoot apex ✓
3. C brown ring at the collar ✓
4. D white cottony growth on roots ✓

Citrus canker is classified as a

1. A viral disease ✓
2. B nematode disease ✓
3. C bacterial disease ✓
4. D physiological disorder ✓

Bacterial blight of cotton is generally favored by

1. A dry hot winds only ✓
2. B frost during boll opening ✓
3. C saline irrigation water ✓
4. D warm humid weather and rain splash ✓

Tikka disease of groundnut mainly affects the

1. A leaves ✓
2. B roots ✓
3. C flowers ✓
4. D seed embryo ✓

Roguing in crop disease management means

1. A spraying only after harvest ✓
2. B removing diseased or off-type plants from the field ✓
3. C mixing infected seed with healthy seed ✓
4. D increasing plant density to close gaps ✓

Bordeaux mixture is prepared mainly from

1. A sulfur and kerosene ✓
2. B zinc sulfate and gypsum ✓
3. C copper sulfate and lime ✓
4. D urea and potash ✓

Damping-off of nursery seedlings is usually intensified by

1. A wide spacing and dry soil ✓
2. B balanced potassium nutrition ✓
3. C deep summer ploughing ✓
4. D excess moisture and poor drainage ✓

Karnal bunt of wheat is primarily a disease of the

1. A grain ✓
2. B root ✓
3. C flag leaf ✓
4. D stem node ✓

Ergot disease replaces cereal grains with dark hard bodies known as

1. A uredospores ✓
2. B sclerotia ✓
3. C oospores ✓
4. D conidia ✓

Black scurf of potato is caused by

1. A Synchytrium endobioticum ✓
2. B Fusarium moniliforme ✓
3. C Rhizoctonia solani ✓
4. D Xanthomonas campestris ✓

The most effective long term approach for many viral crop diseases is

1. A high nitrogen application alone ✓
2. B deep irrigation after symptom appearance ✓
3. C late sowing in every season ✓
4. D resistant varieties combined with vector management ✓

A systemic fungicide commonly used as seed treatment against cereal smuts is

1. A carboxin ✓
2. B glyphosate ✓
3. C malathion ✓
4. D zinc phosphide ✓

Powdery mildew generally develops best under

1. A waterlogged soil and root anaerobiosis ✓
2. B mild temperatures with high relative humidity ✓
3. C strong frost with dry winds ✓
4. D deep standing water in fields ✓

Downy mildew sporulation is commonly promoted by

1. A hot dry winds and low humidity ✓
2. B saline soil and high pH only ✓
3. C cool humid conditions and leaf wetness ✓
4. D deficiency of phosphorus only ✓

Clubroot of cruciferous vegetables is caused by

1. A Alternaria brassicae ✓
2. B Sclerotinia sclerotiorum ✓
3. C Erysiphe cichoracearum ✓
4. D Plasmodiophora brassicae ✓

Bacterial wilt of tomato, potato and other solanaceous crops is caused by

1. A Ralstonia solanacearum ✓
2. B Pseudoperonospora cubensis ✓
3. C Tilletia indica ✓
4. D Ustilago tritici ✓

Early blight of tomato and potato is caused by

1. A Phytophthora infestans ✓
2. B Alternaria solani ✓
3. C Fusarium udum ✓
4. D Puccinia striiformis ✓

Fusarium wilt pathogens often persist in soil mainly as

1. A zoospores only ✓
2. B pollen grains ✓
3. C chlamydospores ✓
4. D bacterial endospores ✓

Root-knot nematode damage is commonly recognized by

1. A orange pustules on leaves ✓
2. B black sori in flowers ✓
3. C honeydew on stems ✓
4. D gall formation on roots ✓

A reliable first step to reduce seed-borne crop diseases is to use

1. A certified disease-free seed with suitable seed treatment ✓
2. B ungraded seed from infected fields ✓
3. C seed stored with high moisture ✓
4. D seed mixed across unknown sources ✓

The plant disease triangle consists of

1. A soil, fertilizer and irrigation only ✓
2. B susceptible host, virulent pathogen and favorable environment ✓
3. C seed, pesticide and machinery only ✓
4. D temperature, rainfall and wind only ✓

The latent period of a plant disease is the time between infection and

1. A sowing of seed ✓
2. B first irrigation ✓
3. C production of new infectious propagules ✓
4. D harvesting of crop ✓

Protectant fungicides give best results when applied

1. A after plants are completely dead ✓
2. B only during grain storage ✓
3. C only after roots decay ✓
4. D before infection occurs ✓

Anthracnose diseases commonly produce

1. A sunken necrotic lesions ✓
2. B root nodules with nitrogen fixation ✓
3. C silvering due to mites ✓
4. D green mosaic without necrosis ✓

Aflatoxin contamination in groundnut and maize is mainly associated with

1. A Rhizobium leguminosarum ✓
2. B Aspergillus flavus ✓
3. C Azotobacter chroococcum ✓
4. D Bacillus thuringiensis ✓

Common scab of potato is favored by

1. A strongly acidic waterlogged soil ✓
2. B continuous flooding at tuberization ✓
3. C neutral to alkaline dry soil ✓
4. D complete absence of oxygen in soil ✓

Wheat seed gall nematode disease is commonly called

1. A red rot ✓
2. B white rust ✓
3. C khaira disease ✓
4. D ear cockle ✓

Mosaic symptoms in crop plants most commonly suggest infection by a

1. A virus ✓
2. B nematode only ✓
3. C rodent pest ✓
4. D nutrient salt crystal ✓

Plant quarantine primarily aims to

1. A increase pesticide sales in local markets ✓
2. B prevent entry and spread of exotic pests and pathogens ✓
3. C replace seed certification systems ✓
4. D raise soil organic matter directly ✓

Hot water treatment of seed is used to

1. A increase seed moisture for storage ✓
2. B convert hybrid seed into pure lines ✓
3. C eliminate certain seed-borne pathogens under controlled temperature ✓
4. D replace all field sanitation measures ✓

Collar rot and stem rot caused by soil-borne fungi are often encouraged by

1. A complete absence of organic residues ✓
2. B very wide crop rotation only ✓
3. C dry sterile seedbeds only ✓
4. D warm moist soil and infected plant debris ✓

A physiological race of a pathogen is best described as a strain differing in

1. A virulence on host differential varieties ✓
2. B shape of farm machinery required ✓
3. C amount of fertilizer needed by crop ✓
4. D method of grain threshing ✓

Horizontal resistance in crops is generally

1. A controlled by one major gene only ✓
2. B polygenic, partial and relatively durable ✓
3. C effective against insects only ✓
4. D a symptom of nutrient toxicity ✓

The classic alternate host of wheat stem rust is

1. A berseem ✓
2. B sunflower ✓
3. C barberry ✓
4. D sorghum ✓

Smut fungi commonly produce dark masses of

1. A ascospores only ✓
2. B zoospores only ✓
3. C conidiophores only ✓
4. D teliospores ✓

Angular leaf spots with bacterial ooze most strongly indicate a

1. A bacterial disease ✓
2. B viral deficiency complex ✓
3. C nematode cyst disease ✓
4. D storage insect injury ✓

Soil solarization helps manage soil-borne diseases by

1. A cooling soil below freezing point ✓
2. B trapping solar heat under transparent polyethylene ✓
3. C adding nitrogen directly from sunlight ✓
4. D blocking all oxygen permanently ✓

Crop rotation is least effective against pathogens that

1. A survive only on one short-season crop ✓
2. B lack any resting structures ✓
3. C have wide host range and long-lived survival structures ✓
4. D die immediately after harvest ✓

Late blight management in potato relies heavily on

1. A late harvesting without field scouting ✓
2. B excess nitrogen and overhead irrigation ✓
3. C use of visibly infected seed tubers ✓
4. D sanitation, resistant varieties and timely fungicide sprays ✓

Stripe rust of wheat is favored mainly by

1. A cool humid weather ✓
2. B very hot dry winds ✓
3. C saline irrigation alone ✓
4. D deep flooding for weeks ✓

Integrated disease management means

1. A using one pesticide repeatedly every week ✓
2. B combining compatible methods based on disease ecology ✓
3. C ignoring host resistance in all crops ✓
4. D controlling only weeds after harvest ✓