Agricultural Science JAMB

Crop Diseases

Gbogbo ọrọ náà

Welcome to the course material on Crop Diseases!

Understanding crop diseases is crucial for agricultural practitioners as these diseases can lead to significant yield losses if not properly managed. This topic delves into the various types of diseases that can affect crops, including those caused by fungi, bacteria, nematodes, and viruses. By the end of this course, you will be able to distinguish between common store and field disease-causing organisms and relate each control method to its side effects.

Each category of disease-causing organisms has distinct characteristics and modes of spread. Fungi, for instance, are responsible for diseases like powdery mildew and rust, which can manifest as white or orange powdery growth on plant surfaces. Bacteria cause diseases such as bacterial blight and cankers, leading to wilting and lesions on plants. Nematodes are microscopic worms that attack plant roots, causing stunted growth and yield decline. Viruses, on the other hand, result in mosaic patterns and mottling on leaves.

The damage caused by these diseases can be devastating if left unchecked. This course will explore the nature of the damage inflicted by each type of pathogen and the symptoms that plants exhibit when infected. By learning about the methods of transmission, you will gain insights into how these diseases spread within crops and between fields.

When it comes to controlling crop diseases, various methods can be employed, each with its associated side effects. These control measures may include cultural practices, chemical treatments, and biological control agents. However, it is essential to be aware of the potential side effects of these methods, such as pollution, poisoning, and disruption of the ecosystem.

Throughout this course, you will also investigate the relationship between disease-causing organisms and their corresponding control methods. By applying appropriate control measures, you will not only protect crops from disease but also mitigate the negative impacts of these interventions on the environment.

By the end of this comprehensive course material, you will have a deep understanding of crop diseases, their causative agents, symptoms, transmission methods, and control strategies. This knowledge will equip you with the skills necessary to identify, manage, and prevent crop diseases effectively in agricultural settings.

Ebumnobi

Distinguish Between Common Store And Field Disease – Causing Organisms
Relate Each Control Method To Its Side Effect

Akọmọ Ojú-ẹkọ

Crop diseases are a significant concern in agriculture as they can lead to substantial losses in yield and quality. They are typically caused by various organisms such as fungi, bacteria, viruses, and nematodes. Understanding crop diseases, their causes, and control methods is crucial for effective agricultural management.

Samun duk kayan koyo

Practice na ajụjụ ndị gara aga.

Tọle ọgbọ rẹ.

Ayẹwo Ẹkọ

Ekele diri gi maka imecha ihe karịrị na Crop Diseases. Ugbu a na ị na-enyochakwa isi echiche na echiche ndị dị mkpa, ọ bụ oge iji nwalee ihe ị ma. Ngwa a na-enye ụdị ajụjụ ọmụmụ dị iche iche emebere iji kwado nghọta gị wee nyere gị aka ịmata otú ị ghọtara ihe ndị a kụziri.

Ị ga-ahụ ngwakọta nke ụdị ajụjụ dị iche iche, gụnyere ajụjụ chọrọ ịhọrọ otu n’ime ọtụtụ azịza, ajụjụ chọrọ mkpirisi azịza, na ajụjụ ede ede. A na-arụpụta ajụjụ ọ bụla nke ọma iji nwalee akụkụ dị iche iche nke ihe ọmụma gị na nkà nke ịtụgharị uche.

Jiri akụkụ a nke nyocha ka ohere iji kụziere ihe ị matara banyere isiokwu ahụ ma chọpụta ebe ọ bụla ị nwere ike ịchọ ọmụmụ ihe ọzọ. Ekwela ka nsogbu ọ bụla ị na-eche ihu mee ka ị daa mba; kama, lee ha anya dị ka ohere maka ịzụlite onwe gị na imeziwanye.

Name a common crop disease caused by fungi and state its method of transmission. A. Rust
B. Bacterial wilt
C. Root knot
D. Mosaic virus
Answer: A. Rust
What is a common symptom of bacterial crop diseases? A. Yellowing of leaves
B. Root rot
C. Leaf spot
D. Wilting of plant
Answer: D. Wilting of plant
Which of the following is a control method for nematode-induced crop diseases? A. Crop rotation
B. Pruning
C. Mulching
D. Watering
Answer: A. Crop rotation
How can viruses be transmitted to crops? A. Through contaminated soil
B. Through air
C. Through overwatering
D. Through mechanical injury
Answer: D. Through mechanical injury
What is a possible side effect of chemical control methods for crop diseases? A. Soil erosion
B. Increased soil fertility
C. Improved water retention
D. Enhanced nutrient uptake
Answer: A. Soil erosion

Samun duk kayan koyo

Practice na ajụjụ ndị gara aga.

Tọle ọgbọ rẹ.

Samun duk kayan koyo

Practice na ajụjụ ndị gara aga.

Tọle ọgbọ rẹ.

Àwọn Ìwé Tó Dáa Láti Kà

Plant Pathology

Ìkọ̀wé-àbáojú: An Advanced Guide

Onkọwe atẹjade: Springer

Afọ: 2015

ISBN: 978-3319089736

Soil Microbiology, Ecology, and Biochemistry

Ìkọ̀wé-àbáojú: Fourth Edition

Onkọwe atẹjade: Academic Press

Afọ: 2015

ISBN: 978-0124159556

Introduction to Plant Pathology

Ìkọ̀wé-àbáojú: Fifth Edition

Onkọwe atẹjade: Wiley

Afọ: 2003

ISBN: 978-0471728925

Àwọn Ìbéèrè Tó Ti Kọjá

Nna, you dey wonder how past questions for this topic be? Here be some questions about Crop Diseases from previous years.

Agriculture 0600 | Paper 1 Mock 01 | Theory

Ajụjụ 1 Ripọtì

Season	Crop disease	Loss (US$)	Livestock disease	Loss (US$)
1	Maize smut	1 200	Tick-borne diseases	3 500
2	Maize smut	2 800	Foot-and-mouth disease	12 000
3	Maize smut	4 500	Mastitis	2 200

A mixed farmer grows maize and keeps cattle on 200 hectares. The table shows the diseases recorded on the farm over three seasons.

(a) Using the information in the table, state which type of disease (crop or livestock) caused the greatest total economic loss over the three seasons. [1]

(b) Suggest two reasons why the loss from maize smut increased between Season 1 and Season 3. [2]

(c) Describe the symptoms of maize smut that help a farmer identify infected plants in the field. [3]

(d) Explain how crop rotation could help reduce the incidence of maize smut on this farm. [3]

(e) The farmer also lost cattle to foot-and-mouth disease in Season 2.

(i) State two symptoms of foot-and-mouth disease in cattle. [2]

(ii) Explain why the government may impose movement restrictions on farms affected by foot-and-mouth disease. [2]

(iii) Suggest two actions the farmer should take immediately if foot-and-mouth disease is suspected in the herd. [2]

Azịza

(a) Livestock disease caused the greatest total economic loss over the three seasons [1].

	Crop disease loss (US$)	Livestock disease loss (US$)
Season 1	1 200	3 500
Season 2	2 800	12 000
Season 3	4 500	2 200
Total	8 500	17 700

Livestock disease losses ($17,700) were more than double the crop disease losses ($8,500).

(b) Two reasons why maize smut losses increased from Season 1 ($1,200) to Season 3 ($4,500) (any two for [2]):

The farmer may not have practised crop rotation, so smut spores accumulated in the soil year after year, increasing the inoculum level available to infect each successive crop [1].
Infected plant debris was not removed or destroyed after harvest, allowing spores to persist in the soil and on the surface, infecting the next season's crop at progressively higher rates [1].

Also acceptable: repeated planting of the same susceptible variety; weather conditions increasingly favourable for the fungus.

(c) Symptoms of maize smut for field identification (3 marks):

Large, swollen, grey or black galls (tumour-like growths) develop on the ears, tassels, stems or leaves of the maize plant [1].
The galls are initially covered by a silvery-white membrane. When this membrane ruptures, it releases masses of dark, powdery teliospores [1].
Affected ears are deformed and produce little or no grain, reducing yield from those plants to nearly zero [1].

(d) How crop rotation reduces maize smut incidence (3 marks):

Growing a non-host crop (e.g. a legume or root crop) in the season following maize breaks the disease cycle because the smut fungus cannot infect the alternative crop [1].
Without a susceptible host, the spore population in the soil declines over time through natural degradation and the activity of antagonistic soil microorganisms [1].
After two or three seasons of rotation, maize can be replanted with a significantly reduced risk of infection because the soil inoculum has been depleted [1].

(e)(i) Two symptoms of foot-and-mouth disease in cattle (any two for [2]):

Blisters (vesicles) on the tongue, gums, lips, dental pad and around the hooves, which burst to leave painful ulcers [1].
Excessive salivation and drooling, often with strings of saliva hanging from the mouth [1].

Also acceptable: lameness; reluctance to eat; fever; drop in milk yield.

(e)(ii) Why the government imposes movement restrictions (2 marks):

Foot-and-mouth disease is highly contagious and spreads rapidly through direct contact, airborne droplets and contaminated vehicles. Restricting animal movements prevents infected animals from being transported to markets or other farms [1].
Movement restrictions contain the outbreak geographically, protecting the wider national livestock industry and international trade status, since FMD is a notifiable disease with major economic consequences [1].

(e)(iii) Two immediate actions if FMD is suspected (any two for [2]):

Isolate the suspected animals from the rest of the herd immediately to limit direct contact spread [1].
Report the suspected case to the veterinary authorities, as FMD is a notifiable disease that requires official intervention [1].

Also acceptable: stop all livestock movements on and off the farm; disinfect boots, equipment and vehicles.

Akọwa Nkọwa

(a) Livestock disease caused the greatest total economic loss over the three seasons [1].

	Crop disease loss (US$)	Livestock disease loss (US$)
Season 1	1 200	3 500
Season 2	2 800	12 000
Season 3	4 500	2 200
Total	8 500	17 700

Livestock disease losses ($17,700) were more than double the crop disease losses ($8,500).

(b) Two reasons why maize smut losses increased from Season 1 ($1,200) to Season 3 ($4,500) (any two for [2]):

The farmer may not have practised crop rotation, so smut spores accumulated in the soil year after year, increasing the inoculum level available to infect each successive crop [1].
Infected plant debris was not removed or destroyed after harvest, allowing spores to persist in the soil and on the surface, infecting the next season's crop at progressively higher rates [1].

Also acceptable: repeated planting of the same susceptible variety; weather conditions increasingly favourable for the fungus.

(c) Symptoms of maize smut for field identification (3 marks):

Large, swollen, grey or black galls (tumour-like growths) develop on the ears, tassels, stems or leaves of the maize plant [1].
The galls are initially covered by a silvery-white membrane. When this membrane ruptures, it releases masses of dark, powdery teliospores [1].
Affected ears are deformed and produce little or no grain, reducing yield from those plants to nearly zero [1].

(d) How crop rotation reduces maize smut incidence (3 marks):

Growing a non-host crop (e.g. a legume or root crop) in the season following maize breaks the disease cycle because the smut fungus cannot infect the alternative crop [1].
Without a susceptible host, the spore population in the soil declines over time through natural degradation and the activity of antagonistic soil microorganisms [1].
After two or three seasons of rotation, maize can be replanted with a significantly reduced risk of infection because the soil inoculum has been depleted [1].

(e)(i) Two symptoms of foot-and-mouth disease in cattle (any two for [2]):

Blisters (vesicles) on the tongue, gums, lips, dental pad and around the hooves, which burst to leave painful ulcers [1].
Excessive salivation and drooling, often with strings of saliva hanging from the mouth [1].

Also acceptable: lameness; reluctance to eat; fever; drop in milk yield.

(e)(ii) Why the government imposes movement restrictions (2 marks):

Foot-and-mouth disease is highly contagious and spreads rapidly through direct contact, airborne droplets and contaminated vehicles. Restricting animal movements prevents infected animals from being transported to markets or other farms [1].
Movement restrictions contain the outbreak geographically, protecting the wider national livestock industry and international trade status, since FMD is a notifiable disease with major economic consequences [1].

(e)(iii) Two immediate actions if FMD is suspected (any two for [2]):

Isolate the suspected animals from the rest of the herd immediately to limit direct contact spread [1].
Report the suspected case to the veterinary authorities, as FMD is a notifiable disease that requires official intervention [1].

Also acceptable: stop all livestock movements on and off the farm; disinfect boots, equipment and vehicles.

Wo Idahun

Samun duk kayan koyo

Practice na ajụjụ ndị gara aga.

Tọle ọgbọ rẹ.

Crop Diseases

Gbogbo ọrọ náà

Ebumnobi

Akọmọ Ojú-ẹkọ

Yi rajista ka ci gaba

Ayẹwo Ẹkọ

Yi rajista ka ci gaba

Yi rajista ka ci gaba

Àwọn Ìwé Tó Dáa Láti Kà

Àwọn Ìbéèrè Tó Ti Kọjá

Yi rajista ka ci gaba