Crop Diseases and Maize Streak Virus

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Questions and Answers

What are the two main categories of factors that cause plant diseases?

Abiotic and biotic factors.

List two harmful effects of crop diseases on plant yields.

Reduced yields and complete crop loss.

Which pathogen is responsible for maize streak virus, and how is it transmitted?

A virus, transmitted by sap-sucking leafhoppers.

What visual symptoms indicate a plant infected with maize streak virus?

Leaves turn light green with yellow stripes parallel to the veins. Signup and view all the answers

Identify one example of a bacterial disease and its affected plant.

Bacterial wilt of tomatoes. Signup and view all the answers

What is a common outcome for plants that experience stunted growth due to disease?

They do not reach their full size. Signup and view all the answers

Name a fungal disease that can affect seedlings.

Damping-off of seedlings. Signup and view all the answers

How does the maize streak virus affect the cob's quality during harvest?

Cobs are small and partially filled. Signup and view all the answers

What are two cultural control methods to manage maize streak virus?

Use resistant maize varieties and remove and burn infected plants. Signup and view all the answers

How does maize smut infect maize plants?

Fungal spores in the soil spread to young maize plants through wind and water, entering via cuts or wounds. Signup and view all the answers

What visible symptoms indicate a maize smut infection?

Large blackish lumps appear on stems, leaves, and cobs, releasing black spores. Signup and view all the answers

Identify two methods to control bacterial wilt in tomato plants.

Use certified seeds and practice crop rotation. Signup and view all the answers

What environmental factors can lead to bacterial wilt in tomatoes?

Soil-borne pathogens and contaminated irrigation water can facilitate the spread of bacterial wilt. Signup and view all the answers

What is the role of antibiotics in managing bacterial wilt of tomatoes?

Antibiotics are used to spray infected plants to combat the bacterial infection. Signup and view all the answers

How can early planting help control maize streak virus?

Early planting can help maize plants establish before the peak leafhopper populations emerge. Signup and view all the answers

What practice is recommended to help prevent maize smut infections when cultivating?

Avoid injury to the roots, stalks, and leaves during cultivation and fertilization. Signup and view all the answers

Study Notes

Crop Diseases

Plant disease is an abnormal condition in plants, caused by internal disorders (nutrition, stress) or infections (pathogens). Alternatively, it's deterioration and damage from biotic (living) or abiotic (non-living) factors.
Effects of diseases on crops: Reduced yields (fewer fruits, grains, vegetables), crop losses (complete loss possible), stunted growth (disease prevents full size), and discoloration of leaves/stems (leading to poor growth).
Classification of crop diseases: Categorized by causative agent:
- Bacteria: Examples include bacterial wilt of tomatoes, potatoes, cotton and more.
- Fungi: Examples include damping-off, downy mildew, smut, powdery mildew, and leaf spots.
- Viruses: Examples include maize streak virus, cowpea aphid-borne mosaic virus, cassava mosaic virus, and groundnut rosette virus.

Maize Streak Virus

Pathogen: Virus
Mode of infection: Transmitted by sap-sucking leafhoppers that acquire the virus from infected plants and then spread it to healthy plants.
Harmful effects: Yellow-green stripes on leaves, reduced photosynthetic area impacting plant growth and yield, smaller and less filled cobs. Inflorescence can become sterile reducing crop output.
Control methods:
- Use resistant maize varieties
- Remove and destroy infected plants
- Early planting
- Spray leafhoppers with dimethoate to kill them

Maize Smut

Pathogen: Fungus
Mode of infection: Fungal spores remain in the soil for years, spreading through wind, dust, rain and plant wounds to young maize plants.
Harmful effects: Large dark lumps on stems, leaves, and cobs; these lumps release spores that infect other plants; spores can also cover the entire grain, leading to complete grain loss.
Control methods:
- Avoid injury to plant parts (roots, stalks, leaves) during cultivation, spraying, and fertilization.
- Remove and destroy infected plants
- Use certified seed stock that is not affected by the disease
- Practice crop rotation

Bacterial Wilt of Tomatoes

Pathogen: Bacteria
Mode of infection: Soil-borne pathogen that enters through root wounds. Can spread through water or contaminated plant materials.
Harmful effects: Blocks water transport to stems thus leading to wilting and affecting plant structure.
Control methods:
- Use certified seeds and seedlings
- Avoid contaminated land and practice crop rotation
- Use appropriate planting procedures and preventative measures

Common Weeds of Botswana

Examples given include black jack, Mexican poppy, thorn apple, couch grass.

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Description

Test your knowledge on crop diseases, specifically focusing on the maize streak virus. Learn about the effects of diseases on yields, classifications by causative agents, and gain insight into pathogens like bacteria, fungi, and viruses that affect plants. This quiz will enhance your understanding of plant health and agricultural challenges.