Weed Science Overview

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Questions and Answers

Which of the following species does not reproduce asexually?

Tridax prucumbens (correct)

Fimbristylis littoralis

Cynadon dactylon

Cyperus rotundus

What type of weed can grow vegetatively, produce seeds, and live for more than two years?

Annual weed

Dicot weed

Perennial weed (correct)

Biennial weed

What enables Cyperus rotundus to persist in its environment?

It produces asexually (correct)

It produces sexually

It is a broadleaf plant

Its seeds have a short viability period

Why is it difficult to identify weeds at the seedling stage?

Weeds cannot be easily seen due to their small size Signup and view all the answers

What type of weed is completely submerged in water?

Submergent Signup and view all the answers

What role do weeds play in controlling soil erosion?

They help in checking wind, water, and soil erosion. Signup and view all the answers

Which of the following weeds is recognized for its use as a trap crop for the Asian corn borer?

Spiny amaranth Signup and view all the answers

What is one economic importance of weeds?

They can serve as ornamental plants. Signup and view all the answers

How are biennial weeds characterized?

They germinate and form a rosette in the first year and complete their cycle in two years. Signup and view all the answers

Which of the following is NOT a benefit derived from weeds?

Harboring harmful viruses. Signup and view all the answers

What classification do weeds fall under if they last for more than two years?

Perennial Signup and view all the answers

Which of the following properties do some weeds possess that can help control nematodes?

Nematicidal properties. Signup and view all the answers

What is a common misconception about weeds?

They are only harmful to crops. Signup and view all the answers

What is the primary reason weeds are considered to be a problem in agro-ecosystems?

They compete with crops for essential growth materials. Signup and view all the answers

Which characteristic is commonly associated with serious weed problems?

They adapt quickly to changing environments. Signup and view all the answers

How are weeds defined in relation to humans?

Plants that are unwanted in a certain location and time. Signup and view all the answers

What role do weeds play in relation to crops and other pests?

They serve as alternate hosts for insects and diseases. Signup and view all the answers

Which statement best defines the origin of many weeds?

They largely originated from man-made environments. Signup and view all the answers

What is a misconception about weeds?

All unwanted plants can become major weed problems. Signup and view all the answers

Which of the following scenarios accurately portrays the adaptive nature of weeds?

Weeds can easily outcompete crops for resources. Signup and view all the answers

In what way do weeds affect the economic value of agricultural products?

They lower the overall yield of crops. Signup and view all the answers

Which of the following defines creeping perennials?

Plants that propagate by seeds and vegetative parts Signup and view all the answers

Which type of aquatic weed is characterized by having its roots attached to the soil, while the leaves remain above the water surface?

Emergent Signup and view all the answers

What is a distinguishing feature of sedges compared to grasses?

Triangular solid stem Signup and view all the answers

Which of the following is true about epiphytic weeds?

They require a host plant for support. Signup and view all the answers

What distinguishes the grasses from other plant families?

They have long leaf blades with parallel veins. Signup and view all the answers

Which of the following is an example of a submergent aquatic weed?

Hydrilla verticillata Signup and view all the answers

Which term refers to terrestrial weeds found specifically in rice fields?

Grassland Signup and view all the answers

What characteristic describes a ligule in grasses?

A membranous outgrowth at leaf junctions Signup and view all the answers

Which of the following is an example of a creeping weed?

Cynadon dactylon Signup and view all the answers

Which of these weed species is categorized as a broadleaf?

Monochoria vaginalis Signup and view all the answers

What is the primary characteristic of herbaceous weeds?

They can be easily controlled chemically. Signup and view all the answers

What does the term 'persistence' refer to in the context of weeds?

The ability of a weed to grow in disturbed environments. Signup and view all the answers

Which of the following weed types is classified as woody?

Lantana camara Signup and view all the answers

What is a common growth habit of weeds found among plantation crops?

Vines Signup and view all the answers

Which measurement indicates how well a weed can adapt to changes in its environment?

Adaptability Signup and view all the answers

Which of these weeds is typically considered herbaceous?

Cyperus rotundus Signup and view all the answers

Study Notes

Weed Science Defined

Weed science examines weed establishment, spread, impact, characteristics, identification, and control.
Weeds are plants that can be harmful to agricultural ecosystems.
Weeds have adapted to thrive in human-influenced environments.

Weed Characteristics

Weeds are often considered noxious due to their adaptability.
Weeds possess characteristics that promote persistence and competitiveness, often shared with crops.
Not all unwanted plants become major weed problems.

Relationship Between Weeds, Crops, and Other Pests

Weeds are pests, like insects and diseases, and negatively affect agriculture.
Weeds compete with crops for resources such as nutrients, water, sunlight, and space.
Weeds may lower the quality of crop products and serve as hosts for insects and diseases.
Weeds can be beneficial, providing soil erosion control and livestock feed.

Importance of Weeds

Weeds contribute organic matter and nutrients to the soil.
Weeds help prevent wind, water, and soil erosion.
Some weeds serve as animal fodder, leafy vegetables, and possess medicinal properties.
Weeds have economic importance and can be used ornamentally or for hedging.
Weeds can have nematicidal properties, controlling nematodes.

Weed Classification

By Life Cycle

Annuals complete their life cycle within a year or growing season.
- Examples include Phyllanthus niruri and Euphorbia hirta.
Biennials complete their life cycle over two years.
- An example is Wild carrot (Daucus carota subsp.maximus).
Perennials survive for more than two years and reproduce via seeds or vegetatively.
- Simple perennials reproduce only by seeds.
  - Examples include Chromolaena odorata and Sida acuta.
- Creeping perennials reproduce by seeds and through vegetative means like rhizomes, runners, stolons, tubers, and bulblets.
  - Examples include Centella asiatica and Commelina diffusa.

By Habitat

Terrestrial weeds live on land.
- Subcategories include rice field, garden, grassland, wasteland, forest, and field weeds.
Aquatic weeds live in water.
- Floating weeds grow on the water surface and aren't rooted in the soil.
  - Example: Eichhornia crassipes
- Emergent weeds have roots in the soil and leaves above the water surface.
  - Example: Monochoria vaginalis
- Submergent weeds have roots in the soil and are fully submerged.
  - Example: Hydrilla verticillata
Epiphytes need a host plant for support and lack roots.
- Example: Lichens, algae, ferns, orchids.

Morphology

Grasses belong to the Graminae family.
- Characteristics include cylindrical hollow stems with nodes and internodes, narrow leaves with parallel veins, and a ligule at the leaf sheath-leaf blade junction.
- Example: Eleusine indica (Goose grass)
Sedges belong to the Cyperaceae family.
- Characteristics include a triangular solid stem lacking nodes and internodes, long leaves with parallel veins, no ligule, fused leaf sheaths forming a tube around the stem, and angular or triangular stems.
- Example: Cyperus rotundus (Nut sedge)
Broadleaves belong to other families.
- Characteristics include expanded leaves with net veins in various sizes, shapes, and arrangements.
- Example: Ipomea triloba (Kamote-kamotehan)

Growth Habit

Creeping weeds have parts that spread along the ground.
- Example: Cynadon dactylon
Vines are common among plantation crops like banana and pineapple.
Shrubs are common in cattle ranches in the Philippines.
- Examples: Chromolaena odorata and Lantana camara
- Trees are considered weeds when they grow in unwanted areas.
Herbaceous weeds are soft-bodied and generally easier to control chemically.
- Example: Portulaca spp.
Woody weeds are hard to control due to their woody texture.
- Example: Lantana camara

Ten World's Worst Weeds

The text highlights 10 of the world's most problematic weeds.
Infographics can be used to illustrate weed characteristics, classification, and impact on agriculture.

Importance of Weed Identification

Early identification of weeds is essential for effective control.
Weed identification can be challenging at the seedling stage due to similarities among species.

Relationship of Weeds to Crop Production

Weeds are considered pests in most agricultural settings.
Weed presence can significantly disrupt crop production.

Classification of Aquatic Weeds

Emergent weeds have roots in the soil and leaves above the water surface.
Floating weeds live on the surface and aren't rooted.
Submergent weeds are completely submerged.
Terrestrial weeds are land-based.

Understanding Weed Control

Weed control methods need to be adapted based on the type of weed present.
Herbicides are often used for weed control but can have environmental consequences.
Mechanical control methods such as hand weeding and tillage are also used.

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Description

This quiz provides an overview of weed science, including the characteristics, impacts, and relationships between weeds and crops. Explore the adaptability of weeds and their role in agricultural ecosystems. Test your knowledge on the importance of weeds and their effects on crop production.