Comprehensive Guide to Biotic and Abiotic Stress in Crops

What is abiotic stress?

Stress caused by environmental factors such as heat, light, cold, relative humidity, and rain.

What is biotic stress?

Stress caused by living organisms such as insects, pests, weeds, pathogens, and animals.

What does necrosis refer to in plants?

The death of plant tissue.

What is chlorosis?

The yellowing of leaf tissue due to a lack of chlorophyll.

How is a plant disease defined?

Any abnormal condition that alters the appearance or function of a plant, affecting its physiological processes.

What is the difference between disease and injury in plants?

Disease is a process or change that occurs over time, while injury occurs instantly.

What is a symptom in the context of plant diseases?

A plant's visible response to a pathogen.

What are plant pathogens?

Living organisms that cause infectious plant diseases by attacking and obtaining nutrition from the plants they infect.

Name four common types of plant pathogens.

Fungi, bacteria, viruses, and nematodes.

What is the role of a host in plant pathology?

The plant invaded by the pathogen and serving as its food source.

What is the disease triangle?

A model that identifies three factors needed to produce a disease: the pathogen, the host, and the environment.

What are fungi?

Organisms that lack chlorophyll and are composed of delicate, threadlike filaments called hyphae.

How do fungi typically enter plants?

Through natural openings, injuries, or direct penetration.

What are some symptoms of fungal diseases?

Leaf spots, blights, wilts, rots, and cankers.

What is damping off?

A type of fungal disease that affects seedlings, causing them to collapse.

What are bacterial diseases characterized by?

Symptoms such as leaf spots, wilts, stunting, and yellowing.

What is a common method of managing bacterial diseases?

Using resistant varieties and practicing good sanitation.

How are viral diseases transmitted in plants?

Many viral diseases are transmitted by insects known as vectors.

What are nematodes?

Microscopic roundworms that feed on plants using a structure called a stylet.

What is the role of mycoplasmas in plant diseases?

Microorganisms with no cell wall that can cause diseases like Aster yellows.

What environmental factors are critical for disease development?

A favorable environment is necessary; even susceptible plants will not develop disease without it.

What is the significance of soil in the survival of pathogens?

Soil can harbor resistant structures of pathogens, allowing them to survive until the next growing season.

What is the impact of crop stubbles on pathogens?

They can serve as hiding places for pathogens, facilitating their survival for the next season.

What is the role of water in the dissemination of pathogens?

Water can carry or splash spores, aiding in the spread of fungal diseases.

What factors determine the rate of disease development in plants?

Temperature, humidity, and moisture.

What is host resistance in plant disease management?

The ability of a host (plant) to restrict or prevent disease symptoms due to resistance genes.

What is general resistance in plants?

Horizontal resistance that allows resistant plants to stay green and healthy while slowing down disease development.

What is specific resistance in plants?

Vertical resistance that is race-specific and works only against one or few races of pathogens.

What are some cultural practices for managing plant diseases?

Using disease-free seeds, adjusting planting time, tillage, and crop rotation.

Why is the destruction of volunteer plants important in disease management?

It prevents the harboring of plant pathogens from weeds and leftover plants.

How can controlling insect vectors help in plant disease management?

It helps manage vector-borne virus diseases.

What types of chemical management are used in plant disease control?

Seed treatment with pesticides, fungicides, nematicides, and bactericides.

What are the economic impacts of weeds on agriculture?

Weeds cause economic loss by competing for resources and increasing production costs.

How are weeds classified?

By level of invasiveness, environment, life cycles, and taxonomy.

What defines noxious weeds?

Weeds defined by the Federal Noxious Weed Act that can injure crops and are usually of foreign origin.

What are invasive plants?

Generally non-native plants that establish in natural areas and displace native vegetation.

What is an example of a particularly destructive invasive plant?

Kudzu.

What distinguishes terrestrial weeds from aquatic weeds?

Terrestrial weeds live on land, while aquatic weeds live in water.

What are the life cycle classifications of weeds?

Annuals, biennials, and perennials.

What characterizes annual weeds?

They complete their life cycle in one year.

What is the life cycle of biennial weeds?

They germinate in the first year and flower and die in the second year.

What defines perennial weeds?

Weeds that live for more than two years.

What are the differences between grasses and broadleaves?

Grasses are monocots with parallel venation; broadleaves are dicots with reticulate venation.

What is allelopathy in relation to weeds?

The release of chemicals by plants that inhibit the growth of other plants.

What are parasitic weeds?

Weeds that rely on other plants for nutrients and can harm them.

What health issues can plants cause?

Damage through physical contact, such as with poison ivy and giant ragweed.

What happens to crop yield as weed density increases?

Crop yield drops as weed density increases.

What causes hay fever problems?

Windborne pollen, particularly from ragweed.

What is milk sickness and which plant is associated with it?

Milk sickness is caused by the snakeroot plant.

What are the unique traits of some weeds?

Seed production, seed dormancy, seed dispersal, vegetative reproduction, and weed biotypes.

How do most weeds reproduce?

Most weeds produce a large number of small seeds.

What is seed dormancy?

The ability of seeds to remain viable in soil for long periods until proper conditions for germination are met.

What is a seed bank?

The total dormant and nondormant seed accumulated in the soil.

How are weed seeds dispersed?

By water, wind, animals, and humans.

What is vegetative reproduction in weeds?

Asexual reproductive strategies without the use of seeds, such as rhizomes and stolons.

What are weed biotypes?

Weeds that develop special traits, such as herbicide resistance, to adapt to their environment.

What are some cultural practices for weed management?

Crop rotation, plant population management, cover crops, and using weed-free seed.

What is biological weed control?

The use of biological organisms, such as diseases or insects, to reduce or eliminate weed populations.

What is the primary method of weed control?

Herbicides.

What are the advantages of using herbicides?

Reduced cost, greater flexibility, effectiveness, and persistence.

What is herbicide resistance?

The tolerance of herbicides by weed species that were once susceptible.

What is integrated pest management (IPM)?

A strategy that integrates various management approaches to keep pest populations low in a cost-effective and environmentally friendly manner.

What are the stages of insect metamorphosis?

Egg, nymphs, and adult for incomplete metamorphosis; egg, larvae, pupae, and adult for complete metamorphosis.

What are common insect pests mentioned?

Aphids, potato leafhopper, weevils, Colorado potato beetle, corn earworm, and European corn borer.

What is the economic threshold (ET) in pest management?

The pest density at which management action should be taken to prevent reaching the economic injury level (EIL).

What is the economic injury level (EIL)?

The lowest pest population density that will cause economic damage, where yield losses equal insect management costs.

What is host plant resistance?

The use of insect pest-resistant crop varieties to minimize pest survival.

What is the role of sanitation in pest management?

Controlling weeds or volunteer plants to reduce refuge sites for insects.

What is biological control in crop insect pests?

The use of natural enemies, such as predators and parasitoids, to control insect pests.

What are broad-spectrum insecticides?

Insecticides that are toxic to non-target beneficial insects and have long residual effects.

What are reduced-risk insecticides?

Insecticides that are more selective and less destructive, preserving natural enemies and pollinators.

What is the purpose of classifying field crops?

To get acquainted with the crop, avoid confusion in identification, understand growth habits, climatic requirements, and economic uses.

What are cereal crops also known as?

Grain crops

Name two examples of cereal crops.

Rice and corn

Which family do legume crops belong to?

Leguminosae (Fabaceae) family

Give two examples of legume crops.

Chickpea and cowpea

What are fiber crops grown for?

Their fiber, which is used for making clothes, textiles, rugs, and ropes.

Name two examples of fiber crops.

Cotton and flax

What are forage crops used for?

They are grazed by animals or used to make fodder.

Give two examples of forage crops.

Alfalfa and clover

What is the primary purpose of oilseed crops?

They are grown for oil.

Name two examples of oilseed crops.

Sunflower and rapeseed

What are root crops grown for?

Their enlarged roots.

Give two examples of root crops.

Carrot and sweet potato

What distinguishes biennial crops from annual crops?

Biennial crops require two seasons to complete their life cycle.

What is binomial nomenclature?

A system that uses the last two categories of scientific names to name an organism.

What is the scientific name for wheat?

Triticum aestivum

What are the two types of cotyledons in plants?

Monocotyledons (one cotyledon) and dicotyledons (two cotyledons).

What is the effect of climate on crop production?

Climate influences the suitability of a crop to a region and affects yield potential.

How does latitude affect growing seasons?

Growing seasons vary from over 300 days in southern latitudes to only 70 days in some northern latitudes.

What are temperate plants?

Plants from regions of seasonal temperature changes that prefer cold weather.

Name an example of a tropical plant.

Corn

What is the significance of cardinal temperature points?

They define the minimum, optimum, and maximum temperature limits for plant growth.

What temperature range is considered optimum for wheat?

25°C

What are the effects of extreme low temperatures on plants?

They can affect cell structure.

What happens to enzyme systems in extreme high temperatures?

They can denature, leading to cell degradation and death.

What is the effect of high temperature on photosynthesis?

It reduces the amount of photosynthetic pigment and activity of the rubisco enzyme, and closes stomata, leading to reduced CO2 intake.

How does high temperature affect plant growth?

It leads to reduced germination, abnormal seedlings, poor seedling vigor, reduced nutrient absorption, loss of cell water content, and stunted growth.

What are the effects of high temperature on plant reproductive parts?

Impaired pollen germination, reduced pollen viability, reduced flower bud production, increased flower abortion, and impaired fruit set.

What morphological changes occur due to heat stress in plants?

Leaf scorching, sunburn, and stem scorches.