Weed Control Methods in Agriculture

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Questions and Answers

What is one way in which weeds damage agricultural plants?

  • Providing shade and helping with photosynthesis
  • Enhancing crop growth and yield
  • Serving as a protective barrier against pests
  • Competing with crops for essential nutrients (correct)

How do weeds affect the process of photosynthesis in crop plants?

  • By shading crop plants and reducing available sunlight (correct)
  • By promoting the growth of beneficial microorganisms
  • By providing additional sunlight
  • By increasing the efficiency of photosynthesis

What is a potential consequence of weeds harboring insects and disease organisms?

  • Enhancing soil fertility
  • Increasing crop yield through natural pollination
  • Reducing the need for pesticides on crops
  • Spreading pests and diseases to the crops (correct)

How do weed seeds impact the value of soybeans?

<p>Decrease the value by causing impurities (D)</p> Signup and view all the answers

Which method is used to control weeds by targeting specific weed species without affecting crop plants?

<p>Genetic modification of crops (A)</p> Signup and view all the answers

What is a challenge associated with controlling weeds among crop plants?

<p>Managing pests attracted by weed species (C)</p> Signup and view all the answers

What is one disadvantage of picking cotton among weeds?

<p>Reduced profit due to trash removal (D)</p> Signup and view all the answers

Why was the use of mechanical means for battling weeds considered expensive?

<p>Machinery, fuel, and labor costs were high (A)</p> Signup and view all the answers

What is the purpose of selective herbicides?

<p>To not harm the crop while killing certain weeds (A)</p> Signup and view all the answers

What distinguishes nonselective herbicides from selective herbicides?

<p>Selective herbicides kill certain types of plants (A)</p> Signup and view all the answers

Why are chemical herbicides preferred over mechanical means for controlling weeds?

<p>They are more cost-effective (D)</p> Signup and view all the answers

What challenge is posed by the wide variety of weeds that infect crops?

<p>Increase in production costs (B)</p> Signup and view all the answers

What is a benefit of Bt-mediated insect resistance compared to spraying pesticides?

<p>All plant parts are protected (A)</p> Signup and view all the answers

What is a major problem faced by producers using chemical pesticides to control insects that attack plant roots?

<p>Chemicals may not reach the roots of the plants (C)</p> Signup and view all the answers

Why can spraying pesticides over thick foliage be problematic?

<p>The foliage prevents the chemicals from reaching all leaves (C)</p> Signup and view all the answers

What is a challenge associated with systemic pesticides in food crops?

<p>They can leave residues in the edible parts of plants (C)</p> Signup and view all the answers

What is one problem with plants treated with systemic pesticides?

<p>They may take up insufficient insecticide to be effective (A)</p> Signup and view all the answers

Why can topical application of chemicals be ineffective if an insect has burrowed into the stem of a plant?

<p>Chemicals cannot reach the burrowed insect (C)</p> Signup and view all the answers

Flashcards

Weed Damage to Plants

Weeds compete with crops, depriving them of essential nutrients needed for growth and yield.

Weeds and Photosynthesis

Weeds can shade crop plants, reducing the amount of sunlight available for photosynthesis.

Weeds as Disease Vectors

Weeds may harbor insects and disease organisms, facilitating the spread of pests and diseases.

Weed Seeds Impact

Weed seeds mixed with soybeans decrease the grain's value due to impurities.

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Genetic Weed Control

Genetic modification allows crops to resist specific herbicides, targeting weeds while leaving crops unharmed.

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Pests Attracted by Weeds

Weeds attract harmful pests that can then infest and damage crop plants.

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Picking Cotton in Weeds

Picking cotton among weeds makes trash removal difficult, reducing profitability.

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High Cost of Weed Machinery

Mechanical weed control involves high costs for machinery, fuel, and labor.

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Selective Herbicides Defined

Selective herbicides are designed to kill specific weeds without harming the intended crop.

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Nonselective vs Selective

Nonselective herbicides kill all types of plants, while selective herbicides target only certain types.

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Cost-Effectiveness of Herbicides

Chemical herbicides are more cost-effective compared to the expenses of mechanical means.

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Variety of Weeds

A wide variety of weeds increases production costs.

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Bt Insect Resistance

Bt-mediated insect resistance protects all plant parts from insects, reducing the need for pesticides.

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Pesticide Reach

Chemicals may not effectively reach the roots of plants, limiting their impact on root-attacking insects.

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Foliage Blocking Chemicals

Thick foliage can prevent chemicals from reaching all the leaves.

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Systemic Pesticide Residue

Systemic pesticides can leave harmful residues in the edible portions of food crops.

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Insufficient Insecticide Uptake

Plants treated with systemic pesticides may not absorb enough insecticide to be fully effective.

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Burrowing Insects

Topical application of chemicals is ineffective when insects have burrowed into the stem.

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Study Notes

Weeds in Agriculture

  • Cotton picked with weeds has reduced profit due to the need to remove trash from the lint
  • Mechanical means of controlling weeds, such as hoeing and plowing, are expensive and can lead to soil erosion
  • Chemical herbicides were developed to kill weeds, with non-selective herbicides killing all plants and selective herbicides killing specific types of plants

Types of Herbicides

  • Non-selective herbicides, also known as knockdown herbicides, kill all plants they are applied to
  • Selective herbicides kill certain types of plants, such as grasses or broadleaf plants

Problems with Herbicides

  • Application of pesticides can be expensive due to machinery, fuel, and labor costs
  • There is a wide variety of weeds that infect crops, making it difficult to control them
  • Selective herbicides may not be effective against all types of weeds

Effects of Weeds on Agriculture

  • Weeds compete with crops for essential growth materials, such as soil nutrients
  • Weeds can shade crops, reducing sunlight and slowing crop growth
  • Weeds can harbor insects and disease organisms that can spread to crops
  • Weeds can cause impurities in agricultural products, reducing their value

Benefits of Biotech Crops

  • Biotech crops can provide a financial benefit to producers by reducing the need for pesticides
  • Bt-mediated insect resistance protects all plant parts, unlike chemical pesticides which may not reach all areas of the plant

Limitations of Chemical Pesticides

  • Chemical pesticides may not reach all areas of the plant, such as the roots or stems
  • Systemic pesticides can be problematic due to the potential for residues in edible plant parts and the need for long withdrawal periods before harvest.

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