3.3) Crop Protection

Question 1

• What do weeds do and what are the properties of perennial and annual weeds?

Answer 1

• Weeds compete with crop plants, while other pests and diseases damage crop plants,
  ➞ all of which reduce productivity

1. PERENNIAL WEEDS ♾️
   ➞ type of weeds that continue to grow every season
   * storage organs (plant has food in all environmental conditions)
   * vegetative reproduction (perenneial weeds can reproduce using other methods in additon to seeds - sexual reproduction)
2. ANNUAL WEEDS 🗓️
   ➞ type of weed which completes its life cycle in one growing season or year
   * rapid growth
   * short life cycle
   * high seed output
   * long-term seed viability

Question 2

• What organisms can affect plant crops?

Answer 2

• Pests - Invertabrate animals:
  ➞ INSECTS (e.g. aphids)
  ➞ NEMATODES (e.g. parasitic roundworms)
  ➞ MOLLUSCS (e.g. slugs and snails)

Question 3

• How are plant diseases caught?

Answer 3

• Plant diseases can be caused by:
  ➞ FUNGI 🍄
  ➞ BACTERIA 🧫
  ➞ VIRUSES 🦠

Question 4

• What are some cultural control methods?

Answer 4

1. PLOUGHING
   ➞ buries perennial weeds so they die and decompose
2. WEEDING
   ➞ weeds removed early in the life of the crop allows the crop to become stronger
3. CROP ROTATION
   ➞ a series of different crops are grown on the same piece of land over time (the current crop will not have the same pests as the next crop)

Question 5

• What are some chemical control methods?

Answer 5

• Pesticides, which include:
  ➞ HERBICIDES (kill weeds) 🌿
  ➞ FUNGICIDES (control fungal diseases) 🍄
  ➞ INSECTICIDES (kill insect pests) 🪲
  ➞ MOLLUSCICIDES (kill mollusc pests) 🐌
  ➞ NEMATICIDES (kill nematode pests) 🪱

Question 6

• What are the advantages of selective or systemic pesticides?

Answer 6

• SELECTIVE:
  ➞ herbicides have a greater effect on certain plant species (broad leaved weeds)
  ↳ Crop plants absorb little of the chemical.
  ➜ Selective herbicides are biodegradable and do not cause harm to the soil.
• SYSTEMIC:
  ➞ herbicides spreads through the vascular system of plants and prevents regrowth
  ↳ other systemic pesticides (insecticides, molluscicides and nematicides) spread through the vascular system of plants and kill pests feeding on plants.

Question 7

• Describe problems with pesticides in terms of bioaccumulation and biomagnification.

Answer 7

• Some pesticides used in crop production have found to be toxic to non-target species (e.g. animals)
• There are examples of chemicals (such as DDT) that persist in the environment and accumulate over time.
  ➞ This is called bioaccumulation and involves the build up of chemicals in an organism.
• An increase in the concentration of a chemical (such as DDT) moving between the trophic levels of a food chain is known as biomagnification.
  ➞ This may lead to poisoning if animals further along the food chain, or resistant pest populations.

Question 8

• What is a biological control and can you explain the risks with biological control?

Answer 8

• ‘Biological control’
  ➞ reduces the pest population by using a natural parasite, predator or pathogen.
• The risks with a biological control
  ➞ include the control organism becoming an invasive species, or it becoming a parasite, predator or pathogen of another species.
• Invasive species can spread rapidly and/or eliminate native species

Question 9

• Describe ‘integrated pest managment’

Answer 9

• ‘Integrated pest management’
  ➞ is the combination of cultural, chemical and biological control.