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Biology H > Weeds > Flashcards

Weeds Flashcards

1
Q

What is crop productivity reduced by?

A

weeds
pests
diseases

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2
Q

How can we ensure the greatest yield of crop?

A

Tightly control, weeds pests and fungal infections

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3
Q

Why are weeds bad?

A

They can compete with crop plants for resources and reduce yield

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4
Q

What are the two main groups of weeds?

A

Perennial weeds

annual weeds

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5
Q

Properties of perennial weeds

A

-Live for several years
-become dormant in winter-time
-grow again in the spring

-storage organs
-vegetative reproduction

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6
Q

Properties of annuals weeds

A

Complete there entire life-cycle in one year

-high seed output
-short life cycle
-rapid growth
-long-term seed viability

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7
Q

Are most pests of plants invertebrate or vertebrate? +examples

A

invertebrate

such as insects, nematode worms and molluscs

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8
Q

Effects of invertebrate pests

A

-they DESTROY LEAVES

-this reduces the plant’s ability to carry out PHOTOSYNTHESIS and therefore their ability to PRODUCE SUGAR

-this causes a reduction in VIGOUR and YIELD OF CROP

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9
Q

What are plant diseases caused by? and what are the 3 types?

what are they often carried by?

A

pathogens

-fungi
-bacteria
-viruses

These diseases are often carried by invertebrate vectors (carriers

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10
Q

What are the 2 ways in which weeds, pests and disease controlled?

A

by cultural means
by chemical means

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11
Q

cultural methods of crop protection

A

1-ploughing
2-weeding
3-crop rotation

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12
Q

Chemical means of crop protection

A

pesticides

including:
-herbicides to kill weeds
-fungicides to control fungal disease
-insecticides to kill pests
-molluscicides to kill mollusc pests
-nematicides to kill nematode worms

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13
Q

What are pesticides?

A

chemicals which are applied to crop plants to protect them from damage

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14
Q

What 2 types of pesticides are there?

A

systemic and selective

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15
Q

What are systemic pesticides?

A

systemic insecticides, molluscicides and nematicides spread through the vascular system and kill pests feeding on plants

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16
Q

what are systemic herbicides

A

-applied to **kill weeds*
-They are absorbed into the plant’s transport system and quickly spread through the vascular system of the plant
-This has a lethal effect on the leaves and the roots of the plant so avoids regrowth of the weeds

17
Q

What are selective herbicides?

A

-they mimic the action if plant regrowth hormones
-they work by being absorbed through the leaves
-this speeds up the metabolism of plants to the extent that they use up their food reserves and die
-selective herbicides have a greater effect on certain plant species (broad leaved weeds)

18
Q

What do farmer’s often apply fungicides based off of?

A

disease forecasts
This is a preventative method
and is more effective than treating crops which are already diseased

19
Q

What issues can the use of pesticides lead to?

A

-Toxicity to non-target species

-persistence in the environment , bioaccumulation or biomagnification in food chains

-producing resistant populations of pests

20
Q

What is bioaccumulation?

A

A build-up of chemicals in an organism

21
Q

What is biomagnification?

A

An increase in the concentration of a chemical moving between tropic levels

22
Q

What is biological control?

A

The control of a pest population through the introduction of one of its natural ‘enemies)

23
Q

What types of biological controls are there?

A

A predator
A parasite
A pathogen of the pest

24
Q

What is the main advantage of using a biological control?

A

No chemicals are used which may persist in the environment

25
Q

Problems with biological control

A

The control organism may become an invasive species, parasite, prey or be a pathogen of another species

26
Q

What is Integrated pest management (IPM)

A

IPM uses a combination of chemical, biological and cultural control to improve yield

27
Q

What is the main aim of IPM

A

to reduce chemical use and only use chemicals which do not persist and reduce pests to levels which allow biological control methods to take over

Biology H (11 decks)

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