R2103 3.3 Describe the biology of pests

Question 1

Methods of feeding: Rabbits

Answer 1

• Grazing animal - relatively clean cuts
• Most feeding done dusk till dawn
• Bark gnawed from base of trunks - especially in snow/frost covered ground
• Can ring-bark trees and kill them

Question 2

Methods of feeding: cabbage white (large white) butterfly larvae

Answer 2

1. Holes are eaten in the outer leaves of brassicas and damage may be seen on the inner leaves of cabbages when heart is cut through
2. Has biting mouthparts

Question 3

NAME 2 PESTS THAT CAUSE DAMAGE BY BITING

Answer 3

1. rabbits
2. large cabbage white butterfly larvae
3. adult and larval forms of vine weevil
4. mice

Question 4

NAME 2 PESTS THAT CAUSE DAMAGE BY PIERCING

Answer 4

1. aphids
   
   2. two spotted spider mite
      3.whitefly

Question 5

Methods of feeding: Black bean aphid

Answer 5

1. Piercing and sucking mouthparts
2. Sucks sugery phloem liquid from leaves and flowers often leading to a sooty mold
3. Can transmit viruses

Question 6

Methods of feeding: peach potato aphid

Answer 6

1. Piercing / sucking with their feeding tubes and sucking the sap
2. Digestive juices injected into phloem may lead to distorted buds
3. Can infect the plant with a virus e.g. mosaic virus, leaf-roll virus
4. Excretes plant sugars as sticky honeydew when they feed - leading to black sticky molds

Question 7

Methods of feeding: two-spotted spider mite

Answer 7

1. Piercing / sucking mouthparts
2. Inject poisonous juices which cause localised death of leaf cells - results in fine mottling of leaf
3. Suck sap

Question 8

Methods of feeding: glasshouse whitefly

Answer 8

1. Sucking stylets which extract sugery phloem causing large amounts of honeydew and sooty molds on leaf surface

Question 9

Methods of feeding: vine weevil

Answer 9

1. Adults eat out notch like holes in leaves or round the edges of plants
2. Grubs cause most damage in autumn/winter when they feed on plant roots
3. Strong biting mouthparts which tear up leaf sections to chew

Question 10

Methods of feeding: Slugs

Answer 10

1. Slugs and snails break down plant tissue with their rasping ‘radula; covered by tiny recurved teeth
2. Plant tissues are rasped with a tongue-like radula
3. Acts like a nail file leaving irregular holes in seedlings, roots, bulbs, corms, tubers, leaves, buds and fruits

Question 11

Methods of feeding: Potato cyst eelworm

Answer 11

1. Feed by puncuring plant cells and feeding on their contents
2. Some will feed on root hairs
3. Most damaging sort invades plants and destroys tissues from within
4. Has a spear on the mouth region which is thrust into plant cells. Salivary enzymes are then injected into the plant and the plant juices sucked in by the nematode.

Question 12

How do insects breath?

Answer 12

1. They do not have lungs
2. The have breathing holes called spiracles along their abdominal section leading to a breathing system (tracheae)

Question 13

How to control pests using spiracles

Answer 13

1. As they allow vapour to enter the tracheae of insects (and mites) they can also be blocked by formulations based on plant oils, for example sunflower oil or other sticky ingredients which smother the insect

Question 14

How to control pests using exoskeleton

Answer 14

1. Can be attacked by chemical which dissolve its waxy coating such as natural fatty acids

Question 15

How to control pests using the digestive system

Answer 15

1. Stomach acting pesticides can be eaten and poison the pest e.g. slug pellets

Question 16

How to control pests using multiple controls at once

Answer 16

Synthetic pyrethroid deltamethrin is a stomach poison but also acts on the outer skin or cuticle of the caterpillar