3.Pests

Question 1

Give 4 methods of pest feeding.

Answer 1

• Biting mouthparts (vine weevil, rabbit, deer)
• Piercing mouthparts (whitefly)
• Rasping mouthparts (molluscs)
• Sucking through tubular stylet (black bean aphid)

Question 2

Describe the damage done by Large cabbage white butterfly,

And methods to minimise.

Answer 2

• Caterpillars do the damage
• Leaves of brassicas, nasturtiums are gradually eaten away
• Eventually completely defoliated
• Physical = Cover crops with fine netting to prevent adult butterfly laying eggs
• Cultural = Manually wash of off eggs
• Provide alternate host
• Encourage blue tits by building nests
• Biological = Nematode sprayed on to caterpillar infested leaves

Question 3

Outline the lifecycle of the cabbage white butterfly.

Answer 3

• Spring - butterfly emerges from pupa
• Females lay 20-100 yellow/skittle-shaped eggs on underside of brassica leaves
• 2 Weeks: eggs hatch into caterpillar larvae which feed on the leaves and
• June larvae form a pupa (attach to woody stem with silk threads)
• Autumn adult emerges - 2nd Gen
• 2nd gen pupa over-winters

Question 4

Describe the damage done by black-bean aphid

And methods to minimise.

Answer 4

• Most commonly damaged are broad beans
• Shoots weakened by the aphids sucking phloem
• Aphids secret sugary liquid (honeydew) that can get infected by sooty mould (Blocks out light, preventing photosynthesis)
• Growth is affected and seed production dramatically reduced
• Biological = by encouraging predators ladybirds, lacewings, hoverflies
• Chemical = Spray with insecticide containing Pyrethrum, or natural fatty acids (Breaks down outer waxy cuticle)
• Cultural = Removal of host plants

Question 5

Outline the life cycle of black bean aphid

Answer 5

• Eggs overwinter on woody host e.g. Euonymous europaeus
• Spring: female nymphs emerge, feed on winter host
• At maturity they grow wings and fly to summer host such as beans
• Females give birth to many live young (5 per day)
• In autumn these live young include males and along with females they fly back to winter host to mate and lay eggs

Question 6

Describe the damage done by glasshouse whitefly.

And methods to minimise.

Answer 6

• Attacks a wide range of food and flower crops
• Rapid reproduction - introduced from tropics
• Stylets - Honeydew on foliage which attracts black sooty mold and prevents photosynthesis
• Biological – Encarsia formosa parasitic wasp
• Sticky yellow sheets hung above plants to trap whitefly
• Quarantine new plants/ check leaves
• Chemical – Pyrethrin and fatty acids

Question 7

Outline the lifecycle of glasshouse whitefly.

Answer 7

• Adult lays eggs Eggs – 200 minute white rugby-ball shaped in circular pattern on under side of the leaf
• Eggs turn black Hatch into nymphs
• Which then turn into flat scales
• 3rd instar Pupa and flying adult emerge
• Adult Lays eggs again 3 days later

Question 8

Describe the damage done by vine weevil

And methods to minimise

Answer 8

• Larvae live in soil and attack roots and tubers
• Adults emerge at night and eat irregular wholes in leaves
• Damage grape vines, and tubers such as cyclamen and begonias
• Plants have slow growth wilt and die
• Cultural – encourage natural predators such as birds, shrews, frogs etc.
• Picking/shaking off adult weevils at night in summer
• Biological – nematodes can be used on larvae
• Chemical – Bug Clear Ultra vine weevil killer (ornamental plants in containers)

Question 9

Outline the life cycle of the vine weevil.

Answer 9

• Autumn Adults feed on leaves and then lay eggs in soil or compost next to roots
• Larvae emerge white and legless with brown head
• Dec - Pupate in soil and adult emerges

Question 10

Describe the damage done by potato cyst eelworms (nemotodae)

And methods to minimise.

Answer 10

• Stunted potato/ tomato plant
• Yellow leaves turn brown and hang down
• Cysts on the roots
• Damage is patchy and increases year on year
• Use of resistant cultivars such as Maris Piper and use certified seed
• Remove host weeds (nightshade family)
• Five-year crop rotation
• Use young mustard crop as manure

Question 11

Outline the life cycle of potato cyst eelworm (nematode)

Answer 11

• Spring - Eggs hatch in and larvae invade roots and suck up cell contents
• Once larvae are fully developed they wriggle to outside of root and mate
• Female leaves head buried in root and swells
• Females change colour and form cyst which then drops from the root into the soil where it can survive many years with eggs inside

Question 12

Describe the damage done by peach-potato aphid

And methods to minimise

Answer 12

• Affect a wide variety of plants - prefer tender plants
• Sucking stylet - inject a digestive juice - distorts tissues
• Secrete honeydew - blocks stomata - attracts sooty mold - slows photosynthesis/growth
• Transfers viruses such as mosaic virus
• Physical = cover crop with fleece
• Biological = ladybirds, lacewings, hoverflies
• Small parasitic wasps
• Chemical = Insecticide containing Pyrethrum, or fatty acids

Question 13

Describe the damage done by two-spotted spider mite

And methods to minimise

Answer 13

• Affects a wide range of plants - few plants are completely immune
• Piercing and sucking mouth parts inject poison into leaf cells, causing localised death
• Yellowish mottling of the leaf
• Leaves lose green colour, dry up and drop off
• Spider mites and eggs can be visibly seen on underside of leaf
• Biological – introduce predatory mite
• Cultural – check all new plants
• In winter clean and disinfect glass house
• Chemical – spray insecticides containing fatty acids

Question 14

Describe the damage done by slugs

And methods to minimise.

Answer 14

• Feeds with radula and can scoop out cavities.
• Completely eat young seedlings
• Irregular holes in plants, leaves, roots, tubers, bulbs
• Leave a slime trail from undulating foot

Grey field slug, large black slug, garden slug

• Biological - Parasitic nematodes watered in spring, penetrate the slug and release bacteria (best for underground infestations)
• Physical - Place traps such as scooped out citrus halves, jars filled with beer
• Hand pick with torch
• Copper tape around pots
• Cultural - Encourage predators, hedgehogs, frogs and thrushes
• Chemical - Slug pellets, using metaldyhide (adult) or aluminium sulphate (young slugs)

Question 15

Outline the lifecycle of a slug

Answer 15

• Hermaphrodite (both sexual organs)
• Spring/summer - mate and lay clusters of up to 50 pearl-like eggs in rotting vegetation or under pots

Question 16

Describe how insects breathe.

Answer 16

• Insects breathe through holes in their abdomen called spiracles which lead to an internal breathing system of tracheae.
• There are 4 spiracles along the abdomen
• It is these that can be blocked by chemical control methods

Question 17

Name 3 entry points for insecticides into insects

Answer 17

• Waxy exoskeleton/cuticle can be broken down by fatty acids
• Spiracles allow chemicals in or are blocked by sticky pesticides
• Digestive systems (via the mouth) take in poison to stomach
• E.g Acetamprid - foliar spray used on ornamental plants against aphids

Question 18

Examples of pests have a winter host?

Answer 18

• Black bean aphid - Euonymus europaeus
• Peach potato aphid – Prunus spp

Question 19

Name i) a glasshouse pest ii) an outdoor pest

Answer 19

• 2-spotted spider mite /Glasshouse whitefly
• Rabbits /Vine weevil /Slug

Question 20

Give example of piercing/sucking pest.

Answer 20

• Aphids. Thread their mouth parts through intercellular spaces, tap into the plant’s vascular system, and feed by withdrawing sap from the phloem.

Question 21

Give example of raspers.

Answer 21

• Molluscs. Rasping, scraping or slicing the surface of the plant tissue and sucking out the fluids from the ruptured cells.

Question 22

Examples of pests that causes damage by biting.

Answer 22

• Vine weevil
• Deer
• Rabbit
• Caterpillars

Question 23

Definition of a pest

Answer 23

An organism belonging to th animal kingdom who’s activities have an adverse effect on plants

Question 24

Key effects of pests on affected plants

Answer 24

• Reduce plant vigor - crops/flowers are reduced
• Reduced decorative effect of ornamental plants
• Food may become unpalatable due to excrement
• May secrete ‘Honey dew’ causing soot mold/reduce photosynthesis
• May transmit disease/ viruses

Question 25

What does complete **metamorphosis** mean?

Answer 25

Complete change from an **immature** form to an **adult** form in **two or more distinct stages** - egg, larva (caterpillar), pupa (inactive) and adult.

Question 26

List key types of **Pesticide**

Answer 26

* **Molluscicides** - Kill molluscs, these can never be fully eradicated, efforts should be concentrated on protecting the most vulnerable plants (metaldehyde/aluminium sulphate) * **Insecticides/acaricides** - Used against insect and mite pests (contact/systemic/spiracles)

Question 27

Which **Mammal** does the most damage in the garden?

Answer 27

Rabbit, grey squirrel mole deer **Rabbit :** * **0.5kg** of plant food a day, turf and cereal crops worst affected. Also eat vegetable, bulbs and perennials * Can **reproduce quickly** * Control is the **responsibility of the landowner** * Physical= **Brick walls** or wire fencing, buried 30cm underground and facing outwards at an angle * Physical = **Sturdy plastic** **guard** around trees * Chemical - Repellent such as **ammonium sulphate** sprayed on bedding displays * Use plants **not attacked** by Rabbits