2103 - Plant Pests

Question 1

What is a Pest?

Answer 1

A multi-celled Organism belonging to the Animal kingdom that has the ability to attack and cause damage to any part of a plant.

Pests can be vertebrates or invertebrates.
Pest use the plant for food or shelter.

Question 2

Common RHS Pest list

Answer 2

Rabbits
Deer
Pigeons
Cabbage White Butterfly
Buttefly Larvea
Black Bean Aphid
Peach Potato Aphid
Two Spotted Spider Mite
Glasshouse Whitefly
Vine Weevil
Slugs, Snails
Potato Cyst Eelworm

Question 3

Damage done / Control - Rabbits

Answer 3

Dig Holes, Strip bark from trees, eat crops

Breed in Spring, bulk up quickly, rapidly multiply

Controls:
Rabbit Proof Fencing (Cultural)
Hunting (Physical)

Question 4

Damage done / Control - Moles

Answer 4

Dig through Lawns, leave big mound of soil (mole hills)
Most common in Hearty Loam Soils

Controls:
Humane Traps, check twice a day (Cultural)
Physical barriers
Smokes
Ultra-Sonic deterrents
Dig up tunnels and remove pest (Physical)

Question 5

Damage done / Control - Deer

Answer 5

Eat Leaves, shoots and stems up to a level hey can reach.

Controls:
12ft fence
Culling / Hunting

Question 6

Damage done / Control - Pigeon

Answer 6

Leaf and Crop damage

Controls:
Netting
Hunting / Shooting

Question 7

Insect body parts (grasshopper)

Answer 7

• Head
• Thorax
• Abdomen
• Front wing, Hind wing
• Spircales (breathing/gas exchange)
• Invertebrates have an Exoskeleton

Question 8

Points of Entry for Insecticide

Answer 8

Surface insecticide - for chewing insects
Translocated insecticide - sap sucking insects
Contact insecticide - (fatty acids) Block up Spircales

Question 9

Insect Growth - Incomplete Metamorphosis

Answer 9

3 stages:
Egg, Nymph, Adult
Nymph stage resembles the adult. There can be several Nymph stages with growing and shedding of the Exoskeleton.

Nymph = Juvenile stage, growing not capable of sexual reproduction

Question 10

Insect Growth - Complete Metamorphosis

Answer 10

4 stages:
Egg, Larva, Pupa, Adult (Butterfly)
The Larval stage is usually characterised but ravenous foraging, pupa by inactivity.

Classic example:
Egg, Caterpillar, Cocoon (chrysalis), Butterfly

Question 11

Types of Insect Damage

Answer 11

• Sap Sucking (Aphid)
• Rasping (Slug)
• Chewing (Adult Vine Weevil)

Question 12

Sap Sucking damage and control

Answer 12

Sap sucking insect, Use mouth parts (Stylet) to access sap in the plant. resulting in:

• Loss of Vigour
• Stunted Growth
• Distorted Foliage and Shoots
• Disease Transmission

Chemical Control - Translocated Insecticide.
Enters plants Phloem, transported around the plant, insect eats it and dies.

Question 13

Sap Sucking - Black Bean Aphid

Answer 13

Black Bean Aphid
Incomplete Metamorphosis
Egg, Nymph (series of instars), Adult

Aphid eats Phloem sap, their waste matter is Honey Dew which encourage Ants, who will then protect the aphid colony. Honey Dew encourages mould.

Question 14

Sap Sucking - Black Bean Aphid life cycle

Answer 14

Eggs are laid in crack, stems and twigs. Eg. Sambucus nigra or Euonymus europaeus - Spindle

Eggs hatch in Spring, wingless female feed on host plant.

Winged Males produced shortly after which fly to summer host plant. Typically Broad Beans, and Dahlias

Adults produced in late summer, fly to winter host and repeat the life cycle.

Question 15

Sap Sucking - Black Bean Aphid Damage

Answer 15

• Stunted Growth
• Distroted Growth
• Reduced photosynthesis due to sooty moulds
• Secondary viral infections

Question 16

Sap Sucking - Black Bean Aphid Controls

Answer 16

Physical:
Hose of populations from plant tips
Snap off tips of infested plants and destroy

Cultural:
Sow Early cultivars of beans so the young tips are not as susceptible to attack when the aphids arrive
Remove Winter hosts - Sambucus nigra

Biological:
Encourage ladybirds, bluetits, lacewings, hoverfly larvae

Chemical:
Contact insecticide - Fatty Acids SB Plant Invigorator

Question 17

Sap Sucking - Glasshouse Whitefly

Answer 17

Glasshouse Whitefly
Incomplete metamorphosis
Egg, Nymph (series of instars & puparia), Adult

Lots of eggs laid on the underside of a leaf
1st Instar, mobile sapsucking. 2nd,3rd,4th are immobile but sap-sucking which exude honeydew.

Pupal Stage, followed by Adult mostly female, can reproduced A-sexually.

Host includes Tomatoes, Pelargoniums
Overwinters on Chickweed - Stelalria media

Question 18

Sap Sucking - Glasshouse Whitefly Damage

Answer 18

• Stunted Growth
• Distroted Growth
• Reduced photosynthesis due to sooty moulds
• Secondary viral infections

Question 19

Sap Sucking - Glasshouse Whitefly Control

Answer 19

Cultural/Physical:
Remove host plants eg. Stellaria media (chickweed)
Use yellow sticky traps

Bioglogical:
Encarsia formosa, parasitic wasp lays an egg inside larvae

Chemical:
Fatty Acids (SB Plant Invigorator)

Question 20

Sap Sucking - Two Spotted Spider Mite

Answer 20

(Arthropod not insect)
Sap-Suckers found on the underside of leaves, but are very small and difficult to see.
Infestations can cause a ‘webbing’.

Complete Metamorphosis
Eggs, Larvea, Nymphs, Adults

Multiplication potential is very high, hibernate over winter

Question 21

Sap Sucking - Two Spotted Spider Mite Damage

Answer 21

• Localised death of leaf mesophyll cells, resulting in mottling on the leaf
• large infestation can kill off leaves and whole plants

Question 22

Sap Sucking - Two Spotted Spider Mite Control

Answer 22

Physical:
Remove and Destroy badly infected plants

Cultural: Increase humidity in glasshouse by dampening downing and misting (discourage two spotted mites)
Glasshouse hygiene, remove overwintering sites

Biological: Predatory mites introduced at first sight of infestation.

Chemical: Acaricides - Fatty Acids

Question 23

Sap Sucking damage and control

Answer 23

• Chewing of foliage and young stems (defoliate)
• Can destroy plants
• reduced photosynthesis resulting in
• Stunting
• Root damage caused by vine weevil larvae
• eventually plant will become unstable, die

Contact insecticides, Vine Weevil larvae can be controlled with nematodes

Question 24

Chewing - Cabbage White Butterfly

Answer 24

The caterpillar stage cause the damage, voracious appetite and can defoliate plants rapidly.

Host plants: Brassicas, cabbage, cauliflower, Brussel sprout

Complete Metamorphosis
Egg, Larva (caterpillar), Pupa (chrysalis), Adult

Overwinters as a Pupa, but two further generations can develop during the growing season.

Question 25

Chewing - Cabbage White Butterfly damage and control

Answer 25

- chewing of foliage, of Brassicas - can quickly destroy plant Biological/Cultural: Encourage birds that will eat the larvae, by providing shelter such as hedgerows, also providing food. Introduce parasitic wasp which lays eggs in larvae. Physical: Netting or Fleece over crops can prevent the adults laying eggs on the crop plants Removing winter host Brassicas. Pick off by hand Chemical: Pyrethrin contact insecticides, suitable for edible crops Biological Insecticide: Bacillus thunringiensis spray cause fatal bacterial infections in the larvae causing death

Question 26

Chewing - Vine Weevil

Answer 26

Adult Vine Weevil will cause damage to the edges of leaves, but the worst damage is caused by the larvae which destroy roots of plants, such as Heuchera spp. Particularly in container grown plants. Complete Metamorphosis Egg, Larva, Pupa, Adult

Question 27

Chewing - Vine Weevil damage and control

Answer 27

Adult stage - chewing edges of leaves Larval stage - Chewing roots underneath the soil. Plants become stunted, wilting, chlorosis, unstable in the ground, and death. Physical: hand picking the larvae when potting plants, and removing adults if seen Cultural: Purchasing clean, non infected plants. Removing debris sheltering sites around plants Biological: Vine Weevil specific nematodes, attacks larval stage (timing of application is vital, as nematodes will only survive at a specific temperature 5c Autumn. Chemical: Soil drench applied systemic insecticide to control larvae - Acetamiprid

Question 28

Rasping Molluscs - Slugs and Snails

Answer 28

Host plants are wide ranging and varied. Dahlia, Narcisuss, Hosta Most damage is in early spring and summer, particularly in wet weather. Feed above ground on seedlings and young shoots/leaves. Below ground feeding on bulbs, corms and tubers. Eggs are laid in Spring, young slugs develop and feed during the summer but hibernate in winter. Lives up to 4 years.

Question 29

Rasping Molluscs - Slugs and Snails damage and control

Answer 29

Rasping mouthparts, holes will be regular and occur central with the leaf. Slime trails can identify damage as slug related. Common on Dahlias, Hosta spp. and Lettuce Physical: Slug traps can be laid at night and disposed of in the morning. Beer traps, shallow dish filled with beer, attracts and drowns slug. Night patrol. Cultural: Cultivating soil frequently, exposing slugs and egg to predators and weather. good garden hygiene removes possible breeding sites. Biological: Nematodes can be applied, not in too wet or dry weather. most appropriate in spring and autumn. Chemical: Slug pellets. Ferramol

Question 30

Potato Cyst Eelworm

Answer 30

Hosts include Potatoes and Tomatoes (Solanum spp.) Microscopic soil borne eelworm Leaves become yellow and undergo premature die-back. Due to root feeding eelworm. Can survive in the soil for many years without a host to infect. Stimulated to growth with chemicals release when host plant is in close proximity.

Question 31

Potato Cyst Eelworm - control

Answer 31

Physical: Good tool hygiene Good garden hygiene (soil movement) Control Solanum weed spp. Cultural: Early cropping varieties, or resistant cultivars Maris Piper So Sticky nightshade as a trap, as the larvae cannot develop on this plant.