2103 - Plant Pests Flashcards
What is a Pest?
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.
Common RHS Pest list
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
Damage done / Control - Rabbits
Dig Holes, Strip bark from trees, eat crops
Breed in Spring, bulk up quickly, rapidly multiply
Controls:
Rabbit Proof Fencing (Cultural)
Hunting (Physical)
Damage done / Control - Moles
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)
Damage done / Control - Deer
Eat Leaves, shoots and stems up to a level hey can reach.
Controls:
12ft fence
Culling / Hunting
Damage done / Control - Pigeon
Leaf and Crop damage
Controls:
Netting
Hunting / Shooting
Insect body parts (grasshopper)
- Head
- Thorax
- Abdomen
- Front wing, Hind wing
- Spircales (breathing/gas exchange)
- Invertebrates have an Exoskeleton
Points of Entry for Insecticide
Surface insecticide - for chewing insects
Translocated insecticide - sap sucking insects
Contact insecticide - (fatty acids) Block up Spircales
Insect Growth - Incomplete Metamorphosis
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
Insect Growth - Complete Metamorphosis
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
Types of Insect Damage
- Sap Sucking (Aphid)
- Rasping (Slug)
- Chewing (Adult Vine Weevil)
Sap Sucking damage and control
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.
Sap Sucking - Black Bean Aphid
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.
Sap Sucking - Black Bean Aphid life cycle
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.
Sap Sucking - Black Bean Aphid Damage
- Stunted Growth
- Distroted Growth
- Reduced photosynthesis due to sooty moulds
- Secondary viral infections
Sap Sucking - Black Bean Aphid Controls
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
Sap Sucking - Glasshouse Whitefly
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
Sap Sucking - Glasshouse Whitefly Damage
- Stunted Growth
- Distroted Growth
- Reduced photosynthesis due to sooty moulds
- Secondary viral infections
Sap Sucking - Glasshouse Whitefly Control
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)
Sap Sucking - Two Spotted Spider Mite
(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
Sap Sucking - Two Spotted Spider Mite Damage
- Localised death of leaf mesophyll cells, resulting in mottling on the leaf
- large infestation can kill off leaves and whole plants
Sap Sucking - Two Spotted Spider Mite Control
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
Sap Sucking damage and control
- 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
Chewing - Cabbage White Butterfly
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.
Chewing - Cabbage White Butterfly damage and control
- 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
Chewing - Vine Weevil
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
Chewing - Vine Weevil damage and control
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
Rasping Molluscs - Slugs and Snails
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.
Rasping Molluscs - Slugs and Snails damage and control
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
Potato Cyst Eelworm
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.
Potato Cyst Eelworm - control
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.
