Pests Flashcards
What is the definition of a plant pest?
Any insect or animal that causes unacceptable levels of damage to cultivated plants, making them unsuitable for the purpose of which they were grown. Pests may affect the aesthetic value or the crop yield.
Why do pests need to be controlled?
Commercially growers can lose a lot of money if crops fail due to pests.
What are the 3 methods that pests feed on plant material?
- Piercing/sap sucking - aphids & whitefly.
- Biting - caterpillars, beetles & rabbits.
- Rasping - Slugs. Rarest of 3 methods.
How do insects breathe?
Insects breathe through holes called spiracles along their abdomen.
These spiracles connect to a network of tracheae (air passages or tubes) which allows oxygen to permeate all tissues. Spiracles can be closed by valves.
Why is it important to understand the biology of pests and how they breathe and reproduce?
Understanding how pests breathe and reproduce helps us in choosing a control method and timing of these methods.
Which pests can be managed by attacking their breathing mechanism?
Red spider mite, aphids and white fly.
How can you control pests by restricting their breathing?
Refined plant oils block the breathing pores. (Spiracles).
Oils are also used on fruit trees and bushes to kill overwintering eggs.
Other chemicals such as natural Pyrethrum or Deltamethrin as act as a nerve toxin which affects movement and breathing.
What do fatty acids do?
Fatty acids (insecticidal soaps) dry out the insect cuticle so desiccation is the cause of death. Most affective on soft bodied insects like aphids.
What is diatomaceous earth?
A powdery natural occurring soft sedimentary rock.
Dust made from diatomaceous earth abrade insect cuticle and make them susceptible to dehydration.
What control method can you use the biology of flying/winged insects to reduce numbers?
Trap them with yellow sticky traps placed at flying height.
What should we do to manage nocturnal pests?
Pick them off at night time - eg. Vine Weevil and slugs.
What is a pheromone trap?
Pheromone traps monitor populations and allow lifecycle to be broken at the point when the male is searching for the female.
Pheromone traps contain the odour of females and will trap the males.
Pheromone traps main use is to indicate when is the best time to use sprays - ie. Codling moth.
Give 3 examples of how knowledge of lifecycle of pests can help us manage them and their damage?
Plant at time of year to avoid when pest is active. Eg. autumn sown broad beans against black bean aphid.
Apply physical barrier to prevent pest laying eggs. Eg. Brassicas protected from cabbage white butterfly.
Target immobile stage for removal - eg. remove eggs and lifecycle is broken.
Which insect overwinters on Vibernum opulus?
Black bean aphid.
What are Glue Bands used for and how?
Glue bands applied to the trunks and stakes of fruit and ornamental trees to prevent wingless females of winter moths and similar species reaching the branches of the trees and laying their eggs.
Bands must be kept sticky and in position between November - March.
Barrier glue can also be used around pots and greenhouse staging to deter vine weevil. Sticky traps combined with a chemical attractant.
What are the two types of insecticides?
Systemic or Contact
What are systemic insecticides best used for?
Best for sap suckers, as the insecticide is taken up through the plant - then when the insect sucks the sap it is poisoned.
How do Contact Insecticides work?
They depend on good plant coverage. The insecticide is absorbed by the insect body or is eaten.
What are the two distinct types of insect lifecycle?
Complete and incomplete.
What is Complete Metamorphosis?
It means that there is a complete difference/change between the young and the adult.
- Egg
- Larvae (caterpillar/maggot/grub)
- Pupa
- Adult
Give 6 examples of insects with a complete lifecycle?
Ladybird Moth Butterfly Flies Vine Weevil Beetles
What is incomplete metamorphosis mean?
Incomplete metamorphosis means there is more of a gradual change between the young and the adult.
After hatching the younger insect gets bigger and bigger and sheds it’s exoskeleton several times. The adult may or may not have wings.
There are 3 main stages to incomplete metamorphosis.
- Egg
-Nymphs (bigger and bigger)
-Adults
Give 4 examples of insects with an incomplete metamorphosis life cycle?
Aphids
Earwigs
Crickets
Cockroaches.
What is the chemical control of pests?
Use of pesticides to reduce pest problem. They may be synthetic or naturally occurring compounds. They may be applied directly to the pest or to the plant, and then ingested from the sap by the pest
What is the physical control of pests?
The physical removal or the exclusion of pests.
Eg. Netting/barriers/traps.
Pinching out bean shoots covered in aphids and removing them.
Squishing aphids with fingers, or washing off with a powerful jet spray of water.
What is the biological control of pests?
Use of natural organisms which prey on the pest and reduce it’s numbers.
Biological control may be parasitic wasps, nematodes, mites.
The garden has lots of natural biological controls such as ladybirds eat aphids and ground beetles will eat slug eggs.
The gardener can introduce biological control to an enclosed environment in the greenhouse.
What is Integrated Pest Management? (IPM)
A pest control strategy that relies on multiple control practises.
Population levels are monitored and action is taken. Usually organic methods are favoured before chemical control but this depends on the scale of the problem.
What damage can rabbits be responsible for?
Rabbits can be responsible to a huge loss in agricultural and horticultural crops, including herbaceous plants, young trees, shrubs and vegetables.
They will eat the foliage, shoot tips and even bark.
Trees can be ring barked, where the bark is gnawed away the full circumference of the tree.
Young turf and seedlings will also be eaten.
They can chew through fencing and damage planting by digging/burrowing.
They can reach a height of 50cm stood on hind legs.
How can you physically control rabbits?
Barriers, wire mesh fencing or brick wall. With 30cm underground so that they can’t tunnel underneath. Ideally 1.2metres in height. Gates need to be rabbit proof too.
Electric fence.
Tree guards 60cm high advised for newly planted trees or shrubs
Surround susceptible plants with netting.
What chemical methods of control are there for rabbits?
Repellent chemicals sprayed on bedding /young trees. Aluminium ammonium - has a bitter taste so not suitable for edible crops which are close to harvesting.
What cultural control can be used to deter rabbits?
Planting resistant species such as Agapanthus, dahlia, snowdrop, clematis, berberis.
What professional techniques can be used to deter rabbits?
Rabbits can be killed by shooting, gassing or trapping.
What host plants does the Peach Potato aphid like?
The peach potato eats a wide variety of plants including fruits, flowers and vegetables.
It’s host in winter is lettuce and brassicas in egg form.
In summer it is a particular pest of the potato.
Also helps to transmit the Potato leaf curl virus.
What does the Peach Potato aphid look like?
2.6mm long.
Mostly pale green. (sometimes yellow & pink)
Soft pear shaped bodies.
Winged and wingless forms.
What damage does the Peach potato aphid do, and what are the signs?
They are sap suckers.
Large colonies will reduce plant vigour.
Aphids can also transfer virus’ from plant to plant.
They have an incomplete metamorphosis, so will shed their exoskeletons leaving white flakes on the leaf below, which looks like dandruff.
They excrete honey dew which ants will farm.
What damage should you look for when checking to see if you have got Peach Potato aphids?
Sap suckers.
Stunted growth.
Shiny leaf surface - honeydew
Black leaf surface - sooty mould griws on sugars from honeydew.
Distorted leaves
Distorted leaves and growth - indicating a virus.
What damage should you look for when checking to see if you have got Peach Potato aphids?
Stunted growth.
Shiny leaf surfaces (honeydew)
Cream/white ash like substance of exoskeletons molted
Black leaf mould, which is sooty mould which grows on the sugar rich honeydew and prevents photosynthesis.
Distorted leaves - aphids destroy the balance of plant growth regulators and cause malformation of the growth tips.
Distortion and stunted growth indicating a virus. Aphid transmitted virus can result in plant death.
How can you control Peach Potato Aphids with biological control?
Biological -
Outdoors control with natural predators such as ladybirds, lacewing, hoverfly.
Greenhouse biological control - Aphidius - a parasitic wasp.
How can you control Peach Potato Aphids with chemical control?
Chemical control of Peach potato aphid.
Plant oil spray which blocks spiracles.
Fatty acids - soap sprays dries out cuticles and can block spiracles.
Deltamethrin - affects nervous system
How can you control Peach Potato Aphids with cultural control?
Cultural control of Peach potato aphid
Hand picking/squashing. Strong water jet to wash off.
Remove weeds in Brassica family - Capsella bursa-pastoris.
Use fleece to stop them spreading to susceptible plants.
Fine mesh over vents in greenhouse.
What preventative methods are there to help control spread of Peach potato aphid?
Preventative methods of controlling the Peach potato aphid -
Quarantine infected plants
Fleece barrier
Regular checks.
Encourage natural predators.
Do not overfeed as they like sappy growth.
Describe what the black bean aphid looks like?
Black 2mm long with pear shaped bodies.
Often referred to as blackfly, though it is not a fly.
They are piercing sap suckers.
What is the Black Bean aphid’s host plants?
Broad beans - common early in season. French beans Runner beans Nasturtium Dahlias In Winter - Philadelphus, Euonymus and Vibernum.
What damage/symptoms are caused by Black bean aphids?
Commonly damage broad beans, but also runner and french beans.
Aphids have a sucking action and excrete honey , which can lead to sooty mould.
Plant growth stunted.
Seed production can be reduced. Broadbean pods do not develop well.
Misshapen leaves and pods form, as aphids disturb the balance of plant growth.
Sooty mould.
Aphids seen in a cluster at the soft growing tips.
Ash like cast skins - exoskeletons.
Describe the lifecycle of the Black bean aphid?
Overwinters in egg form on plants like Euonymus or Viburnum species.
All female nymphs emerge and feed on the host shrub, until winged females emerge and fly to the summer host - the broad bean (or french or runner bean).
Female aphids will feed and reproduce A sexually, until food source runs out, then more female winged Aphid’s will emerge and fly to a new host.
In Autumn, male and female winged aphids will fly to winter host where it will lay it’s eggs.
How can you control the Black Bean aphid biologically?
Outdoor natural predators - Ladybirds, lacewings and hoverflies.
In greenhouse - parasitic wasp.
How do you control Black bean aphid with chemicals?
Plant oil sprays which will block spiracles.
Fatty acids - soap sprays will dry out cuticles and may block spiracles. Particularly affective as they have a soft body.
Deltamethrin attacks nervous system.
What preventative methods can be used for Black bean aphid?
Quarantine infected plants to avoid spread.
Fleece barrier.
Regular checks
Encourage natural predators.
Do not overfeed, as they love sappy new growth.
