2103 - Natural Balances Flashcards
Natural Balances
Organisms, considered pests, are kept in control by their natural predators, parasites and pathogens.
This balance is often disturbed due to gardening practices, eg the use of pesticides.
Beneficial Organisms in Pest Control
Animals which naturally occur in the Garden and prey on plant pests.
- Ladybirds
- Hoverflies
- Lacewings
- Frogs
- Hedgehogs
- Birds
Methods to restore Natural Balance in a Garden
- Minimise use of pesticides (last resort)
- If used, selective pesticides to avoid harm to a wide range of organisms
- Grow wide range of plant species
- incorporate wide range of features, beneficial to organisms. Hedges, Ground Cover, Ponds, Meadows, Woodland
- Avoid excessive today/neatness in the garden, plant debris provides shelter/food
- provide a habitat/shelter for beneficial insects
Natural Predators - Ladybirds
Ladybirds eat Black Bean Aphids
- avoid use of insecticides as these can kill ladybirds (selective only if they must be used)
- don’t tidy leaves or cut back herbaceous plants until late winter. (Adult ladybirds over winter there for protection)
- Grow plants that provide them with pollen eg. Buddleja spp. (or open centred flowers)
- Don’t remove all weeds, as Laybirds can feed form the pollen
- insect hotels for overwintering
Achilea filipendulina, Ajuga reptans
Natural Predators - Lacewings
Common Green Lacewings control many pests. However the Adult of the species live on nectar, pollen and honeydew.
The larvae are voracious predators though.
-Larvae live for 2-3weeks then pupate and live as an adult for 5-6weeks.
- Avoid use of insecticides
- provide shelter for overwintering. (sheds, dry crevices, leaf litter)
- Plant pollen / nectar rich plants
Achilea filipendulina
Natural Predators - Hoverfly
Efficient pollinators, many species have predatory larvae which feed on aphids and sap sucking pests.
-Grow Nectar rich plants which adults feed on
Achillea filipendulina
- Open centred flowers to provide pollen source.
- Avoid applying pesticides, especially when the plants are in flower
- overwinter salter such as bug hotel
Natural Predators - Frogs
Feeds on Moths, mosquitos, slugs, snails.
- encourage by providing a pond with shallow sides for access.
- native planting
- hibernating areas
Natural Predators - Hedgehogs
Eats Slugs, Beetles and other insects
- Encourage by leaving a habitat box for them
(old, weathered wood) - provide access through garden walls/fences
- loose woodpiles
- always check bonfires before lighting
Natural Predators - Birds
Various birds (especially Thrushes) eat snails, slugs, caterpillars, aphids
- encourage by planting suitable nesting trees and shrubs (hedgerow)
- Shrubs / Trees with autumn and winter fruit (Ilex)
- provide bird baths and food, particularly over winter
Natural balances cont…
- diversity is the key to natural balance
- more complex food web, prevent large population swings found in monocrops
- natural balance philosophy accepts a level of damage or loss in the crop, in return for a stable environment
- reduced requirement for human intervention
(if you want ladybirds, you must first have aphids)
General practice examples
- Provide companion plants that will attract useful predators.
eg. Achillea filipendulina (ladybird, lacewings, hoverfleis) - Provide sites or plants to encourage overwintering
eg. leaf litter, suitable shrubs (Crataegus monogyna)
Maintain the natural balance…
- Crop Rotations (not mono)
- increase insect diversity by growing diverse plants
- wild areas for habitat, log-piles, ponds (shallow sides) leaf litter
- biological control rather than pesticides
eg. Encarsia formosa (glasshouse whitefly wasp) - no dig to encourage healthy soil life
- Nesting and overwintering sites, damp shady corners, hedgerow, nests hedgehog boxes
Disturbing the natural balance
- Excessive use of chemical controls
- cutting hedges and trees during nesting season
- non-sterile tools and machinery
- poor tool hygiene when moving sites
- composting infected / diseased material
- over use of fertiliser to promoting soft growth
Reducing the impact of pesticides
- spray on clam days to reduce drift
- spay affected areas only, targeted
- Selective pesticides, where possible
- Avoid spraying in the middle of the day when insects are most active, or near open flowers
- Never spray near watercourses
- Follow manufactures guildlines
minimise Pesticide use by…. physical, cultural, bio
Bio
Encarsia formosa wasps to control glasshouse whitefly
Physical
Hand controlling pests, eg directed methanol swabs to control woolly aphid in glasshouse
Cultural
Correct management to avoid build up in the first place.
Pinch out broadbean tip to discourage blackfly
