R2103 - Maintaining plant health Flashcards
(97 cards)
1
Q
What is physical control?
A
Physical control is the use of a barrier or a trap to either prevent the growth of weeds or to protect plants from being attacked by pests.
2
Q
What is cultural control?
A
Cultural control is the use of good horticultural practices or a change to the growing environment, which results in better control of weeds, pests, diseases and plant disorders.
3
Q
What is biological control?
A
Biological control is the use of ‘produced’ or naturally occurring predatory or parasitic enemies to control pests.
4
Q
What is chemical control?
A
Chemical control is the use of a chemical substance, organic or inorganic, intended to prevent or kill a destructive weed, pest or disease.
5
Q
State possible benefits and limitations of physical control. (Need 2 for exam)
A
Benefits
- Most are environmentally friendly and do not damage the pest, plant or soil.
- Many prevent the pest reaching the plant
- Fences and fruit cages can remain in place for many years with little or no maintenance
- Pheromone traps are monitors of pest populations, giving an indication of when insecticide controls will be most effective
- Safer for the operator as no potentially harmful chemicals are used
- No build-up of resistance to the control method
Limitations
- They do not get rid of the pest and in some cases such as carrot fly the pest can remain in the soil
- Fences and fruit cages, are expensive to set up
- Knowledge of the life cycle of the pest is required
- Barriers can make access to the crop difficult
6
Q
State possible benefits and limitations of cultural control. (Need 2 for exam)
A
Benefits
- The methods fit in with general daily gardening routines such as regular weeding or feeding of plants
- Most are relatively easy to manage for example crop rotation, growing resistant cultivars or timing of sowing or planting.
- Rotation of crops causes a beneficial change in the fungal and bacterial population in the soil
Limitations
- May be time consuming
- May lack the rapid response that is seen when using pesticides
- The gardener has to be very alert to any changes in plant growth and aware of any pests and diseases before they become established
7
Q
State possible benefits and limitations of biological control. (Need 2 for exam)
A
Benefits
- It is non-toxic to humans and animals
- The number of predators and parasites increases naturally
- A balanced population of predators and parasites will exist side by side
- There is no build–up of resistant pests or diseases
- Avoids physical damage to crops
Limitations
- Gardener needs knowledge of the life cycle of the pest so that the predator is introduced at the right time
- The pest has to be present in sufficient numbers to support a population of predators
- Some biological control organisms require specific temperatures to thrive
- There may be some damage to the crop before the biological control can get the pest under control - Safe practice and environmental impact
8
Q
State possible benefits and limitations of chemical control. (Need 2 for exam)
A
Benefits
- Chemicals produce rapid control and can be pest specific
- The chemical can target the problem at the most susceptible phase in its life cycle if used correctly
- Products are easily obtained from garden centres
- Chemicals can be used as a preventative measure
Limitations
- Products can be dangerous to humans and animals
- Products can cause resistant strains of pests, diseases and weeds to develop
- Chemicals may cause damage to other plants in the area
- May cause harm to beneficial organisms
9
Q
Geo textiles, Cages and Fences
1.1 Physical control - Describe barriers and how risks to people and the environment can be minimised.
A
Barriers: plastic sheets, fleece, fences, cages
Plastic sheets - woven geotextiles Great for preventing weed growth. Allows the passage of water, nutrients and oxygen into the soil but prevent weeds from growing. Sheet is laid over bed or border with slits made for desired plants to grow. Minimise risks by safe disposal, do not burn but as toxic. Take to recycling centre.
Fleece - gives protection against pests in the vegetable garden. Covering plants blocks carrot fly, cabbage root fly and cabbage white butterfly from crops. Only effective if used in conjunction with a crop rotation system. E.g. carrot fly can lie dormant in the soil from one year to the next and would become trapped under the fleece, laying eggs on the new crop of carrots. Minimise risks by safe disposal, do not burn but as toxic. Take to recycling centre.
Fences - Can be used to keep rabbits and deer out of the garden as they can do a huge amount of damage nibbling bark on trees and shrubs and eating foliage, buds and crops. Sturdy wire mesh sunk 30cm into the ground, will also prevent digging holes underneath. Minimise risks by using correct tools and equipment when erecting. Dispose of all waste at a recycling centre.
Cages - Mesh cages protect soft fruits from birds. Wide range available on the market. They can be expensive but be homemade cheaply with stakes and bird/butterfly netting. Minimise risks by using correct tools and equipment when erecting. Dispose of all waste at a recycling centre.
10
Q
Pheromone and Sticky
1.1 Physical control - Describe traps and how risks to people and the environment can be minimised.
A
Pheromone traps - pheromones of some pest species such as codling moth, plum moth, pea moth, and raspberry beetle have been synthesised for use in pheromone traps. At correct time of year, dependent on the pest, traps are positioned either in the tree or amongst the crop. Male insects attracted by the pheromone, fly into the trap, expecting to find a female, but instead get caught on the sticky sheet. Risks - there are no risks to people or the environment associated with the use of pheromone traps.
Sticky traps - traps are made of yellow (attractive to insects) plastic strips, covered in non-drying glue. When suspended above plants, insect pests fly/jump onto them and are unable to escape. Useful for catching flea beetles, whiteflies, aphids, thrips, and fungus gnats. Risks - no real risks, just avoid touching the sticky grease or glue on the traps.
11
Q
Rotavating or digging
1.1 Cultural control - Describe rotavating & digging and how risks to people and the environment can be minimised.
A
Rotavating or digging - Do in autumn to expose soil pests such as leather jackets and cutworms to birds. Brings an improvement in soil structure, a good method of soil preparation before planting or sowing a crop on uncultivated ground. Annual weeds will be buried and killed e.g chickweed (Stellaria media) and groundsel (Senicio vulgaris) But their seeds may lie dormant in the soil for several years. Dig out and remove all perennial weed roots as they regrow quickly from small pieces. Risks - dispose of perennial weeds in local authority compost bin as weeds could be spread to other parts if put in home compost. Also if rotavation is carried out to the same depth each time then a soil pan could develop. Take care to use and maintain tools safely.
12
Q
Hoeing and hand weeding
1.1 Cultural control - Describe hoeing & hand weeding how risks to people and the environment can be minimised.
A
Hoeing and hand weeding - Carry out regularly whilst the weeds are small and before they set seed. Hoeing annual weeds is an effective method of cutting through the roots but it needs to be done on a dry, sunny day so that the weeds die off once cut. Risks - Spread of weed seeds or roots through compost. Use local authority bin. The roots of perennial weeds may be left in the soil and then re-grow. Try and remove all roots.
13
Q
Introduced predators and parasites
1.1 Biological control - Describe introduced predators & parasites and how risks to people and the environment can be minimised.
A
Introduced predators and parasites - Pests spread quickly in greenhouses and polytunnels where temperatures are higher than outside. E.g red-spider mite, very difficult to control. Biological controls has been developed using natural enemies to control glasshouse pests. These natural predators are released onto the infected plants, soil or potting compost to control the pests. Risk can be minimised by - Understanding both the pest’s and the predator’s life cycles in order to achieve reliable control - Choosing the most appropriate predator for the pest or disease - Taking care that environmentally useful animal species or insects are not subject to attack from the predator
14
Q
Indigenous garden predators and parasites
1.1 Biological control - Describe indigenous garden predators & parasites and how risks to people and the environment can be minimised.
A
Indigenous garden predators and parasites - indigenous species are present locally in wild plant communities in Britain. Garden pests may be controlled either by predators that eat the pest, or by parasites that lay their eggs inside the pest, such as nematodes. Growing a wide range of flowers and other plants in your garden is very useful as this will provide food and shelter for a wide range of beneficial insects, birds and pest eating mammals such as bats, shrews and hedgehogs. Installing a pond will encourage frogs and toads. Risks - no real risks. Consider the life cycles of pests and predators so a natural balance is created. Avoid being too tidy in the garden as old foliage, leaves, wood could be home to overwintering predators.
15
Q
Contact herbicides
1.1 Chemical control - Describe contact herbicides & how risks to people and the environment can be minimised.
A
Contact herbicides - Contact weedkillers are non-selective and non-residual and work simply by scorching off weed foliage. This makes the ready-to-use formulations ideal for controlling annual weeds and perennial weed seedlings growing in between garden plants, which can simply be protected using polythene, cardboard or an upturned bucket. They do not move around in the plant’s vascular system so are not able to reach the roots of perennial weeds such as couch grass or bind weed. They are only effective against annual weeds and perennial weed seedlings. An example is Roundup Speed Ultra RTU, containing acetic acid. Risks - Herbicides are damaging to the environment and should only be used as a last resort. Most weeds can be controlled by good cultivation techniques such as hoeing, mulching, mowing and digging. Read and carefully follow all instructions. Use protective clothing. Store safely and keep away from children and animals.
16
Q
Systemic weedkillers
1.1 Chemical control - Describe systemic weedkillers and how risks to people and the environment can be minimised.
A
Systemic weedkillers - are non-selective and non-residual. They differ from contact weedkillers in that when applied to the foliage the weedkiller moves down into the root system of the weed. This makes systemic weedkillers ideal for controlling deep-rooted perennial weeds. Path & Patio Weedkiller RTU containing Glyphosate. Risks - Herbicides are damaging to the environment and should only be used as a last resort. Most weeds can be controlled by good cultivation techniques such as hoeing, mulching, mowing and digging. Read and carefully follow all instructions. Use protective clothing. Store safely and keep away from children and animals.
17
Q
Check this
1.2 Explain the importance of natural balances in plant protection.
A
Gardens are ecosystems – a complex web of producers (plants), consumers and decomposers in a ‘natural’ habitat.
Understanding this can help to prevent, and to deal with, problems with plant health.
Not taking this fact into account can lead to pest and disease problems and wasted effort in trying to control them.
18
Q
1.2 Describe beneficial organisms (ladybirds, lacewings, hoverfly, hoverfly larvae, frogs, hedgehogs, birds)
A
ladybirds - 40 British species of ladybird beetle and almost all are predatory. Most familiar is the ‘red seven-spot ladybird’ Emerges from the soil in spring, mates and lays about 1,000 eggs throughout the growing season on the leaves of a range of weeds such as nettles and crops like beans. Larvae and adults feed on a range of aphid species
lacewings - lay several hundred eggs a year on fine stalks or the underside of leaves. Really useful predators as their hairy larvae eat aphids and mite pests, often getting into leaf folds where ladybirds cannot reach. Used as predators in commercial glasshouses.
hoverfly - Excellent pollinators.
hoverfly larvae - Many of the 250 British species lay eggs in the midst of aphid colonies, and their legless, light green coloured grubs (resembling small green maggots) consume large numbers of aphids.
frogs - contribute greatly to the control of slugs and ground-living insect pests. Create leaf, log and stone piles for cover. Make a pond.
hedgehogs - eat beetles, caterpillars and earthworms and slugs.Make small holes in the bases of fences so hedgehogs can easily move from garden to garden. Make shelters for overwintering: piles of logs, leaves or readymade shelters.
birds - contribute greatly to the control of horticultural pests. Bluetits eat caterpillars, aphids and scale insects. Install nest boxes to encourage then into the garden. Thrushes eat snails, leave flat stones as anvils for shell smashing.
19
Q
1.2 Give TWO examples of how beneficial organisms can be encouraged.
A
- Avoiding the use of organic and inorganic pesticides that may disrupt the life cycles of beneficial organisms
- Installing specific habitats such as nest boxes, hives, hedgehog boxes, log piles and insect hotels
- Growing plants that attract and support beneficial insects
- Tolerance of some aphids in the garden is necessary to encourage ladybirds as this is their main source of food
20
Q
1.2 List FOUR beneficial organisms, naming ONE distinct plant pest controlled by EACH
A
- Blue tits will control caterpillars in a garden
- Frogs will consume slugs
- Song thrushes will consume snails
- Lady bird, ladybird larvae and lacewing larvae will control aphids
- Lacewing larvae will control thrips
- Hoverfly larvae will control aphids
21
Q
1.2 Give TWO examples of how garden practices can disturb these balances, including the use of pesticides:
A
- Excessive use of inorganic pesticides particularly during the middle of the day when beneficial creatures are present (bees, ladybirds)
- Cutting hedges and other nesting sites for birds during the nesting season
- Use of non -sterile tools and equipment that can spread disease
- Composting infected or diseased plant material in the garden
- Over cultivation of soil reduces soil organism numbers and diversity.
22
Q
1.2 Describe TWO methods of increasing the diversity of wildlife in a garden to minimise the need for chemical pesticides.
A
- By growing a wide range of plants that will attract and support beneficial insects such as hoverflies and lacewings
- Installing specific habitats such as bird boxes to attract blue tits, hedgehog boxes, log piles and an insect hotel to encourage predators
- Construct a pond with sloping sides or a beach to attract frogs and toads that will eat slugs
- Avoid cutting back and tidying up herbaceous plants and grasses in the autumn as they will provide food and cover for beneficial insects and birds during the winter
23
Q
Include resistant cultivars
1.3 Describe how the selection of plants can help avoid plant health problems.
A
- Selection of resistant cultivars such as ‘Sarpo’ seed potatoes which are blight resistant. Cauliflower clapton F1 resistance to club root. Daucus carota ‘Flyaway’ resistant to carrot fly.
- Inspecting plant material for any obvious pests or diseases at the time of purchase
- Selecting plants that are suited to the particular growing conditions, aspect, soil type, pH and microclimate
24
Q
1.3 Describe TWO named examples of an appropriate choice of a plant for NAMED situations.
A
- acid soil Camellia japonica, Magnolia ‘Butterflies’
- dry shade Hellebore, Fatsia japonica, Pulmonaria officinalis, Cyclamen coum
- moist shade Galanthus nivalis (snow drop) Hosta ‘El Nino’
- alkaline soil Buddleja davidii, Lavandula ‘Baby Blue’
25
2.1 Describe what is meant by a weed.
A weed is a plant growing in the wrong place or out of place.
26
2.1 Describe how weeds cause problems.
Reduction of crop productivity occurs because of competition between the weed and the plant for water, nutrients and light.
Weeds may be alternative hosts to pests and diseases. White blister rust of Brassicaceae, the cabbage family and club root can also affect *Capsella bursa- pastoris (*shepherd’s purse) and *Cardamine hirsuta (*hairy bittercress) which are both in the cabbage family.
The presence of weeds in borders, containers, lawns and paths, spoils the visual effect of the garden even when the growth of the garden plants is not affected. B
27
2.2 State what meant by an ephemeral weed, name 2 examples?
An ephemeral weed is a weed that has several life cycles in one year.
Cardamine hirsuta (hairy bitter cress)
Capsella bursa-pastoris (shepherd’s purse)
28
2.2 State what meant by an annual weed, name 2 examples?
An annual weed completes its life cycle in one growing season, so it germinates, grows, flowers, sets seed and dies all within one year.
Veronica persica (speedwell)
Poa annua (annual meadow grass)
29
2.2 State what meant by a perennial weed, name 2 examples?
Perennial weeds live for more than two years.
Aegopodium podagraria (ground elder) Ranunculus repens (creeping buttercup)
30
2.2 Name two weeds associated with recently cultivated soil.
In recently cultivated soil the seeds of ephemeral weeds such as *Cardamine hirsuta*, (hairy bitter cress) and Capsella bursa- pastoris (shepherd’s purse) which have been brought to the surface during digging, will germinate in large numbers.
31
2.2 Name two weeds associated with herbaceous perennial borders.
Perennial weeds such as Taraxacum officinale (dandelion) and Sonchus arvensis (sow thistle) and Aegopodium podagraria, grow alongside the garden plants. Growing very close to the plant, right under the leaves so that they are difficult to see.
32
2.2 Name two weeds associated with woody perennial plantings.
In woody perennial plantings, of shrubs and trees, perennial weeds range from the shorter species such as *Aegopodium podagraria* (ground elder) to the climbing species such as *Calystegia sepium* (hedge bindweed).
33
2.2 Name two weeds associated with lawns.
Two perennial weeds associated with lawns are *Ranunculus repens (*creeping buttercup) and *Bellis perennis* (*daisy).* They adapt well to living in lawns and form carpets or low rosettes so that they are not damaged too much by the mower blades.
34
2.3 What is a contact herbicide? Name one example and the active ingredient.
Contact herbicides are non–selective and work simply by killing off any plant material they come in contact with.
E.g. Weedol Gun! Fast Acting (RTU), active ingredient **acetic acid**
35
2.3 What is a translocated herbicide? Name one example and the active ingredient.
Translocated or Systemic herbicides enter the leaf, stem or roots and then move via the vascular system to reach all parts of the plant.
E.g. Roundup Fast Action (RTU), active ingredient, glyphosate
36
2.3 What is a selective herbicide? Name one example and the active ingredient.
Selective herbicides are hormone type weed killers that mimic plant hormones, causing twisted or distorted growth when applied to weeds. They are selective, targeting only broad-leaved weeds and leaving narrow-leaved plants like grasses (monocotyledons), unharmed at the normal dilution rate.
E.g LawnClear 2, active ingredient clopyralid/2,4-D/MCPA
37
2.3 Describe a situation where a contact herbicide can be used.
Contact herbicides can be used to control annual weeds on paths, waste ground or on prepared seed beds. They are non–selective and work simply by killing off any plant material they come in contact with.
38
2.3 Describe a situation where a translocated herbicide can be used.
Translocated or Systemic herbicides can be used to clear weeds prior to cultivation of a border or controlling deep-rooted perennials in an established border, as long as garden plants are protected. They enter the leaf, stem or roots and then move via the vascular system to reach all parts of the plant.
39
2.3 Describe a situation where a selective herbicide can be used.
**Selective herbicides** can be used on **lawns** **or rough grassland**. They are selective, targeting only broad-leaved weeds and leaving narrow-leaved plants like grasses (monocotyledons), unharmed at the normal dilution rate.
40
3.1 What is meant by the term ‘plant pest'?
A pest is a mammal, bird, insect, mite, mollusc or nematode that is damaging to plants.
41
3.1 Describe the damage done by rabbits.
Rabbits can consume half a kilogram of plant food a day.
* Young turf grasses and cereal crops are the worst affected, large areas may be destroyed in the seedling stage.
* Garden damage, bark on fruit and ornamental trees and shrubs. Vegetables, annual bedding plants, bulbs and herbaceous perennials.
42
# cultural, physical, biological and chemical
3.1 Describe methods of controlling rabbits.
**Physical** - brickwalls, wire mesh fencing buried 30cm underground at an outward angle. Plastic tree guards. Dogs or hunting with ferrets. Shooting by landowners.
**Cultural** - RHS list 150 plant species not attacked by rabbits. E.g. agapanthus, dahlia, snowdrop, clematis, berberis and weigela.
**Chemical** - Spraying aluminium ammonium sulphate on bedding displays, young trees and plants will act as a deterrent.
43
3.1 & 4 Describe the damage done by the cabbage white (large white) butterfly larvae. Describe at least **TWO** methods of minimising damage (including prevention)
Leaves of brassicas,*Tropaeolum majus* (nasturtium) etc are gradually eaten away. Skeleton leaves may result. Larvae and excrement on leaves.
**Physical** - Cover crops with fine netting. Pick off caterpillars.
**Cultura**l - Encourage birds, starlings will eat the larvae. Wash off eggs. Plant nasturtiums as an alternative host.
**Chemical** - Spray with insecticide containing pyrethrum.
44
3.1 & 4 Describe the damage done by the black bean aphid. Describe at least **TWO** methods of minimising damage (including prevention)
Most commonly damaged are broad beans but runner beans, french beans, peas and red beet are also susceptible. Aphids collect on soft new growth and flowers. Weakening sucking out the phloem. Aphids secret sugary liquid (honeydew) that can get infected by sooty mould. Plant growth is affected and seed production dramatically reduced.
**Cultural control -** remove soft tips of broad beans once the lower flowers have set.
**Biological control -** encourage natural predators and parasites such as ladybirds, lacewings and hoverflies.
**Chemical control -** organic insecticides such as pyrethrums and fatty acids.
45
3.1 & 4 Describe the damage done by the peach potato aphid. Describe at least **TWO** methods of minimising damage (including prevention)
Feeds on a wide variety of plants, including many flowers, fruits and vegetables. Usually found on youngest leaves and shoots, or on the underside of older leaves.
Sucking stylet - injects a digestive juice - distorts tissues - Secretes honeydew - blocks stomata - attracts sooty mould - slows photosynthesis/growth. Transfers viruses such as leaf roll virus, mosaic virus and leaf roll virus on potato.
**Physical control** - cover crop with fleece, pinching out infected growing tips when plant reaches maturity
**Biological control -** Outdoors natural predators such as ladybirds, lacewings, hoverflies, and parasitic fungi may reduce pest numbers. Greenhouse - small parasitic wasps such as Aphidus matricariae will give some control.
**Chemical control** - fatty acids, vegetable oils or pyrethrums is effective when sprayed onto the foliage from mid-spring.
46
3.1 & 3.4 Describe the damage done by the two spotted spider mite. Describe at least **TWO** methods of minimising damage (including prevention)
Attacks a wide range of plants inside (house & greenhouse) and outside during warm dry summers. E.g tomatoes, cucumbers, peaches, fuchsia, pelargonium, orchids. Host range is so wide few plants are immune.
Piercing and sucking mouthparts inject poison into leaf cells, causing localised death. Yellowish mottling of the leaf. Reduction in photosynthesis. Leaves lose green colour, dry up and drop off. Growth reduction and deterioration in fruit and flower production. Severe infestations you will see a build up of fine silk webbing.
**Cultural control** - check plants regularly for signs of attack. Greenhouses - Clear weeds in and around they act as hosts for the pest. Reduce overwintering mites to a minimum, clear out plant debris, old canes, stakes and plant-ties before the spring.
**Chemical control -** spray fatty acids or vegetable oils (several applications are necessary to break life cycle) Acetamprid can be used in glasshouses or for serious outdoor infections.
47
3.1 & 4 Describe the damage done by the glasshouse whitefly. Describe at least **TWO** methods of minimising damage (including prevention)
Causes serious problems on a range of glasshouse food and flower crops. Plants that are seriously attacked include fuchsias, cucumbers, chrysanthemums and pelargoniums. Tubular stylets enter the plant extracting sugary liquid from the phloem, causing large amounts of honey dew and sooty moulds to appear on the leaf surface. - New growth weakened with reduced flowering fruiting potential. Sooty mould blocks out light reducing photosynthesis and growth.
**Cultural control -** remove chickweed or sow-thistle as can harbour the pest. Regularly check underside leaves plants, for eggs or adults.
**Biological** – Encarsia formosa parasitic wasp
**Chemical –** Only effective against the young scales and adult stages. Pyrethrin and fatty acids.
48
3.1 & 4 Describe the damage done by the vine weevil. Describe at least **TWO** methods of minimising damage (including prevention)
Adult and larval(early autumn & spring) stages cause damage. Larvae live in the soil and feed on roots. Resulting slow growth followed by wilting and death when insufficient roots remain to sustain the plant. Larvae also bore into the tubers of plants such as cyclamen, and begonia. Slow moving adult beetles emerge at night and eat irregular notches from the leaf margins of many plants e.g rhododendrons, Euonymus japonicas, hydrangeas and bergenias. Containers are particularly at risk.
**Physical control** - Adults can be picked off indoor plants at night.
**Chemical control** - Larvae can be controlled by using a soil drench of acetamiprid. Only on ornamental plants growing in containers.
**Biological control -** Traps containing nematodes to control adults. Place traps below damaged plants, VW enter during the day and become infected with nematodes.
49
3.1 & 4 Describe the damage done by slugs. Describe at least **TWO** methods of minimising damage (including prevention)
Slugs move over and into the soil in search of food; young seedlings, roots, tubers and bulbs. Feeds with radula (cuts through plant material) and can scoop out cavities. Irregular holes are eaten in foliage, flowers and stems. Leave a slime trail. Most slugs live underground and do a lot of damage to potato tubers and tulip bulbs. Stay active until temp drop below +5.
**Physical** - removal at night, beer traps, placing coarse sand around the base of pots, copper strips
**Cultural control -** Encourage natural predators such as centipedes, ground beetles, glow-worm larvae, frogs, hedgehogs and song thrushes
50
3.1 & 4 Describe the damage done by the potato cyst eelworm. Describe at least **TWO** methods of minimising damage (including prevention)
Found in most soils where potatoes have been grown. Leaves plants become yellow and dry up from the bottom of the stems upwards. Plants become stunted and die during mid to late summer.
**Cultural control -** Crop rotation, growing potatoes in the same plot every fifth year will reduce the pest.
Use more resistant cultivars ‘Pentland Javelin’, ‘Maris Piper’ ‘Rocket’ and ‘Cara’.
Use certified seed potatoes.
Planting early cultivars of potatoes that are lifted before most nematodes have reached the cyst stage.
51
3.3 Describe 3 methods of pest feeding.
* **Biting** mouthparts (mammals, caterpillars, sawfly larvae and beetles)
* **Piercing/sucking** mouthparts (aphids)
* **Rasping** mouthparts (molluscs i.e slugs and snails)
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3.3 Describe how insects breathe.
Insects breathe through holes in their abdomen called spiracles which lead to an internal breathing system of tracheae.
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3.3 Describe 3 entry points for insecticides into insects.
**Mouth parts** - digestive systems take in poison to stomach.
**Spiracles** (breathing holes) - become blocked by the chemical pesticides containing plant oils.
**Cuticle** (waxy exoskeleton) - dissolved by chemicals containing fatty acids.
54
3.2 & 4 Describe the lifecycle of the cabbage white (large white) butterfly.
Two generations per year with caterpillars emerging from late spring until early autumn.
1. Eggs laid in batches 20–100 underside of cabbage leaves May/June.
2. Larvae hatch after 1–2 weeks; feed on leaves for about 5 weeks, then pupate.
3. Pupa attached by silk; 3–4 weeks hatches into adult butterfly in July/August.
4. Adult emerges in July/August. The pupae of this second generation overwinter.
55
3.2 & 4 Describe the lifecycle of the black bean aphid.
Eggs overwinter on woody host e.g. Euonymous europaeus or Vibernum opulus. 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. In autumn these live young include males and along with females they fly back to winter host to mate and lay eggs.
56
3.2 & 4 Describe the lifecycle of the glasshouse whitefly.
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 (crawlers) which then turn into scales. Last scale stage is thick walled and called a pupa, a new adult male or female fly emerges from this. Three days later the new female starts to lay eggs again. Cycle takes 32 days in spring and about 23 days in summer.
57
3.2 & 4 Describe the lifecycle of the vine weevil.
All adults are female, laying eggs, mainly in August and September in soil or compost next to the roots of a preferred plant species. Over a period of a few years one female may lay 1,000 eggs as she visits different plants. The larvae are white, legless, with a characteristic chestnut-brown head. They reach 1cm in length by December, when they pupate in the soil before developing into adult females and the cycle begins again.
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3.2 & 4 Describe the lifecycle of slugs.
Slugs are hermaphrodite. They mate in spring and summer and lay clusters of up to 50 round white eggs in rotting vegetation, the warmth of which protects the eggs during cold weather.
59
3.2 & 4 Describe the lifecycle of the potato cyst eelworm.
Eggs hatch in spring and larvae invade roots and suck up cell contents. Once larvae are fully developed they wriggle to outside of root. Female leaves head buried in root and swells. Males leave root and fertilise females. Females change colour and form cyst which then drops from the root into the soil where it can survive many years with eggs inside.
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4.1 What is meant by plant disease?
A plant disease may be defined as an unhealthy condition or damage to a plant caused by a fungus, bacterium or virus.
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4.1 & 4 Describe the damage caused by **grey mould** (fungus) Botrytis and method of spread.
2 methods of minimising the effects (or preventing
Grey mould will attack most plants, usually gaining entry via wounds or points of damage. Under humid conditions fuzzy grey mould grows on buds, leaves, flowers or fruit and the infected parts then turn brown and rot.
**Spread:** by spores, but also through soil and on plant remains.
* Strict hygiene, use clean disinfected equipment, dispose of infected materia
* Avoid damage to plants
* Minimising effects by reducing humidity and increasing ventilation; adequate spacing between plants
* No chemical controls available for amateur gardeners
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4.1 & 4 Describe the damage caused by **strawberry powdery mildew** and method of spread.
2 methods of minimising the effects (or preventing)
* First purple, yellow or reddish spots on the upper leaf surface which spread to the lower leaf surface
* Next fluffy white infection on upper leaf surface
* Leaf edges turn brown followed by early leaf drop
* Inability to photosynthesise leads to poor plant growth and fruit production.
* Flowers can be affected causing deep pink colouration
* Fruit distorted, dull in colour, seeds protruding. Covered in powdery white fungus
**Spread:** wind spread by means of summer spores. New planting material may also introduce the disease.
**Cultural control:** Remove weak plants in Autumn. Remove and destroy infected waste. Morning watering avoiding leaves and fruit. Grow resistant varieties ‘Pegasus’.
**Chemical control:** Potassium bicarbonate used as a spray by organic growers helps provide resistance to the disease in the leaf cells.
63
4.1 & 4 Describe the damage caused by **damping off** and method of spread.
2 methods of minimising the effects (or preventing)
Caused by any of the soil borne fungi, Pithium, Phytophthora, Rhizoctonia or Fusarium. Can affect most seedlings.
* seedlings fail to emerge as infection can occur below soil surface
* emerging seedlings infected at the soil surface causing collapse, often submerged in a mass of white fungal growth
* Occasionally the roots of mature plants can become infected, turning brown and soggy, causing plant death
**Spread:** Naturally occurring in soils. Under damp conditions asexual spores are produced that cause infection. Spores are spread by water.
**Cultural:** Grow seedlings in commercial growing compost, which is sterile. Use new or disinfected pots. Sow seedlings thinly. Do not over water.
64
4.1 & 4 Describe the damage caused by **honey fungus** and method of spread.
2 methods of minimising the effects (or preventing)
There are seven species of Armillaria in the UK. The most common species in gardens are: A. mellea and A. gallica.
**Above ground**
* **white fungal growth** can be seen between the bark and the wood at ground level
* Upper parts of the plant die. Sometimes suddenly during periods of hot dry weather, indicating failure of the root system; sometimes more gradually with branches dying back over several years
* Smaller, paler than average leaves
* Failure to flower or unusually heavy flowering followed by an unusually heavy crop of fruit (usually just before death)
* Premature autumn colour
* Cracking and bleeding of the bark at the base of the stem
**Below ground**
* Dead and decaying roots, with sheets of white fungus material (mycelium) between bark and wood, smelling strongly of mushrooms.
**Spread:** Underground by direct contact between the roots of infected and healthy plants and also by means of black, root-like structures called rhizomorphs. **An extremely destructive pathogen, can attack plants up to 30m (100ft) away from the source of infection.** Honey coloured toadstools may appear in autumn, these can be ignored as unimportant in the lifecycle.
**Cultural**: Excavate and destroy, by burning or landfill, all of the infected root and stump material.
Grow resistant plants E.g *Buxus sempervirens, Ginkgo biloba*
**Physical:** Dig a trench and place an impermeable barrier such as butyl rubber sheets to block rhizomorphs from spreading
**No chemicals available for control.**
65
4.1 & 4 Describe the damage caused by **rose black spot** and method of spread.
2 methods of minimising the effects (or preventing)
Common fungal disease in garden and greenhouse roses. Diplocarpon rosae
* Rapidly enlarging **black patch** appears on surface of the leaf
* **Leaves** turn yellow around spots and then drop off
* Sometimes leaves stay with lots of **small black spots**
* Small, black scabby **lesions** may appear on **young stems**
**Spread:** by water in (raindrops or irrigation)
**Cultural control:** Gather up all fallen leaves and burn or dispose of them in local authority bin.
Prune out all lesions in spring
**Chemical control:** systemic fungicide such as myclobutanil several times during the growing season will help to control the disease
66
4.1 & 4 Describe the damage caused by **potato blight** and method of spread.
2 methods of minimising the effects (or preventing)
Phytophthora infestans, disease of foliage and tubers of potatoes and foliage and fruit of tomatoes. Most common in wet weather or humid conditions.
**Spread:** sporangia (spore-bearing structures) blown on wind or rain splash landing leaves or stems. Spores need to swim in a film of water on the plant surface before they can penetrate the leaf tissues.
* brown patches on leaf tips and edges
* spots enlarge and leaves wither and die
* wet or humid conditions, fluffy white fungal growth on leaf underside, may be visible around spot edges too
* stems develop brownish-black patches and may collapse. Left unchecked, disease will pass to tubers
* tubers develop sunken, dark surface patches with reddish-brown discolouration beneath
* spreads to flesh turning into unpleasant-smelling slimy wet rot
* stem leaf symptoms similar on tomatoes, brown patches on green fruit, ripe fruit rot quickly
**Cultural control:** burn infected material or consign to green waste collection
operate crop rotation, at least 4 years
grow ‘sarpo’ range as offers resistance
**No chemical control.**
67
4.1 & 4 Describe the damage caused by **club roo**t and method of spread.
2 methods of minimising the effects (or preventing)
Plasmodiophora brassicae, affects Brassicaceae (Cruciferae) family including cabbage, cauliflowers and Brussel sprouts; ornamentals wall flowers, stocks and alyssum.
* pale foliage, chlorotic or pinkish in colour, wilts rapidly
* roots swollen and distorted, may show wet rot
* growth and yield severely reduced
**Spread:** soil- borne can remain viable in soil for in excess of 20 years. Introduced on infected plants, on boots, tools, imported growing media. Occurs in soils with high moisture content, high soil temperatures and a low pH.
Immediately burn infected material
Good weed control - *Capsella bursa-pastoris* (shepherd’s purse) *Cardamine hirsuta* (hairy bittercress) are susceptible
Plant brassicas in autumn when soil temperatures are lower
Select resistant cultivars e.g. summer cabbage ‘Kilaxy’, cauliflower ‘Clapton’, or Brussel sprouts ‘Crispus’
No chemical control
68
4.1 & 4 Describe the damage caused by **hollyhock rust** and method of spread.
2 methods of minimising the effects (or preventing)
Puccinia malvacearum, most common disease on hollyhocks, genus Althaea, in the UK. Especially damaging in wet summers.
* Bright yellow and orange **spots** develop on upper leaf surface
* Corresponding pin head sized raised orange **pustules** develop on lower leaf surface
* Spots may join together killing large areas of leaf tissue, causing it to shrivel and die
* Stems may have a **cankerous** appearance after infection.
* stunted growth reduced vigour
* Continued infection in wet summers often leads to stunted plants
**Spread:** pustules turn ash-grey under in high humidity, as airborne spores are produced. Spores create new infections when they land on other hollyhock leaves.
**Cultural control: Check** and remove infected plants. **Monitoring** bought in plants. Grow as a **biennial. Avoid** dense planting.
69
4.1 & 4 Describe the damage caused by **apple and pear canker** and method of spread.
2 methods of minimising the effects (or preventing)
Nectria galligena, Apples and pears are frequently affected; poplars (Populus), beeches (Fagus) willows (Salix) hawthorn (Crataegus) and sorbus may also succumb.
* Bark becomes discoloured, shrinking and cracking, forming concentric flaky rings
* Branches may become swollen around the cankered area. As the canker enlarges, the shoot may be girdled and so foliage and growth above it starts to die back.
* Younger branches may break off
* Stems and trunks may be attacked and very occasionally semi-mature fruit are infected and show rotting
* In summer raised white fungal pustules develop on the canker
* In winter raised red fruiting bodies develop
**Spread:** Spores spread on wind in entering leaf scars in autumn or through pruning wounds in winter
Prune out, remove and burn infected and damaged tissue. Disinfect all tools used.
Improve soil drainage. Apply lime as acid conditions encourage the disease.
70
4.1 & 4 Describe the damage caused by **fireblight** and method of spread.
2 methods of minimising the effects (or preventing)
Fireblight (*Erwinia amylovora)* is a bacterial disease that kills the shoots of apples, pears and related ornamentals, giving the plant the appearance of having been scorched by fire.
Damage seen from late spring until autumn. Bacteria overwinters in bark cankers. In warm, wet and windy weather in spring, bacteria ooze out of the cankers. Infections occur when the bacterium gains entry to the inner bark, usually via the blossoms
* Blossoms wilt and die at flowering time
* A slimy white liquid may exude from infections in wet weather
* Shoots shrivel and die as the infection spreads down the inner bark
* During the short period of active spread, the outer wood is stained a 'foxy' reddish-brown colour (similar to the colour of fox fur) when the infected bark is peeled back
* Cankers (areas of dead, sunken bark) on branches, especially where infected shoots join larger branches.
**Spread:** wind-blown rain and also by insects including bees.
**Control:** Prune out and burn infections, peel back bark to reveal the reddish-brown staining and cut back 30cm to healthy wood in smaller branches, 60cm in larger ones. Clean tools with disinfectant between cuts to avoid infection. Remove secondary, late blossoms before they open.
No chemical control.
71
4.1 & 4 Describe the damage caused by **bacteria canker on** ***Prunus*** and method of spread.
2 methods of minimising the effects (or preventing)
Bacterial canker is a disease of the stems and leaves of *Prunus*, especially plums and cherries, but also apricots, peaches and ornamental *Prunus* species.
* **On stems and spurs:** Sunken, dead areas of bark develop in spring and early summer, often accompanied by a gummy ooze. If the infection spreads all round the branch it will die rapidly.
* **On emerging shoots:** Shoots may either fail to emerge, or start to grow normally in spring before dying back rapidly. [](https://www.rhs.org.uk/disease/blossom-wilt)
* **On leaves:** Small brown spots appear, which are often round and eventually fall out to leave holes – as if the leaf had been hit by shotgun pellets, leading to the popular name of ‘shothole’
**Spread:** bacteria are **spread by rain**, overwintering on trunks, branches and leaves. In spring, entering the tree stomata or a wound.
**Control:** carry out all pruning in July or August when tissues are most resistant. Cut out all cankered areas, pruning back to healthy wood. Seal wounds with natural resin wound paint. Disinfect tools. Burn or or consign to green waste collection.
No chemical control.
72
4.1 & 4 Describe the damage caused by potato leaf curl virus**(and vector peach potato aphid)** and method of spread.
2 methods of minimising the effects (or preventing)
The main vector or carrier of this disease is the peach potato aphid Myzus persicae.
* leaves become thickened, showing an inward rolling caused by an accumulation of starch in the palisade cells.
* leaves become light green and may turn red on the upper side and purple on the lower side.
* leaves may make a rattling sound when shaken against each other.
* virus doesn't show any symptoms in the tubers but can cause a serious reduction in potato yield
**Spread:** Sap sucking insects such as aphids. Using infected material for propagation. Using contaminated tools such as knives, secateurs and saws for pruning.
**Cultural control:** - Use a resistant cultivar such as ‘Valor’ Don't use last year’s crop as seed potatoes. Buy potatoes certified as virus free. Remove any plants showing symptoms.
**Chemical control:** spray new foliage with an insecticide such as deltamethrin to prevent the plants being attacked by aphids.
73
4.1 & 4 Describe the damage caused by **tobacco mosaic virus** and method of spread.
2 methods of minimising the effects (or preventing)
Tobacco mosaic virus also called Tomato mosaic virus.
* Leaf symptoms include yellow mottling or mosaicing, distortion and unusually small leaves.
* Leaves may also curl downwards and the stem may show brown streaks in summer.
* Death of plant occurs when growing conditions are poor.
* Fruit yield is affected, green fruits yellow-bronze in colour and ripe fruit hard and inedible.
**Spread:** on fingers of gardeners
**Cultural Control:** heat treatment of dry seed at 70oC for four days by seed merchants helps to remove initial infections. Washing hands and tools in disinfectant. Growing resistant cultivars such as ‘Shirley’, ‘Estrella’ and ‘Cherry Wonder’ will reduce the chance of infection.
74
4.2 Outline the life-cycle of **damping off**.
* Pythium, Phytophthora and Rhizoctonia occur naturally in soils
* under damp conditions they produce the asexual spores that cause infection
* spores are spread by water
75
4.2 Outline the life-cycle of **clubroot.**
* Soil-borne organism remaining viable in excess of 20 years.
* Minute spores germinate to infecting root hairs
* The fungus forms a jelly-like mass (plasmodium) within the plant’s root system
* Plasmodium stimulates root cell division and causes cell enlargement, producing characteristic swollen roots
* When the swollen roots disintegrate they release many spores into the soil
76
4.2 Outline the life-cycle of **potato blight.**
* Microscopic, fungus-like organism whose sporangia (spore-bearing structures) are produced from leaf lesions.
* Sporangia are carried by rain splash or wind
* Infective spores need to swim in a film of water on the plant surface before they can penetrate the leaf tissues
* For infection to occur the fungus needs two consecutive 24 hour periods with a minimum temperature of 10oC (50oF) and relative humidity of 89% or more.
* When this occurs the fungus spreads rapidly through the crop.
* The fungus overwinters in rotten potatoes left in the ground or by the sides of fields.
* The great majority of infections in gardens arise from wind-blown sporangia originating in other gardens, allotments and commercial crops.
77
4.2 Outline the life-cycle of **honey fungus.**
* Fungus spreads underground by direct contact between the roots of infected and healthy plants
* Also spreading by black, root-like structures called rhizomorphs (often known to gardeners as ‘bootlaces’), which can spread from infected roots through soil
* Rhizomorphs are usually in the top 15cm but can go as deep as 45cm, at up to 1m per year.
* Very destructive pathogen, as can spread over large distances often attacking plants up to 30m away from infection source.
* Clumps of honey coloured toadstools sometimes appear briefly on infected stumps in autumn, but can be safely ignored as spores unimportant in the life cycle
78
4.2 Outline the life-cycle of **bacterial canker.**
* Most infections occur during wet windy weather in autumn or in damp conditions in spring.
* Bacteria are carried by wind-blown rain droplets, entering leaf scars and pruning wounds in autumn and young leaves in spring.
* Most wood infections occur through injured bark, such as that caused by pruning, frost crack or leaf fall.
* Infection during summer is rare.
79
4.2 Outline the life-cycle of **potato leaf curl virus.**
Peach potato aphid is the main vector
Aphids feed on infected potato plants taking up the virus at the same time as the sap
Virus multiplies in the aphid to such an extent that the it remains an active vector for the whole growing period of the crop
Aphids move from plant to plant and may also be blown considerable distances by the wind
High spring incidence of aphids usually results in increased levels of leaf roll virus in potato crops
80
4.4 Describe different methods of avoiding the spread of plant viruses.
Good hygiene - washing hands and disinfecting tools to prevent infection
Removing and destroying infected materials
Using resistant cultivars
81
5.1 What is a plant disorder?
A plant disorder is a condition in the plant resulting from a non-living factor.
* environmental factors - frost, drought, water-logging, incorrect soil pH or nutrient deficiency
* genetic disorder
82
5.1 How are plants and their growth affected by frost?
Frost causes **cells** to freeze, contents expand, cell **ruptures** and is killed. Plants blacken and die. Main damage occurs in non-hardy plants. However a hard frost in winter can damage hardy evergreens.
* **Scorched and damaged leaves**
* **Distorted buds**
* Damage to **young shoots and tips**
* Reduced production of **flowers and fruit**
* **Frost heave**: root system not established and lifted from soil
83
5.2 State methods of avoiding frost damage.
* Provide **protection** such as straw, fleece,cloches etc or bring tender plants under cover.
* **Avoid** planting in a frost **pocket**, take care planting against east-facing walls. Planting against a west- or south-facing wall will give some protection.
* Plant **selection** is important, choose hardier plants (use RHS plant hardiness ratings)
* Do not plant out **half-hardy plants** until all risk of frost is passed.
* Planting of **shelterbelts** can reduce damage from wind frosts.
84
5.1 How are plants and their growth affected by shade?
* Plants not adapted for growing in shade will have long internodes (part of a plant stem between two of the nodes from which leaves emerge) and will grow towards the light.
* Growth is often soft and pale and leaves are smaller.
* Do not flower well because plants require sugars to produce flowers and they cannot photosynthesise as effectively in low light levels.
85
5.2 State methods of avoiding shade damage.
* Check out the plants country of origin and natural habitat and always consider the soil and aspect when selecting plants for the garden.
* Choose only those plants that will grow well in areas of shade. Make sure it is right plant: right place!
86
5.1 How are plants and their growth affected by drought?
* Plants need sufficient water to function satisfactorily.
* Water participates directly in chemical reactions within the plant i.e. photosynthesis, and transportation of nutrients and food around the plant.
* Leaves change from shiny to dull and may also change from bright green to a grey-green.
* New leaves wilt, flowers may fade quickly and fall prematurely.
* Older leaves often turn brown, dry and fall off.
* Bolting when vegetable crops prematurely run to seed, usually making them unusable
87
5.2 State methods of avoiding drought damage.
* Cultivate the soil deeply, dig in large quantities of organic matter to improve soil structure, water retention and water availability for plants.
* Choose plants which suit the site’s soil type and aspect. Very dry soil choose plants with grey-green or silver leaves as they reflect the sun’s rays, helping to conserve moisture within the plant tissues.
* Mulching helps to retain moisture
* Irrigate plants regularly or at the critical points in their life such as fruit or flower development
88
5.1 How are plants and their growth affected by water-logging?
* Waterlogging occurs when the pore spaces in the soil become filled with water instead of air.
* Whole plant wilts and the lower leaves turn yellow.
* Growth may be stunted, stems and roots become brown, roots become black and rot.
* The presence of moss on lawns is a good indication of bad drainage.
89
5.2 State methods of avoiding water-logging.
* Improve soil structure and drainage through cultivation. introduce organic matter, sand and grit.
* If there is somewhere for water to go, drainage can be installed.
* Choose trees and plants that are well suited to wetter soils.
* When watering house plants make sure water can drain away so that plants are not left standing in water.
90
5.1 How are plants and their growth affected by high/low temperature damage?
* **High temps/sun:** cause water loss, and excessive sunshine can lead to scorched areas of leaves.
* Scorching of leaves, flowers and fruits is common and often seen as dry papery, buff or brown areas.
* Injury may be temporary or result in permanent tissue death
* leaf scorching is seen after watering in bright sunlight the cause may be due to the water droplets focusing sunlight on the leaves causing burnt areas.
* **Low temps:** Hardy plants and tough evergreens can be damaged by prolonged spells of severe cold when soil becomes frozen. Roots are unable to take up water and plants die from lack of moisture.
* **Snow:** As well as freezing damage, mechanical damage is caused by the weight of snow breaking branches.
91
5.2 State methods of avoiding high/low temperature damage.
**High temps**
* little can be done once injury has occurred
* Select plants suited to the growing conditions
* Avoid watering in bright sunlight (droplets focus light)
**Greenhouses** - further injury can be prevented by improving ventilation, provision of shading, damping–down of floor
**Low temps**
* Correct plant selection is essential
* Do not use fertilisers late in the season, as they stimulate sappy growth that is prone to chilling injury
* Plants can be protected from cold weather by wrapping horticultural fleece
92
5.1 How are plants and their growth affected by soil pH including the symptoms of lime induced chlorosis?
**Soil pH:** Most garden plants grow best at a pH of between 6 and 7 as most nutrients are available at that pH.
Some have a requirement or will tolerate more acid or alkaline soils. Outside their limits of tolerance plants may be unable to take up nutrients present in the soil so can suffer nutrient deficiencies.
**Symptoms** - leaf yellowing or browning, sometimes in distinctive patterns. Also may be accompanied by stunted growth and poor flowering or fruiting.
Non-calcifuge plants growing in acid soil can show calcium deficiency symptoms
**Lime induced chlorosis:** a common condition when a high pH can affect nutrient uptake and plant growth.
leaves show an unhealthy yellow appearance, especially between the veins of the leaves (interveinal chlorosis).
Young leaves are particularly affected in raspberries, rhododendrons, camellias and skimmias. A high pH limits the uptake of iron and magnesium.
93
5.2 State methods of avoiding damage by soil pH including the symptoms of lime induced chlorosis.
* growing only those plants that are suited to the pH of the soil
* grow ericaceous plants (dislike alkaline soils) plants in ericaceous compost in containers and watering with rain water in hard water areas
94
5.1 How are plants and their growth affected by fasciation?
* A condition where the stem grows abnormally because of a disturbance in the growing tip of the plant.
* Stems are wider and flatter than normal stem tissue and appear to be composed of several fused shoots
* Flattened elongated or misshapen flower heads are produced, with numerous flowers
* Commonly affected plants include delphiniums, euphorbias, forsythia, foxgloves, lilies, primulas and veronicastrum
* Fasciation is unpredictable and is usually limited to a single stem
* Fasciation seldom recurs on herbaceous plants the following year.
95
5.2 State methods of avoiding damage by fasciation.
* Affected parts of shrubs and trees can be pruned out if desired.
* Fasciation seldom recurs on herbaceous plants the following year.
96
5.1 How are plants and their growth affected by rose balling?
* **Outer petals** of rose bud die and become stiff so inner petals cannot emerge. **Buds go brown and drop off** or can become covered in **grey mould**. Buds feel soft and slimy.
* **Cool, wet weather** saturates the outer petals and then the **sunshine** dries and fuses them into a tight, papery shell, preventing the bud from opening.
* **Thin-petalled, double flowers** such as rose, peony and camellia cultivars are most susceptible to this condition.
97
5.2 State methods of avoiding rose balling.
* Remove balled buds promptly before grey mould sets in as it can infect other blooms or nearby plants and cause dieback of stems.
* Water plants in the evening, avoiding hot, sunny conditions, and always direct water at the base of plants rather than the foliage and flowers.
* Replacement of repeat offenders is sometimes the only remedy. Modern cultivars of roses are said to be less affected.
