Plant Health

Jump to each topic by clicking on the relevant box below

Define the term: abiotic

List abiotic factors in an environment

Define the term: biotic

List biotic factors in an environment

Each number relates to a specific word, so if you think (1)________ is 'bananas' then if (1)________ appears later on in the passage, 'bananas' is the missing word.

Abiotic factors:

All organisms have an optimum (1)________ at which cell processes function most efficiently. (2)________ (1)________ slows the rate of plant growth, limiting their ability to complete life processes. In spring, (3)________ (1)________, causing frost, can damage young growth. This can be especially damaging if (4)________ are affected in fruiting crops such as apple trees. Spring frost can reduce yields, reducing incomes for farmers and (5)________ for wildlife.
(6)________ is essential for healthy growth and in much of the UK is relatively abundant through most of the year due to consistent rain. However, due to (7)________ ________ prolonged dry spells are becoming more common, leading to (8)________ soil conditions. Plants that are not adapted for (8)________ soil will suffer a decline in health, exhibiting symptoms such as (9)________ leaves, slowed growth and leaf loss. Vegetable crops such as lettuce and spinach are more likely to (10)________, reducing yield.
Relative (11)________ is usually high in the UK. In autumn, high (11)________ combined with low air movement can lead to fungal diseases such as (12) b________ c________. This usually spreads from (13)________ to (14)________ parts of the plant and is especially prevalent in cool, damp weather. Low (11)________ increases the rate of (15)________, meaning plants remove more (6)________ from the soil, increasing its rate of drying. This is a problem in prolonged hot, dry weather which is becoming more common due to (7)________ ________.
The UK is a high (16)________ locality with most (16)________ coming from the south west. Strong (16)________ can (17)________ plants, such as snapping branches or blowing over taller herbaceous plants. (16)________ also lowers relative (11)________ around plants, (18)________ the rate of (15)________, which can lead to soil (8)________ more rapidly.
Plants require (19)________ for photosynthesis. The higher the (19)________ level the (20)________ the rate of photosynthesis, until another factor becomes limiting. This means the rate of photosynthesis, and therefore overall plant (21)________, is optimised when (19)________ levels are sufficient. However, some plants, such as many ferns, have evolved to grow in (22)________ and will experience (23)________ leaves if they're planted in full sun. Other plants, such as lavender and thyme, grow best in full sun.
Plants require (24)________ to produce new molecules and undertake healthy growth. Some (24)________, such as (25)________ are absorbed via the gas (25)________ (26)________ in plant leaves. Most (24)________ are absorbed as minerals via plant (27)________. If there are not sufficient minerals in the soil then plants will show signs of (28)________ in their leaves, slowed (21)________ and increased susceptibility to pests and pathogens.

Abiotic factors:

All organisms have an optimum (1) temperature at which cell processes function most efficiently. (2) Cool/cold (1) temperature slows the rate of plant growth, limiting their ability to complete life processes. In spring, (3) freezing (1) temperature, causing frost, can damage young growth. This can be especially damaging if (4) flowers are affected in fruiting crops such as apple trees. Spring frost can reduce yields, reducing incomes for farmers and (5) food/fodder for wildlife.
(6) Water/moisture is essential for healthy growth and in much of the UK is relatively abundant through most of the year due to consistent rain. However, due to (7) climate change prolonged dry spells are becoming more common, leading to (8) dry soil conditions. Plants that are not adapted for (8) dry soil will suffer a decline in health, exhibiting symptoms such as (9) wilting leaves, slowed growth and leaf loss. Vegetable crops such as lettuce and spinach are more likely to (10) bolt, reducing yield.
Relative (11) humidity is usually high in the UK. In autumn, high (11) humidity combined with low air movement can lead to fungal diseases such as (12) botrytis cinerea. This usually spreads from (13) dead to (14) living parts of the plant and is especially prevalent in cool, damp weather. Low (11) humidity increases the rate of (15) transpiration, meaning plants remove more (6) water/moisture from the soil, increasing its rate of drying. This is a problem in prolonged hot, dry weather which is becoming more common due to (7) climate change.
The UK is a high (16) wind locality with most (16) wind coming from the south west. Strong (16) wind can (17) damage plants, such as snapping branches or blowing over taller herbaceous plants. (16) wind also lowers relative (11) humidity around plants, (18) increasing the rate of (15) transpiration, which can lead to soil (8) drying more rapidly.
Plants require (19) light for photosynthesis. The higher the (19) light level the (20) higher the rate of photosynthesis, until another factor becomes limiting. This means the rate of photosynthesis, and therefore overall plant (21) growth, is optimised when (19) light levels are sufficient. However, some plants, such as many ferns, have evolved to grow in (22) shade and will experience (23) burned/scorched leaves if they're planted in full sun. Other plants, such as lavender and thyme, grow best in full sun.
Plants require (24) nutrients to produce new molecules and undertake healthy growth. Some (24) nutrients, such as (25) carbon are absorbed via the gas (25) carbon (26) dioxide in plant leaves. Most (24) nutrients are absorbed as minerals via plant (27) roots. If there are not sufficient minerals in the soil then plants will show signs of (28) chlorosis in their leaves, slowed (21) growth and increased susceptibility to pests and pathogens.

Hint: the missing words in a random order chlorosis, food/fodder, humidity, light, climate change, temperature, shade, wind, dry, cool/cold, nutrients, roots, water/moisture, Botrytis cinerea, higher, bolt, increasing, carbon, burned/scorched, transpiration, freezing, damage, growth, dead, wilting, dioxide, living

Extra Hint: (1) temperature

Extra Hint: (2) cool/cold

Extra Hint: (3) freezing

Extra Hint: (4) flowers

Extra Hint: (5) food/fodder

Extra Hint: (6) water/moisture

Extra Hint: (7) climate change

Extra Hint: (8) dry

Extra Hint: (9) wilting

Extra Hint: (10) bolt

Extra Hint: (11) humidity

Extra Hint: (12) botrytis cinerea

Extra Hint: (13) dead

Extra Hint: (14) living

Extra Hint: (15) transpiration

Extra Hint: (16) wind

Extra Hint: (17) damage

Extra Hint: (18) increasing

Extra Hint: (19) light

Extra Hint: (20) higher

Extra Hint: (21) growth

Extra Hint: (22) shade

Extra Hint: (23) burned/scorched

Extra Hint: (24) nutrients

Extra Hint: (25) carbon

Extra Hint: (26) dioxide

Extra Hint: (27) roots

Extra Hint: (28) chlorosis

For the following issues caused by abiotic factors, match the problem to solution by pairing the number and letters, for example you might think 1 matches to D

Wind damage to garden plants
A hydrangea shrub has wilted leaves during dry weather
Young cosmos plants planted in April are damaged by a late frost
A rose has chlorotic leaves and stunted growth
A Hosta plant develops dry, brown patches after a period of hot, sunny weather

A. Cover with horticultural fleece if frost threatens, or plant out later.

B. Plant a shelter belt hedge to buffer the prevailing winds.

C. Move to a shadier location in autumn.

D. Improve the soil's water holding capacity by mulching with organic matter. Irrigate with saved rainwater in extreme dryness.

E. Apply organic fertiliser to the soil to improve its nutrient content. Mulch with organic matter to improve nutrient retention in the longer term.

Click to reveal answers 1 - B 2 - D 3 - A 4 - E 5 - C

Note that nutrients are mentioned twice in the RHS theory syllabus:

- Unit 1, topic 2 (Plant Health), element 2 (Plant Nutrition and Plant Health)

- Unit 1, topic 3 (Plant Nutrition), element 2 (Role of Nutrients)

In the Unit 1 book nutrients are comprehensively covered in topic 3.2 (Nutrients) within topic 3 (Plant Nutrition), rather than being split across two topics. Their role in plant health is included in topic 3.2

Nutrients:

Split these into macro and micro nutrients:

What is a macronutrient?

What is a micronutrient?

Boron

Calcium

Carbon

Hydrogen

Iron

Magnesium

Manganese

Molybdenum

Nitrogen

Oxygen

Phosphorus

Potassium

Sulphur

Macronutrient

Micronutrient

Click to reveal Calcium Carbon Hydrogen Magnesium Nitrogen Oxygen Phosphorous Potassium Sulphur

Click to reveal Boron Iron Manganese Molybdenum

What is nutrient mobility?

Which nutrients are obtained from the air and water?

Split the nutrients listed above into mobile and immobile:

Mobile

Immobile

Click to reveal Carbon Hydrogen Magnesium Molybdenum Nitrogen Oxygen Phosphorous Potassium

Click to reveal Boron Calcium Iron Manganese Sulphur

In the RHS syllabus the role of nutrients in a plant is covered in topic 3 rather than here in topic 2. However, topic two details the symptoms and impacts of nutrient deficiencies:

(Again, note all content relating to nutrients is covered in topic 3.2 in the Unit 1 book)

State the deficiency symptoms of:

Boron Growing tips of roots and shoots become stunted with reduced vigour and eventual death. Brassica stems become hollow.

Calcium Leaf tips and margins curl downward, becoming chlorotic (yellowed). Root tips die back. Blossom end rot in tomatoes and peppers.

Iron Chlorosis of the younger leaves because iron is immobile and cannot be moved out of older leaves. Slow, stunted growth with eventual death of the plant.

Magnesium Interveinal chlorosis. Slow, stunted growth

Manganese Interveinal chlorosis with necrotic (dead) patches. Contorted new shoots and leaves

Molybdenum Pale, chlorotic leaves with scorched leaf edges

Nitrogen Chlorosis of older leaves, with older leaves eventually being shed. Slow, stunted growth.

Phosphorous Purpling of foliage, especially older leaves. Slow, stunted growth

Potassium Yellowing and browning of leaf margins and tips. Weakened stems and undersized fruits.

Sulphur Young leaves become chlorotic, older leaves remain green because sulphur cannot be translocated in the plant. (deficiency is rare as sulphur is an abundant nutrient.

Note: carbon, hydrogen and oxygen are never deficient.

Carbon is abundant via carbon dioxide. Hydrogen and oxygen from water are also abundant. If water is so lacking that hydrogen or oxygen deficiency would occur, the plant will already be dead.

Each number relates to a specific word, so if you think (1)________ is 'bananas' then if (1)________ appears later on in the passage, 'bananas' is the missing word.

Impacts of nutrients deficiencies on plants:

When nutrients are deficient plants growth will (1) ________ down and plants often become (2) ________. Deficiency of many nutrients results in (3) ________ of the leaves, which usually appears as a (4) ________ colour instead of healthy green. Not all nutrient deficiencies result in a (4) ________ colour, for example (5) ________ deficiency can result in a purpling of leaves. The site of (3) ________ depends on whether a nutrient is (6) ________. If a nutrient is (6) ________ then it can be moved from (7) ________ leaves to (8) ________ leaves. This results in (3) ________ of (7) ________ leaves. Some nutrients are (9) ________, in which case they cannot be moved to (8) ________ leaves. This means (7) ________ leaves remain a healthy green colour whilst (8) ________ leaves show signs of (3) ________.

Other symptoms of nutrient deficiency include undersized (10) ________, for example in strawberries or apples. Tomatoes and peppers can suffer from (11) ________ ________ ________ as a result of (12) ________ deficiency, making their (10) ________ unsuitable for harvest. A deficiency of (13) ________ in brassicas results in (14) ________ stems. Severe nutrient deficiency can result in the death of root and shoot (15) ________ ________.

Extreme nutrient deficiency will result in the (16) ________ of a plant. It's likely that it will suffer from (17) pe________ and (18) pa________ attack as a result of weakened growth, expediting its (16) ________.

Impacts of nutrients deficiencies on plants:

When nutrients are deficient plants growth will (1) slow down and plants often become (2) stunted. Deficiency of many nutrients results in (3) chlorosis of the leaves, which usually appears as a (4) yellow colour instead of healthy green. Not all nutrient deficiencies result in a (4) yellow colour, for example (5) phosphorous deficiency can result in a purpling of leaves. The site of (3) chlorosis depends on whether a nutrient is (6) mobile. If a nutrient is (6) mobile then it can be moved from (7) older leaves to (8) younger leaves. This results in (3) chlorosis of (7) older leaves. Some nutrients are (9) immobile, in which case they cannot be moved to (8) younger leaves. This means (7) older leaves remain a healthy green colour whilst (8) younger leaves show signs of (3) chlorosis.

Other symptoms of nutrient deficiency include undersized (10) fruit, for example in strawberries or apples. Tomatoes and peppers can suffer from (11) blossom end rot as a result of (12) calcium deficiency, making their (10) fruit unsuitable for harvest. A deficiency of (13) boron in brassicas results in (14) hollow stems. Severe nutrient deficiency can result in the death of root and shoot (15) growing tips.

Extreme nutrient deficiency will result in the (16) death of a plant. It's likely that it will suffer from (17) pest and (18) pathogen attack as a result of weakened growth, expediting its (16) death.

Hint: the missing words in a random order chlorosis, fruit, slow, older, blossom, death, younger, pathogen, phosphorous, stunted, mobile, hollow, calcium, pest, mobile, yellow, growing

Extra Hint: (1) slow

Extra Hint: (2) stunted

Extra Hint: (3) chlorosis

Extra Hint: (4) yellow

Extra Hint: (5) phosphorous

Extra Hint: (6) mobile

Extra Hint: (7) older

Extra Hint: (8) younger

Extra Hint: (9) immobile

Extra Hint: (10) fruit

Extra Hint: (11) blossom end rot

Extra Hint: (12) calcium

Extra Hint: (13) boron

Extra Hint: (14) hollow

Extra Hint: (15) growing tips

Extra Hint: (16) death

Extra Hint: (17) pest

Extra Hint: (18) pathogen

Match the word to the definition:

(answers will be given as the letter and number, e.g. if you think A matches 5 write A5)

A. Pathogen

B. Pest

C. Weed

D. Biological control

E. Chemical Control

F. Cultural control

G. Physical control

H. Pesticide

I. Herbicide

J. Selective herbicide

K. Insecticide

L. Fungicide

M. Algaecide

Click to reveal answers A 3 B 9 C 5 D 12 E 7 F 1 G 4 H 10 I 8 J 6 K 13 L 2 M 11

The management of plant collections to minimise likelihood of pests or pathogens affecting a plant in a detrimental way
A chemical that kills fungi
A microorganism that causes disease, commonly fungi, viruses and bacteria
Mechanical eradication or reduction of a pest
A plant growing in the wrong place, according to the gardener
Only kills a certain type of plant, e.g. kills eudicotyledon plants
The use of a chemical substance used to kill pests, including algaecides, fungicides, herbicides and insecticides
A chemical that kills plants
An organism that resides where it is not wanted. Conventionally this term is used to refer to animals where as 'weeds' is used for plants of this type
A synthetic product used to kill pests (including animals, pathogens and weeds)
A chemical that kills algae
The use of a living organism to predate or parasitise a pest
A chemical that kills insects

1. State the meaning of competition in a horticultural setting

2. What are the disadvantages of competition in a garden?

Larger neighbouring plants overshadow smaller plants, blocking light by taking up space above them. This reduces potential for photosynthesis in smaller plants, reducing their vigour. They will decline and eventually die
Plants compete for nutrients, reducing their abundance in the soil. This can lead to nutrient deficiencies, reduced vigour and yield of flowers/fruits/seeds in plants. Smaller plants with less extensive root systems will suffer more.
Plants compete for soil water. Plants with deeper root systems and adaptations to survive dry soil are better able to survive. Those less tolerant of dry soil can decline in health and may die out.
Weed plants can host pests or pathogens that can infect intended plants, for example rust spreading from Senecio vulgaris (common groundsel) to other garden plants

3. For each of the methods below, state one way of preventing or eradicating weeds:

- Cultural control

- Physical control

- Chemical control

- Cultural control:

Mulch the soil with 5cm of compost or bark chip to block light reaching the soil surface. This will prevent many weed seeds germinating as they require light as a germination trigger.
Ensure a dense planting scheme is maintained so young weed plants are outcompeted by established garden plants.

- Physical control

Remove weeds as seen by pulling out by hand, hoeing off or digging out of the soil.
Deadhead any weeds rather than letting them seed - this is a relatively quick prevention method, e.g. with Taraxicum officinale (dandelion), when there isn't enough time to remove the whole plant.

- Chemical control

Spray weeds with a herbicide, such as glyphosate (which will be banned in the UK by December 2025) or herbicidal vinegars to kill them.

Weeds and UK legislation.

Describe how each of the following UK legislations relate to gardens:

4. Evaluate your answers to Q3

(This means: give at least one advantage/positive and at least one disadvantage/negative for each)

- Cultural control:

Mulch the soil:

The advantages are that if produced in the garden via composting, this has very low carbon footprint. Mulching with organic matter also provides fodder to detritivores and decomposers, boosting soil biodiversity. These also improve the soil structure and texture by incorporating humus into the soil. Nutrient and water retention is improved, as is the aeration of soil. Disadvantages include the high carbon footprint if mulch is bought in, and the risk that viable weed seeds are in the mulch and will germinate at its surface.

Dense planting scheme:

The advantages are that dense planting fosters garden wildlife, improving potential for populations of natural predators, rare or endangered wildlife, and improving people's wellbeing through seeing/hearing more wildlife. Dense planting also reduces risk of soil erosion and plants support each other, reducing wind damage and need for staking. Dense planting can support a high plant biodiversity.
The disadvantages of dense planting is that it takes time to establish so newly planted areas need other control methods. It is not possible to achieve dense planting in spring in vegetable gardens where seeds are sown. Dense planting doesn't suit all design aesthetics, such as minimalist Mediterranean style gardens.

- Physical control

Remove weeds as seen by pulling out by hand, hoeing off or digging out of the soil.

The advantages are that this permanently removes the weed, preventing spread via seed, rhizome or root.
The disadvantages include a high time-input in physical removal and high skill required to identify established weeds vs. desired plants.

Deadhead any weeds rather than letting them seed.

The advantages include the quick removal of a future problem by reducing the locality's weed seed bank.
Disadvantages include the weed still being present and able to re-flower and seed, as well as (for some weeds) spread via rhizomes, stolons or roots.

- Chemical control

Spray weeds with a herbicide, such as glyphosate (which will be banned in the UK by December 2025) or herbicidal vinegars to kill them.

The advantage is the speed of control - spraying is much faster than physical removal.
The disadvantage is that weed killers are not specific to weed plants and can damage nearby intended plants. Professionals need a spraying licence and specialist equipment to spray safely, which is an additional expense.

(Note that the RHS does not recommend usage of any form of chemical weed killer - internet search 'rhs weedkiller' to access the RHS page detailing this)

5. What are the advantages of weeds in a garden?

Weeds can host natural predators such as ladybirds which consume aphids. Weeds left over winter provide overwintering habitat for natural predators.
Weeds provide fodder for garden wildlife, improving garden biodiversity.
Weeds themselves increase garden biodiversity by increasing the number of different species in a garden.
Weed roots bind soil which reduces soil erosion that occurs during heavy rain.
Weed leaves shade the soil, reducing soil heating and therefore surface evaporation of water. This reduces the rate at which soil drys out, important in reducing onset of drought in dry weather.
Weed leaves buffer the ground from rain drops falling directly on the soil surface. This reduces surface capping, which compacts the soil surface and reduces infiltration. Therefore weed coverage preserves better infiltration of water into the soil.

Weed Act, 1959 Plants listed in this act are considered invasive on agricultural land. It is illegal to let these grow on your property. Councils can fine property owners if plants on this list are found and not removed from their land.

Wildlife and Countryside Act, 1981 Schedule 9 of this act lists plants that are illegal to plant or allow to grow in the wild (e.g. via seed spread from a garden plant). It is not illegal to grow these in gardens.

Anti-social Behaviour, Crime and Policing Act, 2014 Reynoutria japonica (Japanese knotweed) is listed in this act. Although it's not illegal for it to be growing on private land, property owners can be issued with an antisocial behaviour order if they are deemed not to be sufficiently controlling its spread via underground rhizomes.

Name one weed included in each act:

Weed Act, 1959 - Cirsium arvense (creeping thistle) - Jacobaea vulgaris (ragwort) - Rumex obtusifolius (broad leaved dock)

Wildlife and Countryside Act, 1981 - Cotoneaster horizontalis - Lonicera japonica (Japanese honeysuckle) - Parthenocissus quinquefolia (Virginia creeper)

Anti-social Behaviour, Crime and Policing Act, 2014 Reynoutria japonica (Japanese knotweed)

Link the common weed plant to its lifecycle:

Ephemeral

Annual

Biennial

Perennial

Calystegia sepium (hedge bindweed)

Cardamine hirsuta (hairy bittercress)

Chenopodium album (fath en)

Myosotis sylvatica (forget-me-not)

Rubus fruticosus (blackberry)

Senecio vulgaris (groundsel)

Stellaria media (chickweed)

Taraxacum officinale (dandelion)

Urtica dioica (stinging nettle)

Click to reveal answers Ephemeral: Cardamine hirsuta Senecio vulgaris Annual: Chenopodium album Stellaria media Biennial: Myosotis sylvatica Perennial: Calystegia sepium Rubus fruticosus Taraxicum officinale Urtica dioica

How can all weed species potentially spread? Via seed. (Ephemerals, annuals and biennials only spread via seed)

State the various ways that perennials weeds can colonise new areas, giving one distinct example for each

Seed: perennials such as Taraxicum officinale flower and set seed. The seeds are wind blown to new areas, enabling colonisation

Rhizomes: perennials such as Calystegia sepium produce underground rhizomes that spread laterally in the soil. The rhizomes produce new roots and shoots, and can survive if severed. This enables it to colonise new areas.

Root suckers: Symphoricarpus albus (snowberry) is a shrub that produces new shoots from its roots, enabling it to colonise new areas

Bulbils: Allium paradoxum (few-flowered leek) produces bulbils, which are small bulbs, from the tips of its peduncle. At maturity these detach and scatter on the ground nearby, allowing it to colonise nearby areas.

Tip-layering: Rubus fruticosus (blackberry) produces long, arching stems that eventually bend over so their tips touch the ground. The stem tips root and produce new shoots. If severed from the main plant they survive, allowing the plant to colonise new areas.

What is a horticultural pest?

What is a generalist pest?

What is a pathogen?

What is a host-specific pest?

How can pests feed on plants?

Name the types of pathogenic organisms

State the main two ways plants naturally defend themselves from pests

Match the pest to its feeding mechanism:

A. Rabbit

B. Aphid

C. Slug

D. Vine weevil

E. Cabbage white butterfly caterpillars

F. Box tree caterpillar

Holes appear in leaves as a result of consumption by a rasping mouth piece.
Edges of leaves are eaten away, with all but the main leaf veins eventually being consumed.
Whole leaves and young stems are consumed.
Leaf contents between the upper and lower waxy cuticle are consumed, leaving a papery remnant of the leaf behind.
A piercing mouthpiece called a stylet is inserted into plant stems or leaves. Sap is consumed through the stylet.
Roots are consumed in their entirety, eventually removing the majority of the active roots of the plant.

Click to reveal answers A - 3 B - 5 C - 1 D - 6 E - 2 F - 4

Pest control methods should be followed in a particular order as part of best practice.

Order the following from first control consideration to last resort:

Chemical control

Physical control

Cultural control

Biological control

Click to reveal answers 1. Cultural control 2. Physical control 3. Biological control 4. Chemical control

How can a gardener utilise cultural controls to reduce mollusc (slug and snail) damage in a garden?

Avoid growing plants that are commonly eaten by some mollusc species, such as Hosta spp. or Delphinium spp.
Harden off newly acquired plants away from mollusc-prone areas. Many wholesale nurseries grow plants in polytunnels, especially in spring, to advance their growth. This results in faster but weaker, more mollusc-prone growth.
Prioritise growing hardy plants from seeds sown direct in the soil where possible. These produce more robust young plants that are less susceptible to mollusc damage. Alternatively, home grown seed sown plants should be fully hardened off before planting, and ideally grown to a larger size before planting. Larger, more established and fully hardened off plants are less susceptible to mollusc damage.

A tomato growing greenhouse suffered from a whitefly infestation last year. What can the grower do this year to prevent another infestation under organic and chemical-free growing principles?

First, undertake cultural control methods. The greenhouse should be thoroughly cleaned during winter with all surfaces scrubbed. A sterilant such as Jeyes fluid or soap and water can be used. All pots, tools and other horticultural equipment used in the greenhouse should also be cleaned. The greenhouse should be left open and allowed to experience freezing temperatures over winter. These will kill any surviving whitefly.

Tomatoes should ideally be grown from seed on site, eliminating biosecurity risk of potentially bringing affected material to site.

During the growing season yellow sticky traps should be hung amongst plants at leaf level. These should be monitored at least weekly. If whitefly are found, immediately order in the biocontrol Encarsia formosa and release into the greenhouse. This is a flying insect so the sticky traps need to be removed to prevent them capturing the biocontrol. Repeat order the biocontrol weekly, fortnightly or monthly if adult whitefly continue to be found. Check undersides of leaves for black scale-like infected nymphs vs. pale green healthy nymphs to check the biocontrol is working. This is a method of monitoring the biocontrol's efficacy and informs decision making for biocontrol ordering.

Describe a physical barrier to prevent rabbit damage on a young garden tree

Either:

Install a tree guard around the tree trunk to prevent rabbits gnawing the bark. The tree guard should be 60cm tall (above rabbit grazing height) and constructed of a strong, rigid material like plastic or rabbit-proof metal wire fencing.

Or:

Install a rabbit-proof fence around the garden to exclude rabbits. The fence should be at least 1.2m high to prevent rabbits jumping over it. The fence should also be buried 30cm into the soil to prevent rabbits digging a hole beneath it into the garden.

State chemical control options to treat aphids on ornamental plants in a greenhouse

Describe a biological control for two spotted mite affecting plants in a greenhouse

Release a predatory species such as Phytoseiulus persimilis which will consume the two spotted mite and reduce its population. This predator needs temperatures of at least 20°C and humidity of 60% or more, therefore it's only suitable during warmer months or in heated greenhouses. It may need re-releasing every two weeks or monthly depending on the severity of two spotted mite infestation. Releasing a large number on its first use will reduce the pest population more quickly.

The predator can be gently scattered onto plants from a bottle, or purchased in sachets that should be hung on affected plants.

What advice could you give to someone who has recently acquired an allotment and hopes to grow kale, cabbage and cauliflowers but is worried about caterpillars eating them?

Cabbage white butterflies lay eggs on brassicas such as kale, cabbage and cauliflower leaves. The eggs hatch into caterpillars that can quickly defoliate plants. The best way to prevent this happening is a physical barrier. A netted cage should be installed over the brassica growing area (brassicas should be grown together to make their protection easier), with netting holes no larger than 0.5cm square to prevent butterfly entry. Brassicas must be planted far enough from the netting to prevent leaves touching the net as butterflies can lay eggs on these. The netting should be pinned to the ground to prevent entry and the cage high enough for the tallest brassicas to reach maturity without touching the net. For kale this may be 1m high.

If caterpillars are spotted they can be handpicked off using gloves. If the yellow eggs are spotted they can be squashed by hand. Alternatively, a pathogenic nematode biocontrol (Steinernema carpcapse) can be sprayed over plants in cool, overcast weather. This may need repeating through the growing season.

Each number relates to a specific word, so if you think (1)________ is 'bananas' then if (1)________ appears later on in the passage, 'bananas' is the missing word.

Pest control strategies:

Many garden plants are susceptible to various pests so control considerations must be considered as part of a (1) g________ h________ p________. Within this there are (2)________ control methods that are best practiced in a particular order.

The first, (3)________ control, includes the selection of (4)________ cultivars, avoidance of plant species that are susceptible to a problematic pest, siting plants in suitable site (5) c________, and ensuring plants are spaced to maximise their health.
The next consideration is (6)________ control. This involves hand removal of pests, such as squashing (7)________ by hand if a small number are seen on the growing tips of e.g. young rooted cuttings in a greenhouse, or going out at night to hand remove (8)________ that are eating Hosta leaves. Hand removal is only practical on a (9)________ scale. Another (6)________ control method is to construct a barrier, such as a 1.8+m high garden (10)________ to prevent deer from entering the property.
In many cases it's not possible to prevent entry of a pest or manually remove them. Some pests, like (11) t________ s________ m________ affecting tomato plants in a greenhouse in late summer, are too small to be physically removed. Where possible, if (3)________ or (6)________ controls have not worked, (12)________ control needs to be considered next. These are most effective and often only used for (13)________, in which the (12)________ control will be contained. An example is the release of Aphidius colemani, a parasitic wasp of (7)________. This flying (14)________ ________ is generally contained with a (13)________ structure, meaning it only affects the pest population where it is a problem.
In the outdoor environment most pests have (14)________ ________ that consume them and can keep populations under a damaging threshold. (14)________ ________ can be encouraged by creating a (15) b________ garden with many overwintering and nesting sites, such as (16) l________ p________. However, some outdoor pests have been introduced from other countries and do not have (14)________ ________ in the UK. This includes (17) b________ m________ c________, which eats the leaves of Buxus sempervirens (common box). Some of these can be eliminated with a (12)________ control. For example, caterpillar pests can be controlled with a parasitic (18)________ which is watered or sprayed onto the caterpillars.
As a last resort, (19)________ control can be considered. These are usually sprayed onto plants and for professional use require a spraying (20)________. PPE must be worn to apply pesticides. Due to their danger to human health a (21) r________ a________ must be followed prior to using them. (19)________ controls are available as organic or inorganic products. When using any (19)________ control it should take place when there is no (22)________ to prevent spray-drift, and should take place at dusk when (23)________ are not flying.

Many garden plants are susceptible to various pests so control considerations must be considered as part of a (1) garden health plans. Within this there are (2) four control methods that are best practiced in a particular order.

The first, (3) cultural control, includes the selection of (4) resistant cultivars, avoidance of plant species that are susceptible to a problematic pest, siting plants in suitable site (5) conditions, and ensuring plants are spaced to maximise their health.
The next consideration is (6) physical control. This involves hand removal of pests, such as squashing (7) aphids by hand if a small number are seen on the growing tips of e.g. young rooted cuttings in a greenhouse, or going out at night to hand remove (8) molluscs (slugs/snails) that are eating Hosta leaves. Hand removal is only practical on a (9) small scale. Another (6) physical control method is to construct a barrier, such as a 1.8+m high garden (10) fence to prevent deer from entering the property.
In many cases it's not possible to prevent entry of a pest or manually remove them. Some pests, like (11) two spotted mite affecting tomato plants in a greenhouse in late summer, are too small to be physically removed. Where possible, if (3) cultural or (6) physical controls have not worked, (12) biological control needs to be considered next. These are most effective and often only used for (13) greenhouses, in which the (12) biological control will be contained. An example is the release of Aphidius colemani, a parasitic wasp of (7) aphids. This flying (14) natural predator is generally contained with a (13) greenhouse structure, meaning it only affects the pest population where it is a problem.
In the outdoor environment most pests have (14) natural predators that consume them and can keep populations under a damaging threshold. (14) natural predators can be encouraged by creating a (15) biodiverse garden with many overwintering and nesting sites, such as (16) log piles. However, some outdoor pests have been introduced from other countries and do not have (14) natural predators in the UK. This includes (17) box moth caterpillar, which eats the leaves of Buxus sempervirens (common box). Some of these can be eliminated with a (12) biological control, for example caterpillar pests can be controlled with a parasitic (18) nematode which is watered or sprayed onto the caterpillars.
As a last resort, (19) chemical control can be considered. These are usually sprayed onto plants and for professional use require a spraying (20) certificate. PPE must be worn to apply pesticides. Due to their danger to human health a (21) risk assessment must be followed prior to using them. (19) chemical controls are available as organic or inorganic products. When using any (19) chemical control it should take place when there is no (22) wind to prevent spray-drift, and should take place at dusk when (23) pollinators are not flying.

Hint: the missing words in a random order natural predators, resistant, physical, nematode, risk assessment, molluscs (slugs/snails), four, fence, greenhouse, log piles, garden health plan, two spotted mite, pollinators, chemical, aphids, cultural, certificate, wind, biological, small, biodiverse, box moth caterpillar, conditions

Extra Hint: (1) garden health plans

Extra Hint: (2) four

Extra Hint: (3) cultural

Extra Hint: (4) resistant

Extra Hint: (5) conditions

Extra Hint: (6) physical

Extra Hint: (7) aphids

Extra Hint: (8) molluscs (slugs/snails)

Extra Hint: (9) small

Extra Hint: (10) fence

Extra Hint: (11) two spotted mite

Extra Hint: (12) biological

Extra Hint: (13) greenhouse

Extra Hint: (14) natural predator

Extra Hint: (15) biodiverse

Extra Hint: (16) log piles

Extra Hint: (17) box moth caterpillar

Extra Hint: (18) nematode

Extra Hint: (19) chemical

Extra Hint: (20) certificate

Extra Hint: (21) risk assessment

Extra Hint: (22) wind

Extra Hint: (23) pollinators

1. Why can't diseases spread from one plant to another?

Diseases develop in a plant due to one major factor:

Presence of a pathogen (microorganism that causes disease)

Diseases cannot transmit between plants because disease is simply the symptoms of ill-health (with an underlying cause).

Pathogens (which cause disease) can move or be transferred between plants, causing disease to develop in new hosts.

Therefore pathogens spread between plants, and the presence of a pathogen causes disease in plants.

2. Name the three most common plant pathogens from most to least common

3. How does each of these pathogens spread?

Fungi:

Spreads by spores that travel in the air or in water
Spreads via (usually) underground mycelium strands

Viruses:

Spread by vectors including:

Though physical touch, e.g. animals (including human hands and tools) physically contacting plant surfaces and transferring virus particles from plant to plant
Sap-feeding insects such as aphids that move from plant to plant, transferring viruses via their feeding stylet

Bacteria:

Spread by wind, water (e.g. rain splash), or physical touch (as for viruses, above).

Match each pathogen to the descriptive points:

(Some descriptive points match to more than one pathogen)

A. Virus

B. Fungi

C. Bacteria

Single celled
Some species are multi-cellular
Not living
All are pathogenic (but each is specific to its host species only and harmless to other organisms)
Some are pathogenic but most are not
Produce mushrooms as fruiting bodies
Cannot be seen without a powerful microscope
Some form symbiotic relationships with plant roots, obtaining nutrients for plants in exchange for sugars
Are replicated by a living host cell
Some species are decomposers
Can be killed with fungicides
Some species fix nitrogen in the root nodules of legumes

Click to reveal answers A: 3, 4, 7, 9 B: 2, 5, 6, 8, 10, 11 C: 1, 5, 7, 10, 12

Match each disease to one of each of the following categories:

E.g. A - 3 - 5 - 8, B - 3 - 4 - 6 (these example answers are partially or fully incorrect)

A. Powdery mildew

B. Rust

C. Rose blackspot

D. Cucumber Mosaic Virus (CMV)

E. Bacterial canker

F. Potato blight

G. Grey mould (botrytis)

Pathogen:

1. Bacteria

2. Fungus

3. Virus

Host:

4. Generalist

5. Host specific

Click to reveal answers A - 2 - 4 - 7 B - 2 - 4 - 11 C - 2 - 5 - 9 D - 3 - 4 - 6 E - 1 - 5 - 8 F - 2 - 5 - 12 G - 2 - 4 - 10

Symptoms:

6. Affects a wide range of plants (the name is misleading). Yellow patches on leaves in random patterns, with heavily affected leaves curling downward. Plant growth becomes stunted with reduced flower and fruit production. Flowers can have white streaks in the petals, fruit are reduced in size and misshapen.

7. White patches appear on leaf surfaces, often during dry summer weather. Older leaves are affected first, with the infection spreading quickly across leaf surfaces and to younger leaves.

8. Affects deciduous Prunus species such as cherries, plums, damsons. Dark, sunken areas on branches ooze a gummy substance. The sunken areas spread around stems, eventually girdling them. Leaves may have a 'shotgun' appearance where small holes cover the leaf.

9. Very dark spots appear on leaves. They grow rapidly in size and eventually the whole leaf is shed. Symptoms appear on nearby leaves. Plants can become severely defoliated and lose vigour.

10. Common in autumn, coinciding with cool, damp weather when humidity is very high and there is a lot of dead, damp vegetation around (which this pathogen also lives on). Soft plant tissues develop a fuzzy, grey-ish surface. Leaves, flowers and fruits can be affected, with the symptoms eventually killing affected areas.

11. Orange-red pustules develop on leaf surfaces, usually on the undersides of leaves. Heavily affected leaves may fall prematurely, reducing plant vigour.

12. Occurs in summer during hot, humid weather with warm nights. Brown spots appear on leaves with a yellow/light green leading edge. They very rapidly spread across leaves and into stems and can kill plants relatively quickly.

1. What three control methods are used in horticulture against pathogens?

2. In what order should these be utilised as part of best practice?

3. Give one way each of the control methods named in Q1 could be used in a named horticultural situation

Cultural control:

Avoid growing susceptible plants, e.g. do not grow deciduous Prunus such as cherry 'Morello' or plum 'Victoria' where bacterial canker is problematic nearby.
Grow resistant cultivars, e.g. leek 'Porbella' is resistant to leek rust.
Space plants to prevent spread of pathogens, e.g. do not plant roses in close proximity to prevent rain splash of rose black spot, e.g. from Rosa 'Charles Darwin' to nearby plants.

Physical control:

Remove infected leaves of courgette 'Defender' as soon as powdery mildew is seen to reduce spread to unaffected leaves.
Space out or thin strawberry 'Albion' fruits in autumn to reduce incidence of grey mould/botrytis and pick fruits as soon as ripe to reduce risk of infection

Chemical control:

Rose blackspot, e.g. on Rosa 'Charles Darwin', can be treated with a fungicide

What does PPP stand for? Plant Protection Products Regulations 2012

Where must the use of PPPs be minimised? - Public areas - Surfaces that drain directly into water courses, mains drainage, sewage systems - Conservation areas - Healthcare facilities - Areas used by agricultural workers

Why are PPP's regulated? PPP's relate to the use of pesticides in the UK. Pesticides can be harmful to people and the environment, therefore their availability and use is regulated by UK legislation.

Each number relates to a specific word, so if you think (1)________ is 'bananas' then if (1)________ appears later on in the passage, 'bananas' is the missing word.

PPP's relate to the use of (1)________ in the UK. These regulations were launched in (2)________ and updated in (3)________. Key foci of the legislation includes:

Users of professional products require a (4)________ such as a PA6 for spraying (1)________.
Users of PPP's must take reasonable precautions to protect the (5)________ and (6)________ health.
PPP's must be confined to a (7)________ area.
PPP's must not be (8)________ unless the label state's it's suitable to do so.
PPP's must be (9) s________, h________ and d________ of in a way that does not endanger the (5)________ or (6)________ health.
Users of PPP's must take precautions to protect (10)________ environments, such as a (11)________ zone around water bodies.
In (3)________ a supplement to the PPP regulations was introduced requiring importers, manufacturers, distributers and sellers of PPP's in Great Britain to (12)________ with the relevant competent authority. Additionally, where PPP's are used in a professional capacity, inspections will be made by the (13) h________ and s________ e________.

PPP's relate to the use of (1) pesticides in the UK. These regulations were launched in (2) 2012 and updated in (3) 2020. Key foci of the legislation includes:

Users of professional products require (4) certification such as a PA6 for spraying (1) pesticides.
Users of PPP's must take reasonable precautions to protect the (5) environment and (6) human health.
PPP's must be confined to a (7) target area.
PPP's must not be (8) mixed unless the label state's it's suitable to do so.
PPP's must be (9) stored, handled and disposed of in a way that does not endanger the (5) environment or (6) human health.
Users of PPP's must take precautions to protect (10) aquatic environments, such as a (11) buffer zone around water bodies.
In (3) 2020 a supplement to the PPP regulations was introduced requiring importers, manufacturers, distributers and sellers of PPP's in Great Britain to (12) register with the relevant competent authority. Additionally, where PPP's are used in a professional capacity, inspections will be made by the (13) health and safety executive.

Hint: the missing words in a random order mixed; 2012; environment; aquatic; target; stored, handled and disposed; pesticides; certification; buffer; human; register; health and safety executive; 2020

Extra Hint: (1) pesticides

Extra Hint: (2) 2012

Extra Hint: (3) 2020

Extra Hint: (4) certification

Extra Hint: (5) environment

Extra Hint: (6) human

Extra Hint: (7) target

Extra Hint: (8) mixed

Extra Hint: (9) stored, handled, disposed

Extra Hint: (10) aquatic

Extra Hint: (11) buffer

Extra Hint: (12) register

Extra Hint: (13) health and safety executive

Q1. Which five pieces of the information below (1 - 10) must appear on a UK plant passport?

Q2. Write them down in the order A - E they would appear on a plant passport

Common name
Country of origin
Botanical name
Phytosanitary number
UK
Registration number
Transit countries
GB(NI)
Date of entry into UK
Traceability code

Q1 Click to reveal answers Five pieces of information: 2. Country of origin 3. Botanical name 6. Registration number 8. GB(NI) 10. Traceability code

Q2 Click to reveal answers Five pieces of information: A. Botanical name B. Registration number C. Traceability code D. Country of origin E. GB(NI)

Where do UK plant passports apply? They are issued to plants that move within the UK

Why are plant passports important? They ensure that plants are traceable. This is important, for example, if a new pest is found on an imported plant. The plant passport details will help locate other plants in that shipment to trace the localities the new pest could have been introduced into. This can help prevent new invasive species becoming established.

Apart from containerised plants, what else require plant passports? - Bare root plants - Seed potatoes - Some seeds - Wood - Some wood products - Isolated bark - Christmas trees >3m tall or branches taken from Christmas trees >3m tall

Who must keep a record of plant passport information? Professionals and organisations must keep plant passport records for 3 years.

In what circumstances can a plant be moved without a plant passport? When a plant is moved 10 miles or less between premises owned or rented by the same organisation or individual

In what circumstances would a plant require a phytosanitary certificate? All plants entering the UK require a phytosanitary certificate. Plants propagated and distributed within the UK only require a plant passport.

What is biosecurity?

What are notifiable pests and diseases?

How can biosecurity be maximised in a garden?

Biosecurity can be maximised by:

Minimise the introduction of new plant material into a garden other than growing from seed within a garden.
Purchase plants locally, ideally from nurseries who propagate their own stock rather than ordering in stock from far away.
Inspect plants at the nursery before purchase for signs of pests or disease.
Do not buy plants that show signs of pests or disease.
Only buy plants that are propagated and grown within the UK (i.e. not imported from abroad)
Quarantine all new plants for at least three weeks, inspecting them regularly for pests or disease.
Keep records of all new plant introductions, including plant passport and vendor details
Avoid importing topsoil into gardens.
Aim to compost all organic matter within a garden and avoid importing mulch material.

If a notifiable pest or disease is suspected, who should be contacted?

How does plant health relate to resilience to pests and pathogens? A healthy plant has greater resilience to pests and pathogens. Plants with sufficient water, light and nutrition produce more sugars due to a higher rate of photosynthesis. This is essential to fuelling plant defence mechanisms.

What are garden health plans? They are a holistic approach to consider factors that maximise plant health. They consider biotic and abiotic factors, and IPM.

What is IPM? IPM stands for Integrated Pest Management. It involves: - Crop walks to inspect plants and monitor plant health - Identification of pests, pathogens, disorders or other plant health issues - Establishment of damage thresholds and ongoing monitoring - Establishing control options - Implementing controls using the following, in this order of preference: cultural, physical, biological, chemical

State the main concepts of garden health plans, giving at least one detail for each concept

Garden health plans integrate the following key concepts:

Right plant, right place: only select plants that are suitable to the site conditions.
Maintain optimum site conditions: e.g. mulch soil to improve its health, plant a shelter belt hedge to reduce wind damage, apply organic fertiliser to prevent nutrient deficiency in vegetable plants, maximise biodiversity to increase the population of natural predators, ensure trees are planted with their root flare at soil level and keep mulch from burying the trunk, etc.
Manage competition: ensure weeds (spontaneous plants) are removed when seedlings or regularly remove perennial weeds as they emerge from the soil. Maintain desired plants' size to prevent them becoming overcrowded and smaller plants being outcompeted.
Maintain strict biosecurity: avoid introducing new plants other than from seed or propagation within the garden; only obtain plants grown locally and inspect them to check for pests or disease at the nursery; quarantine new plants for three weeks, checking them regularly for pests and diseases.
Practice integrated pest management (IPM): regular crop walks to check for pests or disease; swift identification of any found, at which point a management programme should be followed that establishes damage thresholds and mitigative action that focuses on (in order): cultural control, physical control, biocontrol, chemical control.

Which of the following statements would be suitable as part of a garden health plan, taking into account other issues such as sustainability?

Prevent pests by applying pesticides weekly through the growing season
Change soil texture through the addition of grit to improve drainage in a border where hardy succulent plants will be grown
Assess site conditions such as soil type and microclimates and only grow plants suited to these conditions
Plant a shelter belt to reduce windspeed across a garden with the aim of reducing wind-damage to garden plants
Install a reusable cage and netting on a brassica bed prior to planting with the aim of preventing entry of cabbage white butterflies
Spray glyphosphate herbicide to kill ephemeral weeds growing in the cracks of a brick pathway
Set automatic irrigation to turn on for several hours each night across the garden during hot, dry weather
Install bug hotels, log piles, leaf piles and other features that create overwintering habitat for natural predators
Lift and divide perennials to prevent them becoming too large and crowding each other out
The main criteria in selecting a new plant for a flower border is the colour and shape of its flowers

Click to reveal answers The following are suitable and unsuitable for sustainable garden health plans: 1. No: pesticides are a last resort 2. No: grit has a high transport carbon footprint. The amount needed to significantly change soil texture is not a sustainable option 3. Suitable 4. Suitable 5. Suitable (important that the materials will be reused for many years) 6. No: weedkillers are a last resort. Weeds can be scrubbed from a brick path with a wire brush 7. No: garden plants suitable for the site do not need irrigation in dry weather unless they are recent (within the last year or two) plantings. New plants should be spot watered to reduce water wastage. 8. Suitable 9. Suitable 10. No: first and foremost the plants must be suitable for the site conditions, and varieties resistant to potential pests or pathogens. Flower shape and colour are a later consideration when selecting potential new plants.

Why can't I find references to garden health plans on the internet or in books? (other than relating to the RHS level 2 syllabus) Garden health plans were introduced as a holistic concept to maintain plant health in the (new) 2022 RHS level 2 syllabus. It pulls together various aspects of best horticultural practice, such as 'right plant, right place' and IPM, that is already being implemented in many gardens. The term 'garden health plan' simply formalises a range of practices into a broad concept that can be applied in any horticultural situation to maximise plant health.