The following directory
contains descriptions of common garden pests and
diseases. it is divided into pests and diseases
that can occur in spring,summer,autumn or winter
Spring pests and diseases
BLACK SPOT –
Roses, particularly those which require heavy pruning
– for instance, modern roses – are prone
to this fungal disease, which appears as black spots
on the leaves. Regular fortnightly sprays of triforine
or propicanizole from March to October will protect
FLIES – These pests are not confined
to vegetables; they will also attack stocks and
wallflowers. The tiny white maggots eat the roots,
causing leaves to wilt and turn a bluish colour.
Before planting, dust the holes with a soil insecticide
or, if plants are already in, apply it to the
immediately around the plants before mid-spring.
CHAFER GRUBS –
Bulbs, tubers and fleshy roots are attacked by
these 1 ½ in long, brown-headed, white
grubs. Use HCH powder or bromophos dust raked
into the soil around the plants.
the larvae, called leather jackets, of the crane
fly, popularly named daddy-long-legs, eat roots
and the base of stems of many plants. They are
2in long, grey-brown, plump and tough-skinned.
Keep them in check by dusting the soil with HCH.
Many members of the rosaceous family, such as
cotoneaster and pyracantha, are prone to this
disease. Leaves and flowers die and turn dark
brown, as though scorched. As it is very infectious,
affected plants must be destroyed and the local
Ministry of Agriculture office notified.
FLEA BEETLES –
When the leaves of plants such as wallflowers,
stocks and alyssum become pitted with small holes,
these striped beetles, about ?in long, are the
likely culprits. Keep them at bay by dusting plants
with derris powder or HCH at an early stage of
The white froth commonly known as cuckoo spit
covers the immature froghoppers while they feed
on young growth. Apply a strong water jet from
a hand sprayer to dislodge them, but if they persist,
spray with malathion or fenitrothion.
GREY MOULD –
If stems and flowers go mouldy, especially in
damp weather, they could have this disease, also
known as botrytis. Apply a systematic fungicide,
repeating as necessary.
LEAF MINERS –
The grubs of this pest will tunnel inside the
leaves of chrysanthemums, rhododendrons and lilacs,
leaving unsightly white tracks. Spray with hexyl,
HCH or malathion.
SCAB – Pyracantha
and crab apples are attacked by scab, which shows
as brown spots on leaves and rough lesions on
twigs. Spray from early spring onwards with a
SILVER LEAF –
This fungal infection gives the leaves of trees
a silvery sheen, and they will split and turn
brown. Affected branches turn brown and die back.
Cut them out completely and burn them.
SLUGS AND SNAILS
– Perhaps the most common of garden pests,
these gastrapods cause great damage to flowers
and foliage. There are slug pellets that are non-injurious
to other wildlife and liquid slug killers on the
market. Alternatively you can trap them in jars
of beer sunk to their rims in the soil.
These aptly named creatures – they look
like pieces of wire and are almost as tough –
damage the roots of most flowering plants, particularly
carnations and chrysanthemums. They can be controlled
by dusting the soil with HCH, but perhaps the
best and most natural way is to dig over the soil
and expose them for birds to eat.
These grey, flat, oval-bodied creatures may feed
on stems, leaves and roots, but rarely do real
damage. Regular cultivation and keeping the garden
clear of plant debris will get rid of them as
they hate disturbance and light.
WOOLY APHIDS –
Cotoneaster, pyracantha and ornamental crab apples
are among the shrubs and trees at risk from these
aphids, easily recognised by their white woolly
tufts. They puncture stems and suck the sap, and
also damage the bark which splits and later becomes
infected with diseases such as canker. Get rid
of the insects by painting the colonies with methylated
Summer pests and diseases
Among the many pests that bother the gardener
during the summer months are ants which build
nests in garden soil and around plant roots. Get
rid of them with a proprietary ant killer.
CAGGAGE WHITE CATERPILLARS
– The leaves of nasturtiums, wallflowers,
stocks and ornamental brassicas are eaten by this
green, brown or grey caterpillar. The caterpillars
and egg-clusters can be picked off by hand; alternatively,
spray with permethrin and dimethoate or dust with
derris powder, paying particular attention to
the undersides of leaves.
CAPSID BUGS –
These tiny creatures are ¼ in long and
may be green, brown or yellow. They attack herbaceous
plants, leaving ragged holes and distorted tissue
in young growth, and punctured buds, so that when
the flowers open they are malformed. Spray with
a systematic insecticide or malathion in spring
if these pests attack regularly. Spraying after
the damage is done is too late.
CLEMATIS DIE-BACK –
The cause of this disease, commonly called clematis
wilt, when whole plants wilt and die for no apparent
reason, is imperfectly understood. If it occurs,
cut the plant back to ground level and water with
a systematic fungicide. Initial planting of the
clematis several inches deeper than normal allows
for the development of healthy shoots beneath
the surface as replacements.
Plants that topple over because the stems have
been eaten at soil level may have been attacked
by cutworms. They are flat, soft, greeny-brown
caterpillars with dark marks on each side of their
2in long bodies. Regular hoeing will expose the
creatures to frosts and birds, and keeping weeds
down are preventative measures; HCH dust or bromophos
can be raked into the soil around established
plants that are infested.
DOWNY MILDEW –
There are several types of downy mildew, which
is most prevalent in wet periods. Different types
attack different plants, but can generally be
identified by a grey mould on the undersurfaces
of leaves. This can be controlled by spraying
with mancozeb or copper fungicide. Systematic
fungicides are of little use against downy mildews.
These familiar pests, with their glossy brown
bodies and pincers at the tail, damage many young
leaves and flowers. HCH dust or hexyl will get
rid of them, or they can be enticed into upturned
pots of straw placed on top of stakes and trapped.
Remove and burn the infested straw every few days.
There are two species of this sap-sucking insect
to watch out for, the pale yellow rose leafhopper
and the green, red-striped rhododendron leafhopper.
The insects feed on the undersurfaces of leaves,
causing white flecks or mottling on the surface.
Both species can be controlled by treating the
plant with malathion, HCH or derris.
LEAF SPOT –
Disfiguring, brown, round fungal blotches appear
on leaves affected by leaf spot, and as they spread
invade plant tissues and destroy the cells. If
not controlled quickly, leaves will shrivel and
plants may die. Spray with a systematic fungicide
or Bordeaux mixture.
LUPIN APHIDS –
These pests that appear on lupin stems are like
large greenfly, but are covered with a wax coat
which makes control difficult. The best way to
get rid of them is to dislodge them with a strong
jet of water or spray with heptenophos.
POWDERY MILDEW –
The fungus appears as a powdery coating on the
stems and leaves of many plants during hot weather.
Spray with systematic fungicide.
RED SPIDER MITES
– You may need a powerful hand lens to detect
these tiny creatures on the underside of foliage,
but their presence is indicated by the discoloration
of leaves, which drop off prematurely. Treat them
with malathion or douse the plants daily with
RUSTS – many
types of plants are affected, especially roses,
hollyhocks, hypericums, pelargoniums and sweet
Williams. Orange-red pustules which eventually
turn black appear on the undersides of leaves,
and yellow spots appear on the upper surfaces.
Infected leaves should be removed and burned.
Treat with propicanizole or copper fungicide.
When rose leaves roll up tightly, spray them immediately
with a systematic insecticide and burn infested
leaves, for this is a sure sign that the larvae
of the sawfly are feeding in them.
SOOTY MOULD –
Sap-sucking insects such as aphids and whiteflies
excrete sticky honeydew which encourages the growth
of this blackish fungus. Eliminate the problem
by using methods described under aphids and whiteflies.
It is the larvae of these minute brown or black
insects, sometimes called thunder flies, that
attack gladioli, roses and carnations and cause
silver streaking on leaves and flowers. Use a
systematic insecticide against them, and treat
gladioli corms with HCH dust while they are in
– This fungal disease requires drastic action.
Callistephus, perennial asters and dianthus, as
well as some rhus, cotinus and acers may look
as if they are short of water, which gives the
disease its other name of sleepy disease, but
they will never recover. Dig up the infected plants
and destroy them, and do not put the same or any
related plants in that piece of ground for several
years, as the spores can survive in the soil.
The adult whitefly is a tiny, moth-like insect
commonly found in greenhouses, but also known
to infest outdoor plants such as rhododendrons,
honeysuckles and viburnums. The young insects
feed on sap and foul the leaves with a sticky
excretion called honeydew, which encourages sooty
mould. Control is difficult, but spraying with
permethrin-based insecticides or malathion will
WHITE RUST –
Chrysanthemums may be hit by this fungal disease,
which appears as round, yellowish-white pustules
on the undersides of the leaves, and eventually
causes premature death of the foliage. Spraying
with propicanizole will prevent the disease occurring,
but if it appears, destroy all affected plants.
Autumn trouble spots
As winter approaches, protect trees and shrubs,
especially those newly planted, against strong
winds with a windbreak material attached to strong
stakes. Protect tender plants against frost with
small-mesh plastic net, Hessian, straw or bracken.
A mulch of peat, pulverised bark or garden compost
will protect roots and tubers below ground.
Heavy soil which remains wet for long periods
can be detrimental to plant growth, so improve
drainage before any planting is done. One answer
is to add large amounts of gritty sand and organic
matter to open up the soil.
There are still some pests and diseases to watch
out for, especially when digging – this
is the best time too for removing and burning
CLUB ROOT –
Once this disease is in the ground it is difficult
to clear. Identified by irregular swellings on
the roots of wallflowers, stocks and related plants,
it should not occur if you buy healthy plants.
The disease is most common on wet, poorly drained
soil, so improving the drainage can help. Dip
the plants’ roots in a systematic fungicide
solution at planting time.
HONEY FUNGUS –
identified by yellowish-brown toadstools or strands
like boot laces in the soil around the base of
a tree or shrub, this fungus can attack any plant
and is very damaging. Affected plants should be
lifted and burned, but get the diagnosis confirmed
by an expert before destroying valuable trees
and shrubs. The ground must be sterilised with
an agent such as dephenolated creosote or the
soil replaced before growing anything on the site
STEM AND BULB EELWORMS
– Herbaceous perennials and the bulbs of
tulips, scillas and narcissi are attacked by these
minute, wormlike creatures which are invisible
to the naked eye. Infested bulbs feel soft around
the neck and the foliage is stunted and sometimes
splits. Always buy firm, dry bulbs. Destroy affected
bulbs and plants, though root cuttings taken from
perennials such as phloxes will be healthy. Do
not, however, put any susceptible plants in infected
ground for several years.
SWIFT MOTH CATERPILLARS
– These 1-2in long caterpillars live underground
and feed on fleshy roots and bulbs they are often
found when herbaceous borders are dug in the autumn.
Dust the soil with HCH or bromophos and suppress
weeds to make the border less attractive to egg-laying
Winter trouble spots
Keep the garden tidy during winter. Decaying plant
material will harbour pests such as slugs and
woodlice, and contribute to the spread of diseases.
Many pests are dormant at this time. It makes
better use of your horticultural chemicals to
wait and see what pests appear in spring than
to spray indiscriminately with a toxic cocktail
at the egg stage, that would wipe out beneficial
Heavy snowfall on evergreens can cause them to
become misshapen and their branches to break under
the weight, so dislodge it as soon as possible.
CORAL SPOT –
This fungal disease appears on dead or dying twigs
of trees and shrubs as tiny, salmon-pink spots.
It can move down into living wood causing die-back,
and will attack acers, beeches, cercis and magnolias.
Remove and burn the infected wood.
DAMPING OFF –
This may affect seedlings which have recently
germinated or have been overwintered, particularly
if they were sown in unsterilised compost. Always
sow in sterile compost and water all seed trays
with Cheshunt compound or copper fungicide after
sowing and again just as seedlings appear.
Badly pruned, insect or frost-damaged branches
on roses and other woody plants may develop die-back.
Remove and destroy the affected parts and treat
the cut areas with a systematic fungicide.
MICE – Young
shoots, seeds and seedlings in a cold frame or
greenhouse, and bulbs in the garden, are a favourite
diet of mice. Lay traps or keep a cat.
PEACH LEAF CURL
– Ornamental prunus are attacked by this
disease. When the buds burst the young leaves
distort and eventually turn red, then thicken
and later brown and drop off. To protect your
plants, spray with Bordeaux mixture or copper
fungicide during early February, and again in
autumn. Collect and burn the leaves as they fall.
friendly pest control
Chemical pest control