Transcript Level 2 Unit 205 - College of Agriculture, Food and Rural

 Pests
and Diseases in
Horticulture
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Level II Agricultural Business Operations
Session 10
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Acknowledge information and pictures from www.hdc.org.uk website
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Top Fruit Diseases
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Apple Scab
Apple Canker
Powdery Mildew
Crown Rot
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Top Fruit Pests
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Red Spider Mite
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Aphids e.g. Green fly, woolly Aphid
Caterpillars e.g. Codling Moth, Blastobasis
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Soft fruit Diseases
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Phytophthora
Botrytis(Grey Mould)
Powdery Mildew
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Horticulture pests
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Vine Weevil
Leather Jackets
Carrot Fly
Slugs
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Acknowledge information and pictures from above website
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Fungus overwinters within the tissues of
infected leaves and ascospores develop in
early spring.
Scab also overwinters on bud scales so
infecting young leaves as they emerge in
spring
Another source of infection is lesions within
the wood which have resulted from
infections the previous year
Temp
(C)
Temperature
(F)
From
Primary
Inoculum
Apr-Jun
(Ascospore)
Hours of
leaf wetness
From
Secondary
Inoculum
May-Oct
(Condia)
Hours of leaf
wetness
Days
required for
lesions to
appear
9
48
15
10
17
10
50
14
9
16
11
52
12
8
15
13
55
11
7
14
14
57
10
6.5
13
16-24
61-75
9
6
10
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Routine control of apple scab through fungicide
application during the spring and summer period is
essential for business success in commercial apple
production.
The optimum interval between fungicide
application, and thus the total number of fungicide
applications during the production cycle depends
on prevailing weather conditions, and the
associated incidence of Apple Scab Infection
Periods (ASIPs).
In Northern Ireland, the incidence of ASIPs is
assessed using meteorological data from AfBI,
Loughgall.
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Apple canker is an economically important disease of apple
The fungus attacks twigs and branches, causing cankers and dieback in
mature trees, and often death of young trees.
It also attacks fruit causing rots both in the orchard and in store.
Losses due to canker are difficult to estimate, but those of 10% or more in
young trees in newly planted orchards are typical and, in seasons favourable
to the disease, losses due to rots in stored fruit can be as high as 30%.
The fungus is not specific to apple and attacks pear and quince and several
forest and hedgerow trees including beech (Fagus), poplar (Populus),
hawthorn (Crataegus) and Acer.
These other susceptible species could therefore act as a source of Nectria
inoculum. In practice only poplar has been implicated in canker outbreaks in
apple orchards.
The disease is present in virtually all the apple producing areas of the world
Its prevalence as canker or fruit rot is dependent on seasonal rainfall
patterns.
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Control
Spring Summer spray programme
Autumn spray programme (Copper Spray at
5% and 50% leaf fall)
Remove prunings from the orchard
Cut out/prune out cankers from the tree
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Powdery mildew is an important disease of apple.
All the main UK culinary and dessert varieties are
susceptible, especially Cox and Jonagold.
The fungus overwinters as mycelium in fruit buds
or vegetative buds which emerge as primary
mildew i.e. mildewed blossoms at pink bud or
mildewed shoot tips at petal fall.
During spring and summer mildew spreads from
the primary mildew sources to developing shoots
(secondary mildew epidemic) and under
favourable conditions can infect leaves and
produce sporing mildew colonies in about
4-5 days.
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Primary blossom mildew
Mildew colonises fruit buds in early summer
(about June) and colonises vegetative buds at the
end of extension growth in late summer, where it
remains quiescent until the following spring.
Symptoms are readily recognised on shoot tips,
leaves, blossoms and fruit.
Mildew inoculum level is the key factor in
determining the seasonal epidemic. Managing
the mildew epidemic through careful watching of
disease incidence is essential to rationalise
fungicide use and to check that control measures
are effective.
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Crown rot and collar rot are distinct diseases.
Collar rot is a disease of the scion which usually only attacks mature
trees >10 years old.
Crown rot a disease of the rootstock which, in the UK, is mainly a
disease of young trees in the first two years of establishment.
Susceptibility of varieties and rootstocks varies, with Cox, James Grieve,
rootstock MM.106 being the most susceptible.
Both diseases are caused mainly by Phytophthora cactorum and are
favoured by wet weather. P. cactorum is soil borne and can overwinter
and survive in the absence of apple as oospores (resting spores). These
germinate to release zoospores which move in soil moisture to infect the
roots/root crown or scion through cracks, damage or lenticels.
The first symptoms of crown or collar rot may be poor growth, leaf
yellowing or premature autumn colours.
In the rootstock below ground the presence of typical orange/red-brown
rot under the bark is characteristic of crown rot.
A water-soaked, weeping area on the trunk which has a distinct
orange/red-brown rot under the bark is characteristic of collar rot.
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Fruit tree red spider mite has a simple life cycle, overwintering as eggs
on the bark, mainly around fruiting spurs. Eggs hatch in late April to mid
June, around blossom time of apple. Young mites then invade the leaves
and trusses.
There are five or six successive generations of adults, mainly on the
undersides of leaves, before eggs are laid on bark in the autumn. The
generation time is about 4 weeks with 3 moults.
The pest is seldom a problem in orchards where the orchard predatory
mite Typhlodorums pyri is established and encouraged. It is important
to regularly monitor levels of the pest and the predator.
The presence of high populations of fruit tree red spider mite which
causes bronzing of foliage (yellowing leaves with brown speckles) and
fruit russeting is an indication of failure of proper integrated mite
management. The predatory mite should be introduced, by transferring
summer prunings in summer to newly planted orchards and to orchards
where it is absent.
Pesticides harmful to the orchard predatory mite should not be used
except as a last resort, as they cause outbreaks of rust and spider mites.
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Apple- Grass Aphid
Green apple aphid
Rosy apple aphid
Rosy Leaf-Curling Aphid
Woolly Aphid
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Symptoms
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The Larva leaves a prominent, red-ringed entry hole in the side of the apple blocked
with dry frass.
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Description
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Adult 20mm wingspan. Forewings are grey with coppery coloured tips. 5 pairs of prolegs
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Life Cycle
First generation adult moth flies in June/July. Mating occurs at dusk when temp >14
degrees. Eggs are laid singly on fruitlets. No. of eggs laid increases with temperature.
They hatch10-14 days later and the larvae enters the apple where it feeds for 14-18
days passing through five instars. The larvae leaves the fruit and spins a cocoon to
overwinter under loose bark then pupates in the late spring. In hot summers, cocoons
may pupate in late July producing a second generation in Aug/Sept.
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Assessment
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Pheromone traps attract males. Threshold is 5 moths/trap/week in 2 out of 4 weeks
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Control
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Apply insecticide10-14 days after threshold catch to coincide with the onset of egg
hatch
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Symptoms
Bramley and short stalked varieties susceptible. Damage on fruit as deep surface grazing and
internal mining. Fruits in clusters are most prone to attack, damage occurring where adjacent
fruit touch. A sticky mass of black frass is produced.
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Description
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Adult is straw coloured with 20mm wingspan and each wing having 4 darker spots.
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Life Cycle
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Adults emerge from June and lay eggs on leaf and flower debris. Larvae emerge 7 days later
and feed extensively beneath dead leaves around the stalk of maturing fruit.
Pupation occurs in Sept in small cocoons amongst debris where the insect overwinters on the
ground.
Assessment
No pheromone traps are available at present. Low levels of damage at harvest should prompt
treatment the next year.
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Prevention
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Regular use of broad spectrum pesticides as soon as caterpillars or damage are seen.
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Caterpillars are the larval stage of various
butterflies and moths. There are several species of
caterpillar that feed on brassicas leaving holes in
the leaves and hearts of cabbage, other brassicas
and other plants including turnip, swede,
horseradish and nasturtiums.
Large cabbage white butterfly caterpillars are
yellow and black with obvious hairs on their
bodies.
Small cabbage white butterfly caterpillars are pale
green and covered in short, velvet-like hairs.
Cabbage moth caterpillars are yellowish green or
brownish green, with no obvious hairs on their
bodies.
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Vine weevil is a beetle that attacks a wide range of plants, both indoors
and outdoors, but especially plants grown in containers.
It is one of the most common and devastating garden pests. The adult
weevils eat plant leaves during spring and summer, but it is the grubs
that cause the most damage over autumn and winter when they feed on
plant roots, causing wilting, and often plant death.
Plants growing in pots or other containers, outdoors or under cover, can
be severely damaged by vine weevil grubs. Plants growing in the open
ground are less susceptible, although the grubs can kill strawberries,
primulas, polyanthus, Sedum, Heuchera and young yew plants.
The adult beetles feed on the foliage of many herbaceous plants and
shrubs, especially Rhododendron, evergreen Euonymus, Hydrangea,
Epimedium, Bergenia, Primula and strawberry.
Symptoms – The larvae feed on the roots of plants so the first indication
of anything wrong could be the collapse and death of the plant. Adult
vine weevil will feed on the leaf of many different plant species.
Larva (grub) – soil living
Adult Weevil – above ground
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Slugs and snails will eat most parts of vegetables and
herbaceous plants, with the young growth in spring
particularly vulnerable. Slugs will also eat seeds and tubers,
and maincrop potatoes are often badly damaged. They are
most active at night and in humid conditions.
Symptoms – Irregular holes in leaves and other parts of the
plant. Slime trails can be seen on soil and hard surfaces.
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Soil borne Phytophthora Diseases
Affected plants do not thrive, and later wilt. Red Core is
caused by the fungus Phytophthora fragariae. When the
main roots are cut longitudinally the stele is a
distinctive dark red/brown.
Crown rot is caused by Phytophthora cactorum. Affected
crowns have distinctive markings when cut in half.
Both these diseases can come in contaminated runners
so runners should either be drenched before planting or
sprayed with a fungicide after planting.
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Powdery Mildew
Powdery mildew is the most serious disease of table top strawberries
under cover. A preventative fungicide programme is most important.
Mildew is exacerbated by high humidity, so is usually more severe
towards the end of the season. Tunnels with poor drainage or over
watering, and which have standing water on the ground are the
worst affected. Infection is mainly from spores which overwinter in
the tunnel. If mildew is well controlled in Autumn, fewer spores
overwinter to cause trouble in the new season.
Development and spread of powdery mildew is temperature
dependent. Infection can start slowly in cool spring weather and may
be seen by carefully observing leaf roll, or checking with a hand lens
on the under surface of leaves for early mycelium. If not treated at
this stage it can rapidly become severe as temperatures rise.
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Control in soft fruit
Protectant sprays applied 7-10 day intervals early in the
season or when humidity and risk are low, or every 7 days in
the season or when humidity is high. Good coverage,
especially of underside of leaf where infection enters.
Sulphur is an economical way to control mildew. Resistance
does not develop to sulphur in the way that it does to
synthetic fungicides. It can be applied as a spray or by
sulphur burners. Such burners are most suited for use under
glass. A drawback is that they weaken polythene, so use
should be restricted in polytunnels. Flowable Sulphur is more
convenient to use than wettable powder.
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Most infection is at flowering, with the fungus lying
latent for a period. Increased humidity and sugar
availability makes the latent infection active. When
it appears in the ripening fruit, direct infection to
new fruit then occurs. The disease overwinters on
dead material around the crown. One function of
the late winter clean up of the old plant material is
to reduce the carry over of Botrytis
Fungicides include Systhane, Topas, Signum,
Amistar, Fortress, Corbel, Kindred, Potassium
bicarbonate.
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Aim for a water volume of 1,000l/ha to give good
coverage of table tops.
A fine spray is most effective. Check nozzles.
Impurities in water make chemicals less effective.
Rain water (filtered) gives the best results. Mains
water is usually preferable to bore hole water for
spraying. The latter tends to have more dissolved
salts and is sometimes contaminated with bacteria.
Note: Always read the product label. Use pesticides
safely. If applying a product under an EAMU
(Extension of Authorisation for Minor Use) you
should be familiar with the terms of use and keep a
printed copy of same for your records.
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Leatherjackets are the larvae of crane flies.
They are soil inhabiting pests that mainly
feed on roots and the underground parts of
stems of crops.
Biggest population in a field going into crop
from grass
Life cycle is eggs hatch in Aug/Sept with the
larvae feeding until May. Larvae pupate near
soil surface in May with adults emerging in
Jun/July. Adults do no direct damage.
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Carrot fly is widespread pest of carrots with
the larvae feeding on roots of carrot. The
larvae can kill young plants and leave larger
plants unmarketable. The fly does not travel
far.
First generation carrot flies emerge in Apr
with eggs laid in May. Larvae feed and pupae
are formed during Jun/July. Adults emerge
from July onwards to produce overwintering
generation which continue to feed on
overwintered crops.
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Non chemical control
Crop rotation
Time of sowing
Mesh covering
Monitoring with yellow sticky traps