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Diseases in Avocado

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					REVIEW OF COMMON DISEASES IN
AVOCADO, PINEAPPLE & CITRUS
DISEASES IN AVOCADO
Bacterial diseases
• Blast and bacterial fruit spot : Pseudomonas syringae
                                  Xanthomonas campestris

• Crown gall               : Agrobacterium tumefaciens

• Bacterial canker          :    Pseudomonas syringae
    Fungal diseases
• Anthracnose           : Colletotrichum gloeosporioides
                          Glomerella cingulata [teleomorph]Armillaria
   root rot

• Shoestring root rot   : Armillaria mellea
                          Rhizomorpha subcorticalis [anamorph]

• Black mildew           : Asteridiella perseae
                           Irene perseae

• Branch canker         : Botryosphaeria disrupta
                          Botryosphaeria obtusa

• Butt rot    : Ganoderma zonatum
                Ganoderma sulcatum

• Cercospora spot (blotch) : Pseudocercospora purpurea

• Clitocybe root rot    : Armillaria tabescens
                          Clitocybe tabescens
•   Collar rot :Sclerotinia sclerotiorum
•   Dematophora root rot : Dematophora necatrix
                          Rosellinia necatrix [teleomorph]
•   Dieback     : Diplodia cacaoicola
                 Phomopsis sp.

•   Fruit rot (includes stem end rot & fruit spots) : Botryosphaeria obtusa
                                                   Botryosphaeria quercuum

•   Heart rot     : Oxyporus latemarginatus
                    Poria latemarginata

•   Leaf spot        : Bipolaris sorokiniana
                       Cochliobolus sativus [teleomorph]
                       Pestalotia spp.
                       Pestalotia adusta

•   Phomopsis spot        : Phomopsis spp.

•   Physalospora canker : Physalospora perseae
•
•   Root rot              : Pythium spp.

•   Rosellinia root rot     : Rosellinia bunodes

•   Phytophthora root rot    : Phytophthora cinnamomi
Viruslike diseases
•   SunblotchAvocado : sunblotch viroid

•   Trunk pitting     : Graft transmissible agent


Miscellaneous diseases and disorders
•   Algal spot      : Cephaleuros virescens Kunze

•   Blackstreak     : Unknown cause

•   Dieback         : Copper deficiency

•   Edema           : Physiological

•   Littleleaf rosette :Zinc deficiency

•   TipburnExcess :mineral salts
Anthracnose
(Colletotrichum gloeosporioides
Glomerella cingulata [teleomorph]Armillaria
root rot
Symptoms
•   Anthracnose symptoms can develop on flowers, fruit, leaves, or twigs

•   Infected fruit is the most serious concern, but most fruit damage does
    not develop
     until after harvest

•   Unhealthy or dead leaves are the most obvious symptom in groves.

•    Spots form on leaves, beginning as yellow, then brown discolorations
    that coalesce into large dead areas. Necrosis occurs across or
    between leaf veins, on leaf margins, and most often at leaf tips. If
    disease is severe, trees drop many leaves prematurely.

•   New shoots can develop brown or purplish lesions, and shoots may
    dieback

•   Infected flower heads can turn dark and die without producing fruit, or
    young fruit may form and then drop.

•   After harvest, lesions become blacker, larger, and increasingly
    sunken. Lesions eventually spread over the entire fruit surface and
    throughout pulp. When the fruit is cut in half through one of the
    lesions, rot extending into the flesh often exhibits a hemispherical
    pattern.
Management
•   Good cultural practices in the grove and proper preharvest and
    postharvest fruit handling.

•   Prune out dead limbs and twigs where fungi sporulate. If many dead
    leaves are entwined in the canopy, knock them out of the tree.

•   Prune low limbs to at least 2 feet (60 cm) off the ground to reduce
    humidity within canopies by improving air circulation.

•   Keep fruit dry and cool until sold.

•   Postharvest temperature is especially critical to anthracnose
    development. Cool fruit to 41°F as soon as possible after harvest.
    Delays of longer than 6 hours before cooling and higher pulp (air)
    temperatures during these delays will result in increased postharvest
    fruit decay.

•   Chemical Control:
    Anthracnose is rarely significant enough in California avocado groves
    to warrant fungicide application. Copper compounds thoroughly
    sprayed on healthy tissue can prevent infection
Avocado Black Streak
   (Unknown cause)
Symptoms
•   Black streak appears as an elongated dark discoloration on bark.

•   Small cankers can develop in a direction that parallels the direction of limb
    or trunk growth but sometimes cankers encircle limbs or the trunk.

•   On green shoots and young trees, lesions look like black blotches with
    distinct margins.

•   Cankered bark develops shallow cracks that ooze sap, which dries as a
    brownish or white powder on the bark surface.

•   Black streak lesions can be very small or encompass the greater part of the
    trunk. Cankers often first appear on the lower trunk and the underside of
    lower limbs and then later appear higher in the tree. Scraping off bark over
    the canker reveals shallow reddish brown to black areas.

•   This discoloring forms mottled areas of dead and live tissue or merges into
    one large necrotic area. It rarely extends into the wood and can be removed
    easily by inserting a knife blade under the canker and prying upwards.
    Because trees can die with very few lesions, the lesions appear to be a
    symptom of the disease and not the cause of tree death.
Management
• Maintaining plant health with good fertilizer and irrigation
  practices, and preventing stress.

• Adequate irrigation with high quality water is believed to
  be especially important.
Avocado Root Rot (Phytophthora
Root Rot)
Phytophthora cinnamomi
Symptoms
• Foliar symptoms of avocado root rot include small, pale green or
  yellowish leaves.

• Leaves often wilt and have brown, necrotic tips.

• There may be little leaf litter under infected trees.

• Small branches die back in the tree top, exposing other branches
  and fruit to sunburn because of the lack of shading foliage.

•    Fruit production declines, but diseased trees frequently set a heavy
    crop of small fruit.

• Small, fibrous feeder roots are scarce at advanced stages of this
  disease. Where present, small roots are black, brittle, and dead from
  infection.
Management
•   Cultural Controls
    Use cultural practices that promote growth of the tree while discouraging
    growth of the pathogen.

•   Provide favorable soil conditions
•   Plant on well-drained soil, or improve drainage by planting on a soil berm,
    deep-ripping impervious subsoils, or installing subsurface drains.

•   ] Use certified disease-free nursery stock.
     Request certified, disease-free plants, especially when planting new areas,
    because disease is especially damaging to young trees.

•   Plant resistant rootstocks. Certain rootstock cultivars are more tolerant of
    root rot, including Dusa, Latas, and others.
•   Prevent soil or water movement from infested areas.

•   Soil solarization

•   Establish a barrier. Establish the barrier around healthy sections of the
    grove, at least two tree rows beyond where tests indicate the fungus is
    present.
•   Irrigate carefully:Appropriate irrigation is the single most critical practice
    for improving tree health and managing root rot.

•   Use high-quality irrigation water:Irrigation water with high overall salinity
    or an excess of boron, chloride, or sodium promotes infection of roots by
    Phytophthora.

•   Apply gypsum and mulch.:Create soil conditions that suppress
    development of Phytophthora root rot

•   Provide appropriate nutrition: Moderate amounts of nitrogen promote
    good growth that helps avocado better tolerate root rot. Avoid excess
    amounts of fertilizer, especially avoid large amounts of animal manures or
    other products high in ammonia or salts. Avocado roots are sensitive to
    ammonia and salts.

•   Rotate crops.

•   Chemical control: Certain phosphonate fungicides (phosphorous acid and
    phosphonate compounds) can markedly improve trees' ability to tolerate,
    resist, or recover from infection by Phytophthora cinnamomi. Good control
    requires using fungicides in combination with other recommended practices,
    such as careful irrigation practices and applying wood chip mulch.
Bacterial Canker
( Xanthomonas campestris )
Symptoms
• Bacterial cankers appear as slightly sunken, dark areas on the bark
  and vary in size from about 1 to 4 inches in diameter.

•    Bark around cankers may crack. Fluid often oozes and dries,
    leaving a white powder around or over the lesion.
•
• Usually cankers appear and spread upward in a line on one side of
  the trunk or branch.

•    Cutting under the bark surface reveals a decayed, reddish brown
    necrotic pocket, which may contain liquid. Dark streaks in the wood
    radiate out both above and below from the lesions.

• Severely affected trees may have pale, sparse foliage and low yields
  on one branch or on the entire tree, but this is rare.
Management
• Normally the disease is a minor problem. Usually no control is
  necessary on established trees.

•   If the disease is severe and yield is affected, remove the tree.

• Keep trees healthy and provide good cultural care.

• Provide appropriate amounts and frequency of irrigation and good
  uniformity of water distribution among trees.

• Use certified, disease-free nursery stock if available. Regularly
  inspect young trees and remove and dispose of young trees if they
  are infected.

• Nurseries should use stringent sanitation, regularly screen stock for
  disease, and dispose of affected trees so they are not planted
Armillary Root Rot (Oak Root
Fungus)
( Armillaria mellea)
Symptoms
• Infected trees usually die prematurely, and young trees often die
  quickly after infection.

• Mature trees may die quickly or slowly, or may recover at least
  temporarily if conditions become good for tree growth and poor for
  disease development.

• Wilted, downward-hanging foliage is often the first obvious symptom
  of Armillaria root rot. Other symptoms include foliage yellowing, leaf
  drop, and dieback of upper limbs. During the rainy fall and winter,
  groups of short-lived mushrooms often grow around the base of
  Armillaria-infected trees.

• The most reliable sign of Armillaria root rot is fungal growth in
  cambial tissue. If trees exhibit aboveground symptoms of infection,
  cut off bark at the base of the tree and crown to diagnose the
  presence of Armillaria mycelium.
Management
• Provide a good growing environment and proper cultural practices
  and use good sanitation to manage Armillaria root rot.

• Providing good drainage and avoiding excess irrigation are
  important.

•   Shade any exposed root crowns from sunburn.

• Once trees die, remove them and any immediately adjacent trees
  that may also be infected. Remove the stumps and as many root
  pieces from the soil as possible. Thoroughly clean all soil from
    equipment and leave soil on-site before removing equipment.
AVOCADO SUNBLOTCH
( Avocado Sunblotch)Viroid ASBVD
Symptoms
• Narrow yellow, red, or necrotic streaks that often are associated with
  shallow lengthwise indentations along the twig.

• Fruit may show white or yellow blotches or streaks that mayor may
  not be depressed.

• Fruit that remains green at maturity usually have white or yellowish
  areas, while fruit that turns black usually have whitish areas that turn
  red as the fruit mature.

• Leaves may have white or yellowish variegated areas, and they
  often are deformed.

• Leaf symptoms are uncommon in the field. Rectangular cracking
  and checking of the bark on the trunk and larger branches ("alligator
  bark").

•   Trees affected by the disease are often stunted and have sprawling
    growth.
Management
• Use of trees registered as disease-free, which involves
  careful selection of disease-free scions and seed
  sources.

• Trees with symptoms should be removed from the
  orchard and remaining stumps should be killed. Indexing
  of suspect orchards can be done to identify positive
  trees. Pruning tools and harvesting clippers should be
  sterilized between trees.

• It is important that pruning tools be disinfected before
  moving from one tree to another.
SCAB
(Sphaceloma perseae )
Symptoms
• On the fruit, spots are first oval, slightly raised, and brown to
  purplish-brown. As the fruit mature, spots coalesce and the centres
  of these spots become sunken . A large portion of the fruit may
  become rough.

• The lesions on the leaves are less well-known and less readily
  observed, because they most often occur in the upper part of the
  tree canopy.

• Scab starts on leaves as discrete, small spots less than 1/8 inch (3.5
  mm) in diameter. The spots are especially common on veins on the
  underside of leaves. As leaf spots develop, they very often take on a
  star-like pattern with the centre eventually dropping out to give a
  "shot-hole" effect.

• Symptoms on petioles and twigs include oval to elongate spots that
  may, on hurried inspection, be confused with scale insects.
Management
• Scab infection is favored by cool, moist conditions. This fungus is a
  pathogen of young tissue.

• The fruit of all varieties become resistant once they reach about half
  size.

• Chemical sprays play an important role in the adequate control of
  this disease.

• There is considerable variability among varieties in their
  susceptibility to scab. Lula, Hall, and most avocado seedlings are
  very susceptible.

•   The varieties Booth 3, 5, 7, 8; Monroe; Choquette; and Trapp are
    moderately susceptible. Waldin, Pollock, Booth 1, and Collins are
    only slightly susceptible.
CERCOSPORA SPOT
(Cercospora purpurea)
Symptoms
• Individual spots on leaves are very small and brown to purple in
  color.

• The angular appearance of the leaf spots is highly diagnostic Many
  of these leaf spots are surrounded by yellow haloes.

• During the rainy season, grayish spore masses may be seen on the
  surface of the spots with a hand lens. Individual leaf spots may
  coalesce to form irregular areas of brown tissue.

• On the fruit, damage begins as small, irregular, brown spots that
  enlarge and coalesce. Fissures often appear in these spots and are
  very commonly entry points for the anthracnose fungus.

• Wind and rain play an important role in dissemination of C. purpurea
  spores. Insects may also spread the pathogen. The most favorable
  time of year for fruit infection appears to be during the rainy season
  from May through September.
Management
• The disease can be controlled to a great degree by
  timely fungicide applications. However, control is more
  difficult and requires more fungicide use for late-maturing
  varieties, such as Lula and Choquette.
ALGAL LEAF SPOT
Symptoms
• Produces leaf spots on avocado, barely visible at first, but attaining
  1/4 inch (6.2 mm) in diameter within a few months.

• The slightly raised roughly circular spots are green, yellowish-green,
  or rust colored, with rather smooth or fringed margins.

• The alga eventually produces rust-colored, microscopic "spores" on
  the raised surfaces of spots . For this reason, the disease is
  sometimes called red alga spot.

• Young spots are visible on the upper leaf surface. Later, as they
  enlarge and become gray to white, they discolor the opposite, lower
  side of the leaf dark green, olive-green, or brown. A yellowish halo
  may surround these old spots.

• Wind and rain carry the "spores" from diseased to healthy leaves.
  Copper fungicides used for other avocado diseases have provided
  control in the past.
Management
• Wind and rain carry the "spores" from diseased to
  healthy leaves.

•   Copper fungicides can be used for control this.
POWDERY MILDEW
Symptoms
• Powdery mildew, caused by the fungus Oidium, is a sporadic
  disease affecting only avocado foliage.

• On young leaves the powdery mildew spots are dark green and
  covered with a dry powdery layer of the causal fungus.

• On mature leaves, these spots turn purplish brown with a whitish
  fungal growth. These spots eventually lose their undersurface fungal
  coating, and leave distinctive net-like, brown blotches on the
  undersurface.

•   Yellowish areas may later appear on the upper leaf surface,
    opposite the net-like lesions.
Management
• Powdery mildew can occur in all seasons, but can be
  particularly bad during cool, dry times of the year.

•   If the trees are being sprayed for the other diseases
    mentioned above, the disease severity is not thought to
    be above a damage threshold for the crop.
DISEASES OF PINEAPPLE
    Diseases of Pineapple
 (Ananas comosus (L.) Merr.)

BACTERIAL DISEASE

• Bacterial heart rot
       Erwinia chrysanthemi
FUNGAL DISEASES

• Anthracnose - Colletotrichum ananas
• Butt rot - Chalara paradoxa
• Leaf spot - Curvularia eragrostidis
• Phytophthora heart rot - Phytophthora
  cinnamomi
• Root rot - Pythium spp.
• Seedling blight - Pythium spp.
• White leaf spot - Chalara paradoxa
NEMATODES, PARASITIC

• Lesion - Pratylenchus brachyurus

• Reniform - Rotylenchulus reniformis

• Root-knot - Meloidogyne javanica

• Spiral - Helicotylenchus spp.
VIRUS AND VIRUSLIKE
 DISEASES

• Mealy bug wilt
          Unconfirmed virus/toxin

• Yellow spot
          Tomato spotted wilt virus
FRUIT DISEASES (BACTERIAL)

• Acetic souring
        Acetic acid bacteria
• Bacterial fruitlet brown rot
        Erwinia ananas pv. ananas
• Fruit collapse
         Erwinia chrysanthemi
 • Marbled fruit
       Acetobacter spp
       A. peroxydans
      Erwinia herbicola
•Pink fruit
     Acetobacter aceti
     Erwinia herbicola
     Gluconobacter oxydans
•Soft rot
    Erwinia carotovora subsp
   FRUIT DISEASES (FUNGAL)
• Aspergillus rot - Aspergillus flavus
• Botryodiplodia rot - Lasiodiplodia
  theobromae
• Black rot (water blister) - Chalara
  paradoxa
• Fusariosis - Fusarium subglutinans
• Glassy spoilage - Yeast species
• Interfruitlet corking - Penicillium
  funiculosum
• Leathery pocket - P. funiculosum
• Nigrospora fruit rot - Nigrospora sphaerica
• Phytophthora - Phytophthora nicotianae
• Rhizopus rot - Rhizopus oryzae
                     R. stolonifer.
• Yeasty fermentation - Yeast species
FUNGAL DISEASES
 BUTT ROT - Thielaviopsis
 paradoxa

Symptoms

• Freshly cut or injured tissue is infected
• Soft black rot with dark colored mycelium
  and arthrospores develops
Control

• Freshly cut pineapple should not be planted
  unless treated with a fungicide or dried out.

• To prevent the spread of the pathogen,
  avoid wounds to tissue and remove infected
  pineapple plants
White leaf spot - Ceratocystis paradoxa/
        Thielaviopsis paradoxa
•
    The first symptoms of white leaf spot is
    the appearance of small, light brown to
    yellow spots on the middle or upper part
    of the leaves.

• Under moist conditions the spots
  increase in size, the infected tissues dry
  out and show a grayish to white color
Management

• Common pineapple disease, it causes only
  slight damage to the pineapple crop. Due to
  that no control measure would be justified.
       Phytophthora heart rot-
       Phytophthora nicotiana
Symptoms
• Symptoms of rotting appeared at the base
  of the leaves, in the centre of the leaf
  whorl (heart) of young non-flowering plants

• The leaves had turned brownish red and
  could be easily pulled off. The base of the
  infected leaves had dark brown to black
  zones
Leaves from plant with heart rot
           disease
Management

• High rainfall and low temperatures favor the
  disease development.
• Dipping the propagating material in a
  fungicide solution followed by one spray
  application three to four weeks after
  planting, and another spray application one
  week after forcing
• Soil drainage has to be improved, and
  liming avoided
    Root rot- Pythium species
• Enhanced by high rainfall, low temperature, poor
  drainage and alkaline reaction of the
• Infects the pineapple plant through the root tip and
  the infection can occur at any stage of the plant
  development.

Symptoms
  Change in color of the leaves from the normal
  green to yellow, then brown.
  The leaves curl and dry progressively from the tip
  towards the base
Root Rot Symptoms
Management
• cultural practices
 Plants should be set on raised beds
 soils should be
         light,well aerated,
         drain well and quickly

• Planting in infected soils should be carried out
  in seasons unfavorable to P. cinnamomi
   (to establish a good root system before
  occurrence of conditions favorable to
  infection.)
• treat the propagating material before
  planting, and/or to fumigate the soil to
  reduce the initial inoculum.
• The soil pH plays an important role on
  root rot development since the incidence
  of the disease is reduced in lower pH soils.
VIRUS DISEASES
 Mealybug or pineapple wilt
          virus
caused by a complex of two viruses (PMWaV-1 and
  PMWaV-2) with the mealybug (an insect) as their
  vector
Warm weather favours the build-up of mealybugs
• Older plants are less susceptible than younger plants

Symptoms
• plants become yellowish-red to bright red at the leaf
  tips, this colouration spreading down the leaf
• inner heartleaves remain normal

• Severely infected plants become stunted and produce
  small, undergrade and immature fruits.
• The first effect of the disease usually
  appears in the roots, which stop growing,
  collapse and then rot
• Results in leaves symptoms similar to the
  effect of drought. The root system
  collapses and rots before the first leaf
  symptoms appear.
Red Leaf Symptom
                Management

• Use planting material from wilt-free areas.
• Plant resistant varieties if available. Some
  varieties of pineapple are more resistant to
  the virus than others,
• The variety Cayenne (and 'Masmerah') being
  highly susceptible. 'Singapore Spanish'
  shows some resistance
• Heating pineapple crowns in a large water
  bath at 50°C for 30 minutes permitted 100%
  plant survival and rendered 100% of the
  plants free of pineapple wilt-associated-virus
• Control of the mealybugs using albolineum
  oil (white oil) is one way to get rid of the
  red leaf symptoms
FRUIT DISEASES
 (BACTERIAL)
Pink Disease-      Acetobacter aceti
                    Erwinia herbicola

Symptoms
• Difficult to observe in the field since
  outward symptoms are not apparent
• Development of a brown color in the flesh
  when heating the infected fruits in canning
  process
Pink disease symptoms on pineapple fruit slices originating from a
canned product. Healthy fruit (top), and diseased fruit (bottom).
Management

• Harvesting the fruit before completely ripe

• Promoting fruit production in season
  unfavorable to the disease development

• Dusting the fruits with Dissulfoton during
  the open flower stage
FRUIT DISEASES(FUNGAL)
Fruitlet core rot -Fusarium moniliforme
Symptoms
• light to dark brown soft rot of the fruitlet
  core area
• The disease extends from the base of the
  style, nectary ducts or placenta towards
  the core
• Infected tissue becomes corky, thus
  originating a dry rot
• Cross-section of fruit with fruitlet core rot
             Leathery pocket
              P. funiculosum
• In areas where pineapple is grown for canning,
  leathery pocket is at times a serious disease since
  it reduces slice recovery, thus resulting in losses
  to the industry

Management

• applying Endosulfan, 0.05% a.i., in 2500 l of
  water/ha at 4 week intervals from 5 weeks before
  forcing to 11 weeks post forcing
   Bacterial diseases-
•   Bacterial spot -Xanthomonas campestris
•   Blast           -Pseudomonas syringae
•   Citrus canker   -Xanthomonas axonopodis
                    =Xanthomonas campestris

    Fungal diseases
    Powdery mildew        -Oidium tingitaninum
    Anthracnose = wither-tip
                          -Colletotrichum gloeosporioides
    Damping-off          - Pythium sp.
    Alternaria brown spot -Alternaria alternata
•       Viral diseases

• Citrus mosaic-Satsuma dwarf-related virus
• Tristeza     -Citrus Tristeza Virus(CTV)
•       Nematodes
• Citrus nematode-Tylenchulus
  semipenetrans
Citrus blast        Lemon fruit showing
affecting twig of   lesions caused by
                    citrus blast bacterium.
orange.
Powdery Mildew on
Orange Citrus Tree
leaves.
Advanced symptoms         Ringspots on fruit of 'Satsuma'
caused by the Citrus      mandarin affected by Citrus
Tristeza virus in sweet   mosaic virus.
orange
                  Nematodes

• The citrus nematode,
  Tylenchulus
  semipenetrans,
  causal agent of 'slow
  decline' of citrus, is a
  small microscopic
  worm which feeds
  within the roots of
  citrus.
 REFERENCES:
http://www.google.lk/webhp?hl=en&tab=iw#hl=en&source=hp&biw=1024&
bih=578&q=AVOCADO&aq=f&aqi=g10&aql=&oq=&fp=7b54894fb19cfce5

http://www.google.lk/webhp?hl=en&tab=iw#hl=en&biw=1024&bih=578&q=
PINEAPPLE&aq=f&aqi=g10&aql=&oq=PINEAPPLE&fp=7b54894fb19cfce

http://www.google.lk/webhp?hl=en&tab=iw#hl=en&biw=1024&bih=578&q=
    CITRUS&aq=&aqi=g10&aql=&oq=CITRUS&fp=7b54894fb19cfce5
THANK YOU

				
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