papaya disorders - plantwise3 citrus mealybug planococcus citri • adult female, pinky/white and...

KNOWLEDGE FOR LIFE

Papaya disorders

CABI PEST AND DISEASE PHOTOGUIDE TO

IntroductionThis photo booklet has been produced by the CABI-led Plantwise programme (www.plantwise.org) to aid extension officers and other plant health advisors in diagnosing the most common pests, diseases and abiotic problems of coffee around the world. The symptoms presented on a real plant sample can be compared with the photos in this guide to identify possible causes.

The booklet is organized into two broad sections, one showing the common insect pests that attack the crop and the other showing the various symptoms of poor health. In the symptoms section, the images are arranged by plant part, with similar-looking symptoms displayed together. Some biotic and abiotic factors cause more than one type of symptom, so there may be multiple images in different parts of the photo booklet for a specific problem. The photos for a particular problem are cross-referenced to make it easy to find all the relevant photos.

Contents

Sign or symptom Box #

Insects and Mites 1–9

Leaf 10–16

Edible portion 17–32

Whole Plant 33–38

Root 39–41

1

Papaya Fruit Fly Toxotrypana curvicauda

• Very characteristic insect which lays its eggs through the papaya fruit into hole in the middle of the fruit.

• The maggots feed on the developing seeds and fruit in the centre of the fruit.

• The mature maggot tunnels out of the fruit and pupates in the soil.

• Infested fruits turn yellow and fall early.

Photo: Jeffrey W. Lotz, Florida Department of Agriculture and Consumer Services, Bugwood.org

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2

Oriental Fruit Fly Bactrocera dorsalis

• Brown and yellow fly; slightly smaller than a housefly.

• Lays eggs below the skin of the fruit.

• Larvae (maggots) hatch and feed inside the fruit almost immediatley.

• The fruit often falls off and the maggots leave the fruit to pupate in the soil.

• This pest is not seasonal, it occurs continuously throughout the year in many areas.

Photo: USDA, Flickr

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3

Citrus MealybugPlanococcus citri

• Adult female, pinky/white and covered in wax.• Females suck sap and cause wilting, yellowing and stunting.• The honeydew they produce often leads to sooty mould.• The little white fingers around the insect edge are more

obvious than on the Papaya Mealybug.

Photo: Charles Olsen, USDA APHIS PPQ Bugwood.org

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4

Papaya Mealybug Paracoccus marginatus

• Body yellow, covered with wax but this is not thick enough to hide body colour.

• Heavy infestations cause distortion of new growth, leaf yellowing, leaf curl and early fall of fruit.

• The honeydew they produce often leads to sooty mould.

Photo: United States National Collection of Scale Insects Photographs, USDA Agricultural Research Service, Bugwood.org

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5

White Peach Scale Pseudaulacaspis pentagona

• Males and females look quite different and both are pests.• The adult female (shown) cannot move on the plant. Small,

circular insect (up to 2mm diameter). Conical in shape there is a darkened tip to the cone.

• Males are mobile and appear as tiny grains of rice.

Photo: S. Nelson, Flickr

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6

Snow ScaleUnaspis citri

• The young (nymphs) are ‘crawlers’ because this is the dispersal stage. Nymphs are oval and bright yellow in colour.

• Nymphs form a waxy armour. The snow white armour of the immature male is the reason for the name. The coat has three long ridges; one prominent centre ridge, and one either side.

• Immature males are about 1 mm long.

Photo: Lisa Ames, University of Georgia, Bugwood.org

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7

False Spider Mite Brevipalpus phoenicis

• Very small, flat reddish; moves around very quickly on the surface of leaves or fruit. Hand lenses are needed.

• Can create marks, scarring and sometimes a mosaic on leaf and fruit skin.

• Reduces plant vigour and affects the taste of the fruit.

Photo: Rayanne Lehman, Pennsylvania Department of Agriculture, Bugwood.org

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8

Fruit Piercing MothEudocima fullonia and others

• Not a pest of papaya and does not feed on papaya, it is the adult form that is the pest.

Photo: Arian Suresh, Flikr

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9

Fruit Piercing Moth Eudocima fullonia and others

• Moths feed at night by piercing the skin of the ripe or ripening fruit with their strong mouth parts.

• Internal injury consists of a bruised, dry area beneath the skin.

• Secondary rots develop at the feeding site.• Secomdary-moth feeders often visit fermenting fruit,

using the holes the fruit piercing moths have made.

Photo: BRIJESH EP, Flickr

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10

Broad Mite Polyphagotarsonemus latus

• Edges of damaged young leaves usually curl. The foilage often becomes rigid and stiff, it appears brown (bronzed) or scorched.

• Leaves are very small and do not expand properly.• Mites are too small to be seen even with a handlens.


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11

Powdery Mildew Oidium caricae

• Lower leaf surfaces spotted with small water soaked yellow dots that become powdery patches of fungus and spores; patches are usually near the veins and are more clearly seen in humid conditions.

• Yellow patches later become necrotic (brown) and scorched; leaves may curl and fall from trees early.

Photo: S Nelson, Flickr

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12

Papaya Mosaic Virus PaPMV

• Symptoms of infection include mild leaf mosaic and stunting.• No symptoms appear on leafstalks, stems or fruit.• Stunting is only obvious when healthy plants are present for

comparison this disease is considered of little importance.

Photo: William M. Brown Jr.,Bugwood.org

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13

Black Spot Asperisporium caricae

• Lesions start as water soaked spots that become brown. These develop into pale circular leaf spots up to 4 mm diameter often surrounded by a yellow ring.

• Young leaves are not attacked but severely damaged older leaves fall off and up to half of the leaves can fall off causing a reduced vigour.

• Disease is favoured by wind and rain for dispersal.


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14

Corynespora Brown Spot Corynespora cassiicola

• Pale yellow lesions with brown centres on upper leaf surface, 1-2 mm in diameter but can join together into larger areas.

• On lower leaf surface small light and water soaked brown spots with yellow halo, turning necrotic.

• All lesions become brown and sunken with reddish margins; spores are more apparent on lower surfaces.

• Lower leaves are particularly susceptible.

Photo: Ecoport (http://ecoport.org): Landcare Ltd New Zealand

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15

Papaya RingspotPapaya ringspot virus (PRSV)

• Mottling and mosaic of leaves; leaf lobes are reduced, giving a shoe-string apperance.

• This distortion becomes more obvious as the disease progresses.

• Severley affected trees infected at a young age will not produce a good crop.


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16

Papaya DiebackErwinia papayae

• The pathogen attacks the top of the leaf stalk causing yellowing and then browning.

• The leaf collapses and will turn brown.• If the tip of the plant is infected the whole plant will rot and die.• Symptoms can look like Phytohpthora infection but split the

stem as Phytophthora usually starts at the bottom and other infections start at the top of the tree.

Photo: Thaddeus Peters, Ministry of Agriculture Lands, Forestry, Fisheries and Environment, Grenada

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17

White Peach Scale Pseudaulacaspis pentagona

• Causes leaf chlorosis and twig die back.• Produces honeydew leading to sooty mould which

can reduce plant vigour and cause death of tree if severe.• Common on leaves and fruits.


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18

Snow Scale Unaspis citri

• Can reach extremely high numbers on fruit and leaves.


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19

Phytophthora Blight Phytophthora palmivora

• Fruit rot initially appears as small, circular, water-soaked spots about 5-10 mm in diameter.

• Large lesions, often forming first where the fruit touches the stem of the plant.

• As the pathogen spreads within the fruit it becomes covered with whitish fungal growth and masses of Phytophthora sporangia.


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Grey Mould Botrytis cinerea

• An opportunistic pathogen that will attack weak and over-ripe fruit.

• Will occur in times of high humidity and especially on damaged fruit.

• A characteristic grey fluffy (fuzz) of spores will cover the rot which gradually spreads over all of the fruit.


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Mites Various species of mite

• The mites scratch the surface of the developing fruit which responds by producing sap (latex).

• The milky white sap will dry on the surface of fruit leaving ugly dry scabs.


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Black Spot Asperisporium caricae

• Lesions start as water soaked spots that become necrotic (brown). These develop into pale shallow circular lesions up to 10 mm diameter often surrounded by a chlorotic halo. There is no tissue decay beneath.

• The white zones in the photo are fungal parastites of the pathogen and not the pathogen itself.


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• Fruit from infected trees have ringspots on the skin (they are not actual spots). The ringspots can be very light at the beginning of the disease and gradually increase in number and colour.

• Fruit is not produced on severely affected plants.• Can sometimes be confused with Tomato spotted wilt virus.


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24

Collectotrichum Rot Glomerella cingulata

• Round, water-soaked, sunken spots, can become as large as 50 mm diameter. Turning pinkish orange, with fungal masses in the centre.

• Often present on over-ripe fruits.

Photo: Thaddeus Peters, Min of Ag, Grenada

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25

Oriental Fruit FlyBactrocera dorsalis

• Small puncture wounds with circular halos on the fruit surface; rotting of the skin.

• The puncture holes often allow other diseases to attack the fruit, making the fruits difficult to sell.

Photo: William M. Brown Jr., Bugwood.org

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26

Colletotrichum Rot Glomerella cingulata

• Small water-soaked spots appear on the fruit surface as ripening commences.

• Circular sunken lesions with light brown margins form, with pink fungal masses in the centre.

• Internal tissue is firm with a greyish white discolouration.

Photo: J. Waller, CABI

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27

False Spider Mite Brevipalpus phoenicis

• Causes marks, scarring and sometimes a mosaic on leaves and fruit skin.

• Reduces plant vigour and affects the taste of the fruit.


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28

Powdery MildewOidium caricae

• Mildew on immature fruit begins as circular patches of white powdery material that join together and cover the entire fruit.

• As the fruit ripens, the fungus may disappear leaving behind grey scars.


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29

Papaya MealybugParacoccus marginatus

• Fruit may become completely covered by a layer of mealybugs and wax secretions.

• Heavy infestations may cause early fruit fall.• When infested the fruit loses value or cannot be

sold at markets.

Photo: C. Njuguna, IITA

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30

Black RotMycosphaerella caricae

• Mainly attacks young fruits, usually at the point of contact with dead leaves.

• Can affect ripening fruits through broken fruit stalks.• Small, dark, sunken, water-soaked regions; wrinkled fruits.• Fruits may oose sap.


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Black SpotCercospora sp.

• Tiny Black dots on fruit which enlarge to 3 mm across; spots are slightly raised and although indistinct on unripe green fruit.

• Become visible on ripening to yellow; lesions on leaves are irregular in shape and grey-white in colour; if infection is severe, leaves may turn yellow and die and drop from plant.

Photo: Wayne Nishijima, Flickr

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32

Shortage of BoronBoron deficiency

• Symptoms first appear in new growth.• The leaves appear brittle and distorted.• Affected fruit are seedless, ripen unevenly and are covered

in lumps.• Affected trees can lose up to 100% of their fruits.


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33

Papaya Bunchy Top Papaya bunchy top virus or candidatus phytoplasma carica

• Irregular water-soaked marks at the base of the leaf stem.• Fruiting or latex discharge rarely occurs on severely

infected trees.• Can be found with other symptoms on the younger leaves.• These two causes are extremley difficult to tell apart in

the field.

Photo: P. Taylor, CABI

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34


• Leaves develop prominent mosaic and chlorosis on the leaf lamina and water soaked oily streaks on the petioles and upper part of the trunk.

• Severe symptoms often include a distortion of young leaves which also result in the development of a shoestring appearance that resembles mite damage.


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35

Damping OffPhytophthora/Pythium spp.

• Shoots and roots are necrotic; seedlings necrotic with watery roots; seeds have watery rots.

• If the plant is older, infections are not as lethal, but they can still have a significant impact on plant growth and yield, particularly in abnormally hot and windy weather.

Photo: R. Williams, CABI Crop Compendium

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36

Shortage of Iron Iron deficiency

• Yellowing between the veins which appears as a green network of veins on leaves.

• The symptoms are seen in the younger leaves first.• Fruit may be low in sugar.

36DEFICIENCY

Photo: S.Nelson, FlickrBA

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37

Papaya Bunchy TopCandidatus phytoplasma carica

• Upper leaf mottling and yellowing between leaf veins, leaves are thickened and the edges may turn brown.

• Tree leaves and leaf stalks are smaller (shorter internodes), giving a bunchy top appearance.

• Fruits can become bitter and the entire tree may die.

Photo: Reuben Raymond, Caribbean Agricultural Research and Development Institute, Grenada

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38

Papaya DiebackErwinia papayae

• Infection of the main trunk.• Note the ooze from the centre of the lesion (with maggots

feeding on the ooze).• The outside of the plant rots away leaving the fiberous

material inside.

Photo: Thaddeus Peters, Ministry of Agriculture Lands, Forestry, Fisheries and Environment, Grenada

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39

Root RotPhytophthora/Pythium spp.

• Browning of the inside of the roots.• Damage start at the ends of the secondary roots and

progresses towards the inside of the primary roots.• Rot is at the base but general wilting and stunting

of the plant/tree from the top down.


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40

Root Knot nematodeMeloidogyne spp.

• Lumps or galls of between 1 and 10 cm on the roots. Heavily galled roots may rot away.

• Tree or plant growth stunted, starts to wilt, followed by a general chlorosis. This can result in the death of the tree if severely infected roots are continually attacked.


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Phytophthora root rotPhytophthora palmivora

• Side roots of young plants (less than 3 months old) are most susceptible in wet soils.

• Roots may become dark and rotten, causing stunting of plant growth and yellow, collapsed leaves.

• Severely infected plants may die. Plants with a heavy load of fruit may fall. Papaya plants with rotton roots are susceptible to drought.


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KNOWLEDGE FOR LIFE

AfricaGhana CABI, CSIR Campus, No. 6 Agostino Neto Road Airport Residential Area, P. O. Box CT 8630, Cantonments Accra, Ghana

T: +233 (0)302 797 202 E: [email protected]

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T: +254 (0)20 2271000/20 E: [email protected]

Zambia CABI, 5834 Mwange Close, Kalundu, P.O. Box 37589, Lusaka, Zambia

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T: +5514 38117670 E: [email protected]

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T: +1 868 6457628 E: [email protected]

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AsiaChina CABI, Beijing Representative Office, Internal Post Box 56 Chinese Academy of Agricultural Sciences 12 Zhongguancun Nandajie, Beijing 100081, China

T: +86 (0)10 82105692 E: [email protected]

India CABI, 2nd Floor, CG Block, NASC Complex, DP Shastri Marg Opp. Todapur Village, PUSA, New Delhi – 110012, India


Malaysia CABI, PO Box 210, 43400 UPM Serdang, Selangor, Malaysia


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T: +92 (0)51 929 2064/2063 E: [email protected]

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EuropeSwitzerland CABI, Rue des Grillons 1 CH-2800 Delémont, Switzerland


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UK CABI, Bakeham Lane Egham, Surrey TW20 9TY, UK

T: +44 (0)1491 829080 E: [email protected] E: [email protected]

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papaya disorders - plantwise3 citrus mealybug planococcus citri • adult female, pinky/white and...

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