FUNGAL PLANT DISEASES

Case Study Of

PHYTOPHTHORA POD OF

CHOCOLATE TREE (Theobroma cacao)

RUFUS J. AKINRINLOLAGrad Student, Plant Pathology Department,University of Nebraska Lincoln,November 23rd, 2015

OUTLINE What is Theobroma cacao Importance of Theobroma cacao Fungal diseases of Theobroma cacao Black pod disease (Phytophthora pod rot) Disease Cycle and Mode of Dissemination Signs and Symptoms Dsease Managements Managements Limitations Summary References

Theobroma cacao

Cocoa Tree Cocoa is a tree plant growing upto the height of 10metres. Is an understory plants –grows under larger tropical forests trees.Cocoa pod may contains upto 30 to 40 cocoa beansCocoa starts fruiting after 4 to 5 years of Planting.Cocoa tree is a perennial crop

Image source: http://www.santabarbarachocolate.com/

Theobroma cacao

http://www.worldwatch.org/photohttp://www.technoserve.org/

Theobroma cacao

History and OriginThe cocoa plant is indigenous to the tropical rain forests of South and Central America First discovered by Olmecs (1500-400 BC)- first major civilization in Mexico

Named by Swedish natural scientist Carl Linnaeus, as Theobroma cacao

Theobroma is a Latinized Greek word: “theo” means “god”, and “broma” means “nectar” or “food”.

Theobroma cacao

Historical relevance First consumed by the Olmecs as chocolate drinks Used as monetary and measurement units Used in religious rituals as a dedication to Quetzalcoatl, the god of cocoaUsed as offerings at the funeral of noblemenCocoa drink was only available for the privileged and the soldiers during

battle

Theobroma cacao

Cocoa worldwide growth --regions and environmental factors Cocoa grows best in tropical regions, between approximately 20° north and 20° south of

the equatorMost cocoa is grown at an altitude of about 1,200 feet above sea levelThe Ideal temperatures are between 65°F to 90°F (18°C and 32°C).Annual rainfall range, between 1,000 and 3,000 mm (400 to 1,100 inches) per year.Usually requires protection from direct intense sunlight and excessive winds.

Theobroma cacao

Source: http://beannco.com/

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Worldwide cocoa production

Economic Importance of Theobroma cacao

Social and economic impact

Employment Income source Improved quality of life Cash crops to many nations

Export earnings from cocoa

Cocoa bean Semi-finished (Cocoa powder, cocoa

butter) Finished products (chocolate) Global trade of cocoa bean worth $9

billion dollars

Diseases and Pests of Theobroma cacao

--Fungal diseasesBlack pod or Phytophthora pod rot:- Phytophthora sppMonilia or Frosty pod rot :- Moniliophthora roreri Witches’ broom :- Crinipellis perniciosaVascular streak dieback:- Orcobasidium theobromae

--Pests Cocoa swollen shoot virusCocoa stem borerCocoa mirid:-Distantiella Theobroma, Sahlbergella singularis, Helopeltis spp, Monalonion spp.Cocoa mealybugs:- Planococcus spp. Pseudococus spp.

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PHYTOPHTHORA POD ROT DISEASE

Also called Black pod disease of cocoa or PPRCaused by the Omycetes Phytophthora

P. palmivora:- causes global yield loss, covering Africa, Asia and America P. megakarya:-Central and West Africa; most aggressive of the Pod Rot pathogens. P. capsici:-Central and South America,  P. cithrophora:- Central and South America, P. tropicalis

Responsible for the 70% of cocoa pod loss worldwide Main causes of worldwide coca yield loss Can infect the roots, stems, leaves, flowers and pods of cocoa

PHYTOPHTHORA LIFE CYCLE

http://forestphytophthoras.org/

DISEASE CYCLE AND SYMPTOMS

Infection process

I. Initial contactII. Adhesion and encystmentIII. Spore germination and

penetrationIV. Colonization and nutrient

acquisition V. Sporulation

Hardham, A. R. (2001). The cell biology behind Phytophthora pathogenicity.Australasian Plant Pathology, 30(2), 91-98.

DISEASE CYCLE AND SYMPTOMS

Disease symptoms

Necrotic lesion on pods• Discolored spot• Brown or black lesion• Whole pod blackens and shrivels• Rot; Pod tissue, pulps and beans• Chirelle (developing fruit) wilt

Canker on stems

McMahon et al, 2004

DISEASE CYCLE AND SYMPTOMS

Disease Cycle 1. Healthy fruit become infected2. Brown spots appear and develop 5d after

infection3. Brown spots cover the entire pod at 8

days after infection4. At 11 days mycelia cover the entire pod5. Water, ants and insects disperse the spores 6. Hyphae become survival spores in soil

and mummified pods

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Wilbert phlilips – Mora, Rolando Cerda, cacao diseases in Central America. Tropical Agricultural research and Higher education Center (CATIE), Turrialba, Costa Rica, 2009.

MODE OF DISSEMINATION

InoculumSurvival material

Oospores Mycelia Chlamydospores

Primary inoculum Sporangia Zoospores

Secondary inoculum Hypha Cyst

Sources of inoculum

Infected soil and roots Infected flowers and

leaves Infected pods and stems Mummified pods Contaminated

implements

Mode of dissemination:-

Ants Insects Direct contact Rain or water splash Wind Bats

Guest, 2007

MODE OFDISSEMINATION

Conditions that favor Black pod dissemination

High rainfall High humidity Poor drainage Heavy canopy Low hanging branches

BLACK POD MANAGEMENT

Resistant varieties :- Through breeding

Chemical control

Copper based fungicides Cuprous oxide

Metalaxyl

Potassium phosphonate

Phytosanitation

Pruning Removal of lowered branches Regular weeding Regular harvesting of ripe and any infected pods. Burying of infected pods and pod husks Addition of manure

Biological control

Natural antagonists of Phytophthora

Bacillus cereus B. sutilis Penicillium spp Botryodiplodia

theobromae

Plant extracts

BLACK POD MANAGEMENT LIMITATIONS

Chemical controlFungicides spraying is laboriousFungicides are not cost effectiveChemicals are not ecofriendly

PhytosanitationLaboriousStrategy is not enough to curb the disease loss

Biological controlBiocontrol agents react differently in different environments

Resistant varietiesBreeding cocoa varieties takes years

Integrated management

Combining all methods has been the only effective recommended strategy that is able to reduce cocoa yield loss to a bare minimum of about 5-10%, depending on commitment of the cocoa farmer to the stress involved

SUMMARY AND RECOMMENDATION Black pod disease affects world wide cocoa production and responsible for 70% of global cocoa bean lossBlack pod is caused by various species of Phytophthora (Plant destroyer)Phytophthora palmivora has worldwide distribution while megakarya the most aggressive specie is found

in Africa and P. capsici and cithrophora is virulent in south America Wet weather and high humidity favor the disease incidence Various control strategies including fungicides, biocontrol agents and use of resistant varieties are

engaged against the disease.Each control strategy alone is inadequate to curb the disease incidence and often comes with one

limitation or another. Further research is required to discover a more effective and more environment friendly approach to

manage the disease

REFRENCES Acebo-Guerrero, Y., Hernández-Rodríguez, A., Heydrich-Pérez, M., El Jaziri, M., & Hernández-Lauzardo, A. N. (2012). Management of black pod rot in cacao

(Theobroma cacao L.): a review. Fruits, 67(01), 41-48.

Cocoa (cacao) | Diseases and Pests, Description, Uses and propagation, https://www.plantvillage.com/en/topics/cocoa-cacao/infos/diseases_and_pests_description_uses_propagation

Guest, D. (2007). Black pod: Diverse pathogens with a global impact on cocoa yield. Phytopathology, 97(12), 1650-1653.

History of cocoa, http://worldagroforestry.org/treesandmarkets/inaforesta/index.htm

Hardham, A. R. (2001). The cell biology behind Phytophthora pathogenicity.Australasian Plant Pathology, 30(2), 91-98.

McMahon, P., Purwantara, A., Drenth, A., & Guest, D. I. (2004). Phytophthora on cocoa. Diversity and management of Phytophthora in Southeast Asia, 104-115.

Pests and diseaeses of cocoa, international cocoa organization, http://www.Icco.Org/about-cocoa/pest-a-diseases.Html

Tondje, P. R., Roberts, D. P., Bon, M. C., Widmer, T., Samuels, G. J., Ismaiel, A., ... & Hebbar, K. P. (2007). Isolation and identification of mycoparasitic isolates of Trichoderma asperellum with potential for suppression of black pod disease of cacao in Cameroon. Biological Control, 43(2), 202-212.