HOST PLANT RESISTANCE, CULTURAL AND MECHANICAL CONTROL IN COCOA

R. Adu-Acheampong, A. R. Cudjoe, Y. Adu-Ampomah, K. Gorkeh-Sekyimwww.crig.org

1

World cocoa production

2

Cocoa is an important cash crop in West Africa

W. Africa produces 70% of the world cocoa

Major biotic and abiotic stresses to cocoa production

Black pod diseaseWitches’ broomFrosty podSwollen shoot virus diseaseVascular streak diseaseMistletoes

Mirids and associated fungiCocoa pod borerPlanting materialsSoil fertility

4

Pink diseaseWhite threadsStink bugsStem borersTermitesPod feeders

5

Emerging disease and pest problems in West Africa

6

Black pod disease problem of CocoaBlack pod caused by several species of Phytophthora is one of the most-important diseases affecting cacao

In Central and West Africa. P. megakarya is the species that causes most damage (up to 80% of pod losses).

Witches’

broom (left) caused by Crinipellis perniciosa

Photo: USDA, SPCL

7

Frosty Pod caused by Moniliophthora roreri Photo: USDA, SPCL

8

More than 230 million infected cocoa trees have been destroyed due to CSSVD (Dr Henry Obiatey, pers. comm.)

9

Cocoa swollen shoot virus disease problem

THE COCOA MIRID PROBLEM

FungiFungi

Adult of S. singularis

Various Fusarium species from mirid feeding lesions

11

History of mirid control

Mainly by insecticides against miridsKerosene & soap emulsion (1908-1920s)Sulphur compounds (1920s to early 1940s)DDT (mid 1940s to early 1950s)Lindane* & other organochlorine insecticides (early 1950s to 1960s) [*Banned in 2001]Organophosphorus, carbamate* and pyrethroid insecticides (mid 1960s to 1970s) [propoxur banned in 2001]Nitroguanidines (late 1990s to date)

Need for alternatives to pesticide use for increased environmental and biodiversity protection

13

Plants have natural defence mechanisms

Physical barriers

Fungitoxic compounds

Hypersensitive response

Production of phytoalexins14

1. HOST PLANT RESISTANCE

15

Cocoapresents a wide biological diversity

HOST PLANT RESISTANCE TO INSECTS AND DISEASES

Selecting cocoa germplasm lines that have resistance or tolerance to insects or diseases makes it possible to avoid or lessen the use of pesticides

16

Identification of pathogens

17

Methods of disease and pest resistance screening in cocoa germplasm

A leaf inoculationAutomated spray inoculation –witches’ broom Use of vegetatively propagated plantsAgar droplet methodField observations

18

19

Activity: Laboratory micro-test experiments for mirid resistance

20

Activity: Laboratory cage experiments for mirid resistance

21

Activity: Sleeve cage experiments for mirid resistance in the field

Disease resistance

Success of pathogen entryFunctional plant loss indices

Incubation & latent periodsLesion lengths/area under the lesion expansion curve

Rates of disease progressionPercent biomass loss

Insect resistanceFeeding damageAntibiotic effectsRecords of survival timesFecundity Foliar area damageQuantifying chlorophyll loss by feeding

22

What do we measure in host plant resistance studies?

Examples of laboratory and field screeningA polygenic control of black pod disease has been suggested (Enriquez and Soria 1996)

A leaf inoculation method by Nyass (1997) and a significant positive correlation between leaf-test data and pod-rot rate in the field was observed.

Results suggested a leaf test could be used as an early predictor of black pod resistance in the field.

23

Some published works

Ahnert, D, and Pires, JL (2000) Use of the available genetic variability of cocoa in Brazil. In: Technical Meeting: State of the Knowledge on Mass Production of Genetically Improved Propagules of Cocoa, 104-113. Ilhe´us, Brazil.

Crouzillat, D, Phillips, W, Fritz, PJ and Petiard, V (2000) Quantitative trait loci analysis in Theobroma cacao using molecular markers: inheritance of polygenic resistance to Phytophthora palmivora in two related cacao populations. Euphytica 114, 25-36.

N’Guessan, KF, N’Goran, JAK, Eskes, AB (2004) Mirid resistance studies in Cote d’Ivoire: assessment of antixenosis, antibiosis and tolerance. In: Eskes, A.B., Efron, Y. (Eds.), Global Aproaches to Cocoa Germplasm Utilization and Conservation, pp. 177–186.

24

Some published works cont’dSteven Brown, J, Phillips-Mora, W, Power, EJ Cuauhtemoc Cervantes-Martinez Cheryl Krol, Juan Carlos Motamayor and Raymond J. Schnell (2006) Mapping QTLs for Resistance to Frosty Pod and Black Pod Diseases and Horticultural Traits in Theobroma cacao L. (2006) Crop sci. 47 (5) 1851-1858

Teh, C-L, Pang, JT-Y, and Ho, C-T (2006) Variation of the response of clonal cocoa to attack by cocoa pod borer Conopormorpha cramerella (Lepidoptera: Gracillariidae) in Sabah. Crop Protection 25 (7) 712-717

Queiroz, VT, Guimaraes, CT, Anhert, D, Schuster, I, Daher, RT, Pereira, MG, Miranda, VR M, Loguercio, LL,, Barros, EG, and Moreira, MA (2003) Identification of a major QTL in cocoa (Theobroma cacao L.) associated with resistance to witches’ broom disease. Plant Breeding 122, 268-272 25

2. Cultural, Quarantine & Environmental manipulation

shade reduction and managementMixed farming systemsPruning and destruction of infected plants/plant partsRegular harvesting removal and burying of infected podsRestrictions on plant movementfrequent weed controlBarrier croppingEntomopathogens

26

IMPROVING HABITATS FOR BENEFICIAL INSECTS

Avoiding pests by intercropping cocoa with food crops

Increasing plant complexity to provide sites for beneficial insects is a recommendation for cocoa establishment

27

3. Use of plant based pesticides

aqueous neem seed extract

pyrethrum

28

29

4. Use of insect sex attractants

30

Certification of cocoa farms Organic cocoa farmers are responding well to IPM strategies allowing them to market their produce as pesticide-safe or organic .

INNOVATIONS FOR DISEASE AND INNOVATIONS FOR DISEASE AND PEST CONTROLPEST CONTROL

Stakeholders learning and innovating together for improved benefits

31

Strengths in alternative disease and pest control in cocoa

Strict quarantine restrictions on trans-continental movement of materialsContinuous development and improvement of screening protocolsPersonnel and information exchange and collaboration between the north and the south

32

Key challenges in alternative disease and pest control in cocoa

There is no standardised protocols and resistance assessment systems are subjectiveThere is always the compounding effect of climate change- drought and desertification etcCocoa is primarily monoculture and new stresses should be anticipated There are loads of alternative hosts for pests

33

34

CollaborationNeed for continued collaboration

• Building the tools to sustainably control pests and diseases threatening cocoa production...

... building the required database through exchange of useful information!

Questions?35