2.9.1. Cultural practices and chemical control
The main strategy used in the management of CWD in DRC involved the sys- tematic elimination of all the infected coffee trees once the most typical exter- nal symptoms of CWD (yellowing, browning unilateral or general of young shoots, fading and wilting) are observed. If conducted judiciously, then the method has the advantage of reducing pathogen inoculum at the primary centre of infection, thus preventing the spread to neighbouring healthy trees.
For the method to be effective against CWD, the following observations and operations are recommended (Fraselle et al., 1953):
For each field, a detailed plan locating each coffee tree is required.
Regular monitoring is required to detect any coffee bush showing even partial dieback symptoms on the aerial parts of the plant; all doubtful
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plants are clearly identified using visible signs (string, color material or any other marking).
After identifying a plant suspected to be infected by CWD, it is advisable to work in group to confirm whether or not that coffee tree is actually infected.
The disease can be confirmed if the superficial bark is removed on all sides of the stem, and blue–black bands are seen below the bark; this is diagnostic of CWD.
If the suspect tree does not have these characteristic blue–black staining below the bark, then the wounds need to be disinfected and the knife used treated with a chemical or heat treated.
If the suspect tree is infected with CWD, then the plant needs to be clearly marked to identify its location. A spray of 10% carbolineum preparation in water solution (about 2 l of solution) should be applied to the aerial parts of the infected coffee bush.
The infected plants should then be dug out (including the root system).
The tree should be cut into sections and incinerated in situ. If the wood is dry, then this can be done immediately, but if the wood is still green, then a few days may be needed to allow the wood to dry to facilitate burning.
Trials undertaken in situ where the plantations are characterized by the ab- sence of CWD symptoms, but close to infected plantations, allowed an assess- ment of the impact of some agronomic practices and management methods on both the expression and the development of the disease. Protected plants were left to natural contamination, and the assessments consisted of record- ing the numbers of infected plants on a monthly basis.
The agronomic practices tested consisted of clean weeding, slashing and pruning. The clean weeding was obtained by spraying herbicides glypho- sate at 0.1%. The spraying was done in such a way that the herbicide did not touch the coffee tree, that is, by keeping a distance of about 30 cm from the tree. Slashing, which is a common practice of weeding, was made by using the machete. Pruning by means of shears or saw was undertaken. Chemical control was undertaken by monthly spraying of Cupravit (copper oxychlo- ride), a fungicide, at 0.5% (wt/vol) on the base of the coffee trunk and by painting the stem with the same fungicide (0.3% [wt/vol] solution) applied to the trunk at a height of 0.5 m from the soil.
Monthly spraying of fungicide was more effective in reducing the at- tack of CWD than other treatments (Fig. 2.7). This was followed by slashing and clean weeding, which also seem to significantly reduce CWD incidence.
Treatment using stem painting and pruning did not seem to be so effective.
The high prevalence of infected trees, scored in the case of the plots under pruning (6%) and the control plots (7%), demonstrates the danger that might be associated with wounding coffee trees during routine maintenance, and the lack of maintenance or phytosanitary practices in the abandoned planta- tions is also a key cause of the rapid spread of CWD.
The foregoing results obtained in DRC show that besides fungicide spray- ing, agronomic practices that are aimed at maintaining a clean plantation
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such as clean weeding and slashing would, if conducted efficiently, signifi- cantly contribute to reducing CWD spread. Alternatively, any practice that involves wounding, such as pruning, is likely to increase the rate of spread of the disease. Phiri (2005, personal communication) reported the results reg- istered in Ethiopia, Uganda and Tanzania, where the same study was con- ducted at the same period as in DRC, and concluded that the prevention of any wound contributes to reducing and slowing down the spread of CWD in plantations. However, the use of chemical treatment cannot be recommended for our farmers’ fields, given the cost and the danger that it represents for humans and the environment. Agronomic practices such as slashing, if con- ducted appropriately, for example, by avoiding wounds on coffee trees or ensuring that plantations are well maintained, will remain the main method for the management of CWD in DRC and can be easily adopted by farmers.
2.9.2. Availability of the improved material for replanting
The current situation in DRC with respect to CWD requires rehabilitation of existing production areas and the extension of these production areas using planting material of desirable characteristics. Currently, in DRC, when start- ing new plantations, farmers seldom use seeds from the research centres that have guaranteed characteristics for good production. Generally, the vegeta- tive material used is from cuttings, and often, this material performs poorly.
However, the elite clones selected at Yangambi, which include seven clones of robusta (L 36, L 48, L 93, L 147, L 215, L 251, SA 158) and five clones of small Kouillou (LAF 93, LAF 159, S 9, S 19, S 23), are available, and those can be used preferentially by the farmers.
One of the priorities of the DRC government, as described in the Stra- tegic Action Plan, is the revival of the coffee production by the systematic
Clean weeding
Slashing
Pruning
Fungicide spraying
Stem paint fungicide
Control cultural practices and control methods
% infected plant
9 8 7 6 5 4 3 2 1 0
2.5 2.25 5.75
1 4
6.5
Fig. 2.7. Incidence of CWD in the robusta coffee recorded after 18 months of application of different cultural practices and control methods.
replanting of the old plantations. The government proposes to rehabilitate all the centres of production and the multiplication of the elite clones of INERA.
The plan also includes the reorganization of the supply chains of quality cof- fee material by the creation of multiplication centres and the dissemination of improved material in each of the four principal zones selected above. This will require the involvement of the Ministry of Agriculture (technical and fi- nancial support) and the ONC as partner already on the ground (Beni/Nord- Kivu and soon in Boma and Isiro).
The ONC and the farmer trade union (Syndicat pour la Défense des Inté- rêts Paysans) have set up seven centres for the multiplication of rooted cuttings at Beni, Oïcha, Irango, Bingo, Mutwanga, Vuyinga and Mayi Moya in North Kivu. The Environment and Natural Resource Accounting Company has recently acquired an in vitro propagation unit to enhance the multiplication.
2.9.3. Use of variety resistance
The production of disease-resistant coffee plants is the most desirable method of achieving control of pathogens. It appears that the coffee varieties being grown currently are very susceptible to CWD. The revival of coffee research is necessary to increase productivity and offer coffee growers the option of using high-producing vegetative material. The effort has to be undertaken to obtain new CWD-resistant clones. The research task will have to be fo- cused mainly on determining the behaviour and the level of resistance of the robusta clones (INERA elite clones and other materials introduced) towards CWD, as well as on trying to investigate the adaptation and introduction of highly productive material from foreign origins, such as clones S/2, 1S/3, 1S/6, 223/32, 257S/53 and 258S/24 from Uganda.
Researchers should also seek sources of resistance by prospecting in in- fected coffee plantations and obtaining germplasm that shows some level of natural resistance to the pathogen. Any promising material identified in the farmers’ fields will need to be multiplied and tested to ensure that this mate- rial has a good degree of tolerance or resistance.
At the University of Kinshasa, coffee research is undertaken, and the University has taken part in various projects that have contributed to the improvement of an integrated management strategy for CWD. The study about varietal resistance was carried out in natural conditions of CWD at Beni in North Kivu.
Evaluation of resistance of these accessions under natural conditions has revealed differences in reaction in these accessions. One possibility now is to operate a preselection test for genetic resistance and to clone interesting ma- terial for the evaluation of resistance in the field. A future research activity is to study the level of resistance of the seedling material taken as survivors from devastated plantations.
To date, the results obtained (based on the mortality rate recorded on differ- ent genotypes 5 mo after inoculation) have shown that a certain level of variabil- ity exists (P < 0.05) in the coffee genotypes studied for their resistance to CWD
(Table 2.1). Different groups were identified by using Tukey’s test. The materials tested were classified in four different groups: the first is composed of genotypes where the level of mortality ranged between 6.6% and 7.6%; the second, between 7.8% and 8.4%; the third, between 9% and 12.8%; and the fourth, between 13.3%
and 16.1%. Considering these different groups, the first is represented by the genotype KR 8/10, where no infection was recorded, and the fourth is repre- sented by the genotype KR 2/5, which was totally destroyed.
As part of the breeding for resistance studies, preliminary investigations were also made on the genetic diversity of the F. xylarioides population. An
Table 2.1. Varietal behaviour (percentage of mortality of inoculated plants) of different genotypes of robusta coffee tested for their CWD resistance.
No. Genotype % of Plant mortality Group
1 KR16/13A 6.6 a
2 KR19/1B 7.5 a
3 KR8/10 7.5 a
4 KR19/11 7.6 a
5 KR20/51 7.8 a b
6 KR19/18B 8.1 a b
7 KR17/55 8. 2 a b
8 KR10/7A 8.4 a b
9 KR18/10 8.49 a b
10 KR19/28 8.9 a b c
11 KR19/26 9.1 a b c
12 KR6/6 9.3 a b c
13 KR18/30 9.3 a b c
14 KR19/1A 9.5 a b c
15 KR19/55 9.7 a b c
16 KR20/50 10.2 a b c
17 KR19/31 10.3 a b c
18 KRA/6 10.6 a b c
19 KR16/55 11.0 a b c
20 KR17/47 11.2 a b c
21 KR1/3 11.2 a b c
22 KR16/13B 11.2 a b c
23 KR18/10A 11.4 a b c
24 KR1/1 11.5 a b c
25 KR19/18A 11.8 a b c
26 KR10/7B 12.1 a b c
27 KR19/12 12.3 a b c
28 KR20/31 12.4 a b c
29 KRC/3 12.5 a b c
30 KR3/5 12.6 a b c
31 KR12/6A 12.9 a b c
32 KR8/8 13.3 b c
33 KR20/10 14.4 b c
34 KR9/8 15.0 b c
35 KR2/5 16.1 b c
absence of genetic diversity within the population of F. xylarioides was re- vealed by molecular analysis using random amplified polymorphic DNA markers.
2.9.4. Sensitization of stakeholders
Extension is an essential part of management of the disease because farmers have to be informed of the results of research in order for them to be sensitized on the use of innovations. The structure of the Congolese coffee plantations must be taken into account when developing new strategies of extension and training of the farmers (e.g., the Farmer Field School approach). Financial, logistic and human means must also be taken into account, not only with the vast areas to be supervised but also, more especially, with the extent of the tasks to be achieved. Under the Common Fund for Commodities programme, ONC has conducted a training programme on CWD diagnosis and identifica- tion as well as training on management of the disease. We have initiated radio programmes in Beni and Isiro for farmers and all stakeholders, which cover all aspects of coffee production and CWD.