A Survey of Coffee Diseases in Nigeria G.A. FILANI Printed at the CRIN Internal Printing Unit and published by . Cocoa Research Institute of Nigeria Gambari Experimental Station P. M. B. 5244, Ibadan. July 1976. A SURVEY OF COFFEE DISEASES IN NIGERIA G. A. FILANI, Cocoa Research Institute of Nigeria, Ibadan ABSTRACT Coffee is cultivated over large areas of Nigeria, particularly in the Southern parts where Coffea canephora ("Robusta") is scattered over wide areas in Oyo, Ondo, Ogun, Bendel and Kwara States and in the riveraine parts of the Northern States . Coffea arabica is grown only on the Mambilla Plateau in the Gongola State where the cool weather is favourable to easy cultivation of this variety. Coffea canephora is the hardier of the two varieties and its most important diseases include the following: leaf blight or leaf scorch caused by Botryodiplodia theobromae, and the brown leaf spot caused by Cercospora coffeicola. The only berry disease observed was a pink mould identified to be a combination of Fusarium and Gloeosporium spp. Most of these occur during the dry season when the crop is subjected to water stress, and the plants quickly recover when the rains b.egin. The most important disease of Coffea arabica is the leaf rust. The Orange rust (Hemileia ·vastatrix) is more predominant on older trees in the field, while the Grey rust (Hemileia coffeicola) is more associated with seedlings in the nursery. The Brown leaf spot (Cercospora coffeicola) and the Hail-Stone damage are the other predominant leaf diseases. No incidence of Coffee Berry disease was observed during the survey. Both varieties of coffee suffer from various nursery diseases, but the most important of these are seed-decay and seedling root-rot, and the most closely associated fungi are Pythium ultimum, Rhizoctonia solani and various Fusarium spp. INTRODUCTION Coffee farms are scatered over large areas of Nigeria particularly in the Southern parts. There are many species of this crop, but broadly, the main ones cultivated are Q;_ arabi ca and h canephora or "Robusta". h canephora is grown mai nly in parts of Oyo , Ogun, Ondo, Bendel, Kwara and the riverain parts of the Northern States where the annual r ainfal l ranges from 100 - 200 em. but too hot to support the culti vation of Coffea arabica. In the Oyo , Ogun and Ondo States, approximately 87% of the coffee acreage belongs t o peasant farmers whose hol dings range from one to five acr es . The rest of the coffee is grown principally in plantati on and almost all of these are owned by the Western State Agricultural Investment Corporation (WSAIC), (Sands, 1958) . h arabica is grown only on the Mambilla Plateau of the Gongola State. Thi s Plateau lies in the Gashaka­ Mambilla Division of the Sardauna Province of the State, and it rises to a height of 1500 - 1900m . above sea level , and i t covers approximately 4000 sq. km. (Are etal 1965). The weather is cool with a mean minimum temperature of 65°F and a mean maximum of 85°F. The rainfall, 1500 - 2000mm . per annum , starts during early March and continues to the end of October. Most of the farms are owned by the individuals, and the state Ministry of Agriculture is encouraging more farmers to plant coffee by supplying seedlings at very low cost , (lK per seedling), by giving advice on proper cultural methods , and by establishing model and pilot farms. Most important to the farmers , the New Nigerian Development Corporation (NNDC) provides a ready market for good quality and ripe cherries at the favourable price of 5K per 453.6gm. · The establishment by the NNDC of small hulling and drying pl ants at key locations means that farmers no longer have to process their own coffee , and a higher and uniform grade pr oduct can therefore be obtained . • During the survey, visits were paid, at least once every t wo months and where possibl e once a month throughout the year, to various locations where coffee is grown. Di scussions were held with the farmers with regards to their problems and disease specimens were brought into the labora­ tory for routine isolations and identification. Isol ations were made from specimens by first surface sterilizing by dipping in 60% ethanol and flaming before plating on Pot atoe Dextrose Agar (PDA) . Plates were examined everyday 3 and any fungal growth was quickly subcultured onto fresh PDA with a flamed needle . Cultures that could not be identified in C.R. I.N. laboratories we're sent to· the University of Ibadan B~tany Department. Figure I shows the locations and areas covered during the survey and Table I shows the approximate acreages of Coffee grown in different parts of Nigeria, while Table II shows the major diseases of coffee in Nigeria::- · · · FOLIAGE AND BERRLDISEASES (a) Hemileia Leaf Rust The Leaf rust disease caused by Hemileia vastatrix Berk & Bri. is by far · the most seri0us disease of coffee in Nigeria and in the world as a whole. This disease had led to the ruin of many coffee industries in Ceylon, India, Java, the Philippines and other regions of the world, and it is still a limiting factor for coffee production in many countries in Africa. At present, the disease is endemic in almost all the regions where coffee is grown and even now in Brazil which has been rust- free, the disease has become ·firmly established (d10liveira, 1971, 'Wellman, 1970). ~ arabica is very susceptible to this disease, while~ canephora is generally resistant, though 'the pustules may be found on the leaves of some trees . None of the Robusta trees present in Nigeria however, has been observed to be attacked, and there are no previous records of any attack. At the 1550 acre W.S.A.I.C. farm Owo, in Ondo State, where a few stands of £..:_ arabica are. growi.ng and whi~h are heavily attacked by the orange rust, no traces ;'of leaf spots ·have been found on the £..:_ canephora. The two species of rusts - orange rust · ~ · vastatrix, and grey rust. !:!.:.. coffeicola Maubl. & Roger were found present on ~ arabica on the Mambilla Plateau. The or~nge rust which was found widespread on older trees of all the farms visited, produces yellowish-orange powdery, roundish blotches on the lower sur~ace of the leaves. When they first appear, the area affected by a single infection is about 3 - 4mm in diameter but it gradually expands until it fuses with other infeetions. In the early st.ages only a pale yellow spot on the leaf is visible but it becomes yellower as the infection progresses·:and?spo:te production ' commences. The upper surface of the leaf shows a yellow 4 area in the region of infection but the surface does not become powdery. The powdery appearance on the lower surface is due to the production of the orange · uredospores of the fungus . The grey rust found only on very few farms and on seedlings in the nurseries is different in appearance . The part of the leaf that is affected is not so clearly defined. It spreads irregularly through the leaf developing from an edge infection to all parts of the leaf. Spores occur also only on the lower leaf surface and appear as clumps of uredospores. In a severe attack of rust, the leaf surface may be completely covered with rusted areas, and as these. areas age their centres die, turn brown and dry out. This leads to heavy defoliation ·and therefore loss of yield . The Coffee Research Centre, Oeiras, Portugal, has differentiated 26 physiologic races of H. vastatrix from 1269 samples receive~ from 36 different-areas of the world including Nigeria from where races II and III have been identified (d'Oliveira, "1971) . (b) . Brown Leaf Spot This disease caused by Cercospora' ·coffeicola Back. and Cooke, attacks both varieties of Coffee and it is sometimes referred to as Cercospora Leaf Spot . It is one of the most common and yet least damaging of Coffee leaf diseases. The spots,. which are brown in colour vary in sizes from 3mm to 8mm. In some cases, particularly on the Mambilla Plateau, the spots were observed to coalesce thus resulti.ng in consi­ derabQe leaf fall. This disease was also found in one of the nurseries in Gembu and Kusuku, Mabilla and, under condi­ tions of severe infection, can lead to def~liation, die-back of seedlings which then become unfit for transplanting in the field. (c) Leaf Blight or ·Leaf Scorch - I Jfhis condition was observed ·to be most prevalent on both varieties of Coffee during the dry season. The affected leaf starts drying up from the tip which turns .dark brown. It becomes curved outwards and under severe conditions the leaf roles up completely and then drops. This spreads to other leaves and eventually the whole ·brancb is infected and becomes dried. Under very severe water stress this 5 may spread to the main trunk and the whole plant starts to die back. When the dead leaves and laterals were plated on PDA , Botryodiplodia theobromae was the frequently isolated fungus (Filani, 1972), ~ theobromae which in this case is regarded as a post- drying invader of dead tissues, is how­ ever, a ubiquitous weak pathogen which has also been found on cocoa pods (Okaisabor, 1968), and on stored nuts, leaves and roots of Cola nitida (Adebayo, 1968). Further observa­ tions made during the w;t season showed that many of the plants quickly recover, but in most cases they have to develop new laterals . (d) Pink Berry Mould In many farms, particularly in the Ogun, Oyo and Ondo States where farmers have for a very long time neglected their farms, a pink mould was found to occur on berries, particularly of light crops which have been left unharvested.