Diseases of the Oil Palm

Abstract

Thirty two diseases and disorders affecting the oil palm in Africa, Southeast Asia and South America are described with their distribution, economic importance, etiology and control. Of these, nine diseases are considered to be of major economic importance, 19 are of minor importance, and four are due to nutrient deficiencies. The major diseases causing serious economic losses are freckle (Cercospora elaeidis), blast (Pythium splendens and Rhizoctonia lamellifera), vascular wilt (Fusarium oxysporum f. sp. elaeidis). Ganoderma trunk rot (Ganoderma spp.) and Armillaria trunk rot (Armillariella mellea) in Africa; Ganoderma trunk rot, Corticium leaf rot (Corticium solani). Marasmius bunch rot (Marasmius palmivora) in S.E. Asia; sudden wilt and spear rot in S. America. Some of the diseases and disorders of minor economic importance recorded in these areas are anthracnose (Botryodiplodia palmarum, Melanconium sp. and Clomerella cingulata), dry basal rot (Ceratocystis paradoxic), patch yellows (Fusarium oxysporum), crown disease, Cylindrocladium leaf spot (Cylindrocladium macrosporum), algal spot (Cephaleuros virescens), bronze streak, ring spot and little leaf in Africa; Curvularia leaf blight (Curvularia eragrostidis), Leptosphaeria leaf spot (Pestalotiopsis spp.) infectious chlorosis, upper stem rot (Phellinus noxius), stem wet rot, charcoal base rot in S.E. Asia and Leptosphaeria leaf spot and coconut wilt disease in S. America. Little is known, however, about the disease problems in the smaller but rapidly expanding oil palm growing areas of Thailand, Papua New Guinea, India and Sri Lanka. Infectious chlorosis, bronze streak and ring spot have a suspected virus etiology; little leaf, spear rot and stem wet rot are attributed to bacteria and leaf chlorosis, mid-crown yellowing, orange frond and hook leaf to nutrient deficiencies. The etiology of some minor disorders including brown germ, crown disease and several miscellaneous abnormalities is unknown.

Effective control measures, based on the application of various chemicals, have been devised for the leaf diseases but other than precautionary cultural operations, there are no such effective and practical control measures for the root and stem diseases. For this latter group of diseases field transplanting or resistant or tolerant varieties seems to be the best method of control. Seeds selected for tolerance to vascular wilt are being produced on a commercial scale at the Nigerian Institute for Oil Palm Research, Institut de Recherches pour les Huiles et Oleagineux in Ivory Coast and the Unilever Plantations in Cameroun Republic. These efforts need to be supplemented by breeding for resistance to the other major diseases.     

Induced resistance against Fusarium diseases of <Emphasis Type="Italic">Cymbidium</Emphasis> species by weakly virulent strain HPF-1 (<Emphasis Type="Italic">Fusarium</Emphasis> sp.)

The mechanism by which Fusarium diseases of cymbidium plants are suppressed by a weakly virulent strain HPF-1 of Fusarium sp. was studied. Strain HPF-1 produced microscopic, necrotic local lesions on cymbidium leaves, causing minor damage to palisade tissues at the infection sites. This weakly virulent strain remained near the site of infection and did not develop further. It systemically and nonselectively suppressed some diseases of cymbidium such as yellow spot of leaves caused by Fusarium proliferatum and F. fractiflexum, bulb and root rot caused by F. oxysporum, and dry rot of bulbs and roots caused by F. solani. Because endogenous salicylic acid levels increased in cymbidium leaves inoculated with strain HPF-1, the mechanism of disease suppression is thought to be systemic acquired resistance.     

Charcoal rot in common bean with special reference to Kenya

Abstract

Charcoal rot caused by Macrophomina phaseolina (Deuteromycetes: Coelomycetes) is found throughout the tropics and subtropics and has a wide host range. Together with most of the legume crops, the common bean (Phaseolus vulgaris) Is a good host for the fungus which causes a range of symptoms, depending on environmental conditions and age of the plant. In addition to charcoal rot, which is a stem or stalk rot disease, the pathogen also causes damping‐off and seedling blight in beans. Charcoal rot in the mature plant is associated with senescence which is accelerated by water stress. The disease is most damaging in areas of unreliable rainfall and high temperature. In Kenya, beans are usually grown in mixed stands with maize, sorghum or millet. Population pressure has led to the cultivation of beans on land prone to drought. M. phaseolina is one of the most important pathogens affecting all the main crops of the farming systems in the semi‐arid areas of eastern Kenya and resistance to charcoal rot is a priority if beans are to be increasingly grown in these areas. The paper reviews the literature on charcoal rot of beans and on other crops where similar work has not been reported specifically for beans.     

Epidemiology of Fusarium Diseases and their Mycotoxins in Maize Ears

Fusarium species cause two distinct diseases on ears of maize, Fusarium ear rot (or pink ear rot) and Gibberella ear rot (or red ear rot), both of which can result in mycotoxin contamination of maize grain. The primary causal agent for Fusarium ear rot is Fusarium verticillioides, but F. subglutinans and F. proliferatum are also important. Gibberella ear rot is caused primarily by F. graminearum, but F. culmorum can also be important, especially in Europe. Aspects of the epidemiology of both diseases have been studied for decades, but only recently have efforts been made to synthesize this information into comprehensive models of disease development. Much of the work on F. graminearum has focused on Fusarium head blight of small-grain crops, but some of the results obtained are also relevant to maize. The primary mycotoxins produced by these fungi, fumonisins and deoxynivalenol, have differing roles in the disease-cycle, and these roles are not completely understood, especially in the case of fumonisins. Progress is being made toward accurate models for risk assessment of both diseases, but key challenges remain in terms of integrating models of pre- and post-infection events, quantifying the roles of insects in these diseases, and characterizing interactions among competing fungi and the environment.     

黄淮海夏玉米主产区穗腐病病原菌的分离鉴定

为明确我国黄淮海夏玉米主产区玉米穗腐病的病原菌种类、优势种群及虫害、年度、省份对病原菌的影响,以形态学为基础,结合分子生物学方法对2013、2015年随机采自河南、河北、山东3省的155份玉米穗腐病样品进行分离鉴定。结果表明,引起黄淮海夏玉米主产区玉米穗腐病的主要致病菌为镰孢菌Fusarium spp.,包括拟轮枝镰孢F.verticillioides、禾谷镰孢F.graminearum、层出镰孢F.proliferatum、木贼镰孢F.equiseti及藤仓镰孢F.fujikuroi,分离频率分别为49.7%、28.4%、12.3%、3.9%和1.3%;其次为木霉菌Trichoderma spp.,包括哈茨木霉T.harzianum、绿色木霉T.viride和棘孢木霉T.asperellum,分离频率分别为8.4%、3.2%和5.2%;青霉菌Penicillium spp.分离频率较低,为14.2%;曲霉菌Aspergillus spp.包括黑曲霉A.niger和黄曲霉A.flavus,分离频率分别为2.6%和1.9%。研究表明,黄淮海主产区玉米穗腐病优势病原菌为拟轮枝镰孢、禾谷镰孢和木霉菌,不同省份不同年度间病原菌种类及优势病原菌存在差异,虫害能加重玉米穗腐病的发生。     

A survey of rice diseases in Bangladesh

Abstract

A survey conducted during 1979–81 in Bangladesh revealed 20 rice diseases, including two viral, two bacterial, 13 fungal, two nematode and one micronutrient deficiency problem. Of these diseases. 16 appeared as major during the period under report. The number of diseases were 17, 16 and 16 during the Boro. Aus and transplant Aman seasons, respectively, with 12 common in all three seasons. Thirteen diseases including bacterial blight, bacterial leaf streak, sheath blight, sheath rot, blast, brown spot, grain spot, stem rot and leaf scald were classified as major; and tungro, bakanae, cercospora leaf spot and zinc‐deficiency were classified as either major or minor, and were common to all regions. Diseases not common in all regions were stack burn, root knot, and ufra classified as major or minor, and false smut, seedling blight. Yellow dwarf and damping off which were always classified as minor. Diseases which were typical for Boro. Aus and transplant Aman seasons were seedling blight and damping off. Yellow dwarf, and false smut respectively. Aus the most humid and warmest season, and the coastal humid areas experienced more major diseases. Seasonal and regional differences in the disease incidence appeared related to agro‐climatic variations.     

Phytophthora species attacking strawberry and raspberry1

Phytophthora frugariae causes red core root rot of strawberries. Although the disease is probably most acute in northern Europe, serious outbreaks have been reported from a number of Mediterranean countries, especially France and Italy. Leather rot of fruit and crown rot, which are caused by P. cuctorum, can also be severe problems in warmer climates. Both fungi survive in soil for long periods, but the most common form of spread is in diseased planting material. Sensitive tests have been developed to detect red core in planting material, and been used to effect in certification schemes. Root rot of raspberry has gained prominence in the last 10 years in Europe as raspberry growing has expanded, but the disease has been known for many years in France. Nine species of Phyfophthora have been recovered from affected plants, but two of these, one with affinities with P. megasperma, and P. cumbiuora, are responsible for most major outbreaks. The other species are only troublesome where drainage is poor. Again, spread is mainly in infected material. Few raspberries are resistant to root rot, but some wild RubuP spp., blackberries and raspberry x blackberry hybrids are resistant and may be useful in breeding programmes.     

Molecular identification and pathogenicity of Fusarium and Alternaria species associated with root rot disease of wolfberry in Gansu and Ningxia provinces,China

Wolfberry (Lycium barbarum) ranks in the top 10 best-selling medicinal plants in China and it has been used for centuries as a medicine and a food supplement. It is suggested to have benefits on human health due to the rich content of polysaccharides, carotenoids, flavonoids, and alkaloids contained in its fruits, leaves, and root bark. Recently, severe root rot diseases have been causing plant losses in major growing areas. Here, we report fungi causing root rot disease in Chinese wolfberry plants. The analysis of nucleotide sequences of the internal transcribed spacer (ITS) region revealed a total of 92 isolates isolated from both soil and plant material samples. Fusarium spp. were the most abundant (58%), followed by Penicillium spp. (9%), and Alternaria spp. (5%). Fusarium spp. included F. oxysporum (36%), F. solani (30%), F. chlamydosporum (9%), F. nematophilum (9%), and F. tricinctum (8%). Sequences from the translation elongation factor 1-α gene (TEF-1α) were used to confirm the identity of Fusarium spp. and showed the predominance of F. oxysporum and F. solani. To confirm the pathogenicity of isolates, four isolates belonging to Fusarium spp. and one isolate belonging to Alternaria spp., isolated from wolfberry root tissues with root rot symptoms, were tested in outdoor and laboratory conditions. Results revealed that the five tested isolates were pathogenic with varying degrees of aggressiveness and ability to induce symptoms of root rot in wolfberry seedlings. The five isolates were recovered from inoculated seedlings, completing Koch's postulates. This is the first report on causative agents of root rot in Chinese wolfberry.     

Characterization of isolates of binucleate Rhizoctonia spp. associated with strawberry black root rot complex using fatty acid methyl ester (FAME) profiles

Black root rot is an important disease of strawberry caused by a complex of fungi that includes species of Rhizoctonia. In this study, a modified MIDI method (Microbial Identification System) was investigated for its utility to differentiate isolates of the three different anastomosis groups (AGs) of binucleate Rhizoctonia spp., associated with strawberry black root rot complex representing AG-A, AG-G, and AG-I. A total of 11 fatty acids were detected, and the FAME profiles for isolates of the three different AGs of Rhizoctonia spp. varied quantitatively and qualitatively. Moreover, the modified MIDI method will be a useful discriminatory tool for fungal identification and classification of the AGs of binucleate Rhizoctonia spp. associated with strawberry black root rot complex.     

Influence of Climatic Factors on Fusarium Species Pathogenic to Cereals

Fusarium head blight of small-grain cereals, ear rot of maize, seedling blight and foot rot of cereals are important diseases throughout the world. Fusarium graminearum, F. culmorum, F. poae, F. avenaceum and Microdochium nivale (formerly known as F. nivale) predominantly cause Fusarium diseases of small-grain cereals. Maize is predominantly attacked by F. graminearum, F. moniliforme, F. proliferatum and F. subglutinans. These species differ in their climatic distribution and in the optimum climatic conditions required for their persistence. This review deals with the influence of climate on the production and dispersal of inocula, growth, competition, mycotoxin production and pathogenicity. Most species produce inocula, grow best, and are most pathogenic to cereal heads at warm temperatures and under humid conditions. However, the optimal conditions for F. moniliforme and F. proliferatum maize ear rot tend to be hot and dry and M. nivale head blight, seedling blight and foot rot of small-grain cereals tend to occur under cooler conditions. Seedling blight and foot rot caused by other species are favoured by warm dry weather. Between them, these fungi produce four important classes of mycotoxins: trichothecenes, zearalenone, fumonisins and moniliformin. Conditions favourable for in vitro growth are also generally the most favourable for mycotoxin production on cereal grains. These fungi rarely exist in isolation, but occur as a complex with each other and with other Fusaria and other fungal genera. Climatic conditions will influence competition between, and the predominance of, different fungi within this complex.     

Targets for pathology research in protected crops

Due to the need to diminish the amount of pesticides used, alternative ways of controlling fungal diseases have to be developed. Foliar diseases have been managed mainly by chemicals, but research has been started to develop integrated control programmes. Data from studies on epidemiology, in combination with nutritional and climatic management and use of partial resistant cultivars will lead to a reduced use of chemicals. Models used are: Botrytis cinerea in gerbera and roses, and powdery mildew in roses and cucumbers. Research has been intensified on biological control of these pathogens. In closed systems, with recirculation of the nutrient solution, soil-borne fungi can cause serious problems. Not only do diseases known from traditional cultural systems, like fusarium wilt of carnation, fusarium crown and root rot of tomato and Phytophthora and Pythium spp. in several crops occur, but also new problems like a new Phytophthora sp. and Gnomonia sp. in roses and a Cylindrocladium sp. in Spathiphyllum spp. To prevent introduction of pathogens in recirculation systems, emphasis is put on developing an integrated disease management programme by using disease-free planting material, disease-free irrigation water, strict hygienic measures, resistant cultivars, methods of disinfecting the nutrient solution and biological control. Research over the last 5–6 years has revealed good prospects for biological control, especially in closed systems with a limited amount of substrate. Wilt in carnation, caused by Fusarium oxysporum f.sp. dianthi can be prevented effectively by adding a non-pathogenic isolate of F. oxysporum and/or Pseudomonas spp. There are indications that non-pathogenic isolates of F. oxysporum are also effective against wilt disease in other crops. An isolate of Trichoderma harzianum appears to be very effective against fusarium crown and root rot of tomato. More applications of this, and other, biocontrol agents seem possible. However, translation of the results of research to practical application and registration is still very difficult.     

Durability of resistance in lily to basal rot: evaluation of virulence and aggressiveness among isolates ofFusarium oxysporum f. sp.lilii

Prospects of durability of resistance in lily to basal rot have been evaluated by testing the virulence and aggressiveness of 31 isolates ofFusarium oxysporum f. sp.lilii towards a number of different resistance sources inLilium spp. Isolates differed strongly in aggressiveness as did species and cultivars ofLilium spp. in resistance. Significant interactions were observed between isolates of the pathogen and genotypes ofLilium spp., but the magnitude was very small compared to the main effects. The interactions were mainly due to a small group of isolates with low aggressiveness. It is argued that the interactions might be based on minor genes. No major break down of the resistance was found. For practical purposes it will be sufficient to use highly aggressive isolates in screening tests.     

Burkholderia gladioli associated with symptoms of bacterial grain rot and leaf-sheath browning of rice plants

Rice plants with bacterial leaf-sheath browning and grain rot were observed in Fukuoka Prefecture in Japan during the autumn seasons of 1995 and 1996. Burkholderia spp. were consistently isolated from the infected leaf sheaths and grains. These isolates were pathogenic and induced symptoms of seedling rot, grain rot, and leaf-sheath browning in rice plants, as well as in some orchidaceous plants (cymbidium, dendrobium, and oncidium leaves), gladiolus leaves, and onion bulbs. On the basis of morphological, physiological and pathological tests, and species-specific polymerase chain reaction, the isolates were identified as belonging to either Burkholderia glumae or Burkholderia gladioli. B. gladioli, as well as B. glumae, attacked rice plants after artificial inoculation and reproduced the symptoms similar to those after natural infections. We confirmed that rice is an additional natural host of B. gladioli. It is clarified that bacterial grain rot of rice is caused not only by B. glumae but also by B. gladioli.     

Population dynamics of Rhizoctonia,Oculimacula, and Microdochium species in soil,roots, and stems of English wheat crops

This study aimed to elucidate the population dynamics of Rhizoctonia, Oculimacula, and Microdochium species, causing the stem base disease complex of sharp eyespot, eyespot, and brown foot rot in cereals. Pathogen DNA in soil, roots, and stem fractions, and disease expression were quantified in 102 English wheat fields in two seasons. Weather data for each site was collected to determine patterns that correlate with assessed diseases. Oculimacula spp. (66%) and R. solani AG 2-1 (63%) were most frequently detected in soil, followed by R. cerealis (54%) and Microdochium spp. (33%). Oculimacula spp. (89%) and R. cerealis (56%) predominated on roots and soil but were not associated with root rot symptoms, suggesting that these species used soil and roots for survival and as inoculum source. M. nivale was more frequently detected than M. majus on stems up to GS 21–30 and co-occurred on plant samples with O. acuformis. O. yallundae had higher DNA concentration than O. acuformis at the lower 5 cm basal region at GS 37–45. R. cerealis predominated in the upper 15 cm above the base beyond stem extension. Brown foot rot by Microdochium spp. was favoured by cool and wet autumns/winters and dominated in English wheat. Eyespot and sharp eyespot disease index by Oculimacula spp. and R. cerealis, respectively, correlated with wet/humid springs and summers. Results suggested that stem base pathogens generally coexisted; however, their abundance in time and space was influenced by favourable weather patterns and host development, with niche differentiation after stem extension.     

Distribution and virulence of fungal species isolated from yam (Dioscorea spp.) tubers in three agroecological zones of Nigeria

Abstract

Field surveys were conducted in 2012 and 2013 to evaluate the distribution and virulence of fungal isolates associated with tuber rot disease among yam (Dioscorea spp.) producing agroecological zones (AEZs) of Nigeria. A total of 70 and 66 farmers’ fields were surveyed in 2012 and 2013, respectively among three yam species, Dioscorea rotundata, D. alata and D. cayenensis. Fifteen rotted samples were randomly collected per each yam species in fourteen districts across the humid rainforest (HF), the derived savanna (DS) and the southern Guinea savanna (SGS) agroecologies. Twenty-one fungal species were isolated in the HF, 18 species in the DS and 16 in the SGS. The highest rot severity was in HF agroecology in the D. rotundata which varied from 27.2% to 65.7% in 2012 and from 21.1 to 57.4% in 2013, while the SGS agroecology had the least severity. Lasiodiplodia theobromae was the most virulent pathogen with lesion diameter of 26.8–42.1?mm at 14?days after inoculation. Findings provide baseline information for the formulation of management strategies for yam tuber rot disease in Nigeria.     

Characterization of Lasiodiplodia species causing leaf blight,stem rot and fruit rot of fig (Ficus carica) in Malaysia

Fig (Ficus carica) is an exotic deciduous plant that is grown worldwide. Fungal diseases pose a major threat to fig plants, affecting their fruit quality and production. This study was conducted to characterize the fungal isolates associated with leaf blight, stem rot and fruit rot of F. carica in Malaysia through morphological analysis, DNA sequencing, multigene phylogenetic analysis and pathogenicity tests. From September 2018 to March 2019, 30 blighted leaves and 30 rotted stems and fruits of F. carica were collected from several nurseries in Malaysia. Thirty fungal isolates that belonged to Lasiodiplodia theobromae (27 isolates) and L. brasiliensis (three isolates) were identified based on morphological characteristics, comparison of DNA sequences and phylogenetic analysis of the internal transcribed spacer (ITS), elongation translation factor 1-α (tef1-α), β-tubulin (tub2) and DNA-directed RNA polymerase II subunit (rpb2). Among the 27 isolates of L. theobromae, nine isolates were obtained from leaves, eight isolates from stems and 10 isolates from fruits, whereas the three isolates of L. brasiliensis were obtained from stems (two isolates) and a leaf (one isolate). The results of pathogenicity tests revealed that L. theobromae and L. brasiliensis isolates were responsible for leaf blight and stem rot of F. carica, whereas fruit rot was caused by L. theobromae isolates. The present study highlighted two different species, L. theobromae and L. brasiliensis, as the causal agents of leaf blight and stem rot of F. carica. Additionally, L. theobromae caused fruit rot of F. carica in Malaysia.     

Identification and pathogenicity of Fusarium species associated with pokkah boeng of sugarcane in Brazil

Brazil is the world’s biggest producer of sugarcane (Saccharum spp. hybrids). Pokkah boeng is an important fungal disease in this crop caused by members of the Fusarium fujikuroi species complex (FFSC) and characterized by deformation of the aerial part of the plant and stem rot. While the occurrence of symptoms has been reported in plantations in Brazil, no official reports of the disease exist. In this study, species of the FFSC were identified that are associated with sugarcane plants with symptoms of pokkah boeng in Brazil. This was achieved using two-loci molecular phylogeny, sexual compatibility and analysis of morphological markers. The ability of strains to cause disease in plants of sugarcane, maize, sorghum and millet was also evaluated. The 39 isolates studied were identified as F. sacchari, F. proliferatum and another, still unknown, phylogenetic lineage that is sister to F. andiyazi. Crossing field isolates of F. sacchari and F. proliferatum with their respective tester strains produced fertile perithecia and viable ascospores. All three species induced symptoms of pokkah boeng on inoculated sugarcane plants and caused stem rot in maize, sorghum and millet. Symptoms on sugarcane are chlorosis and necrosis of leaves, punctured lesions, twisted leaves, reduction of the total leaf area, death of the top of the plant and stalk rot. The findings confirmed the aetiology of the disease in Brazil, generated basic knowledge for the development of strategies for diagnosis and monitoring of the disease and support breeding programmes for selecting resistant germplasm.     

Foot Rot of Ulluco Caused by Pythium aphanidermatum

Severe rot of stem bases caused by Pythium aphanidermatum was found on ulluco (Ullucus tuberosus) grown in Kagawa Prefecture, Japan, in September 1999. The name “foot rot of ulluco” is proposed for this new disease. Received 14 November 2001/ Accepted in revised form 7 January 2002     

Development and implementation of cost-effective strategies to manage brown rot of peach trees in Imathia,Greece

Development of cost-effective strategies to manage brown rot caused by Monilinia laxa of peach implies a better understanding of the susceptibility of different cultivars and pre-harvest contamination. This study investigated the susceptibility of 24 peach and nectarine cultivars to shoot blight caused by Monilinia spp. and found various levels of susceptibility, with the nectarine cultivar Tasty Free scored as the most susceptible. Studies on the the existence and detection of latent infections by Monilinia spp. in three peach (‘A37’, ‘Andross’, and ‘E-45’) and three nectarine (‘Venus’, ‘Fantasia’, and ‘Tasty Free’) cultivars were also conducted. The results showed that latent infections were detected only in nectarine cultivars when fruit were collected on 23 May and 22 June. In contrast, nectarine fruit collected on 7 June and all peach cultivars tested had no detectable latent infection. This study also indicated that the fungicide thiophanate methyl applied at the pit hardening stage reduced significantly the percentage of latent infection and subsequently preharvest fruit rots. Finally, a disease forecast model to predict blossom blight, caused by M. laxa, was evaluated in the Prefecture of Imathia, Greece. Trees, sprayed according to the model predictions, showed a statistically lower percentage of blighted shoots than those of unsprayed trees.     

Root rot of hyacinths caused by species of Pythium

The root rot widely seen in hyacinth was found to be caused byPythium spp. instead of byFusarium culmorum. Of sixPythium species isolated, three, includedP. ultimum andP. violae, were investigated in glasshouse experiments and their pathogenicity demonstrated. In these experiments plants were successfully grown in containers in which an aqueous mist was maintained, or in water cultures. In experimental plots on infected soil, Dexon, a fungicide selective for Pythiaceae, distinctly reduced the number of dead plants and increased yield and bulb size, thus confirming the role ofPythium in causing root rot. Practical application of Dexon deserves further attention.