Fruit Spot Disease Research Articles

Reaction of Selected Citrus Cultivars to Pseudocercospora Leaf and Fruit Spot Disease Under Natural Infection in Northern Uganda

Citrus is an important crop among many resource constrained subsistence farmers living in rural areas of Uganda. Citrus production is affected mainly by drought, declining soil fertility, pests and diseases. Among diseases, citrus leaf and fruit spot disease caused by fungus Pseudocercospora angolensis is currently one of the major constraints to the production of citrus in Uganda where millions of people rely on the crop for nutritional security and household income. The disease can lead to 50-100% fruit yield loss depending on environmental conditions, disease management and weather conditions. In order to identify resistance to P. angolensis, a study was conducted to identify variability for citrus leaf and fruit spot resistance from adapted commercial cultivars as an initial step in developing integrated disease management strategy. Six cultivars were assessed. The screening was under natural infection conditions in disease hot spots in northern Uganda in 2014a and 2014b seasons. The results showed significance difference (p < 0.01) for Area Under Disease Progressive Curve (AUDPC) for number of leaves with P. angolesnis symptoms and number of lesions. Subsequently, the study identified Kuno as resistant and Tangelo as less susceptible to Pseudocercospora leaf and fruit spot infection, and they could be recommended for citrus leaf and fruit spot disease control.

Re-Fining Citrus Leaf and Fruit Spot Disease Control Options in Northern Uganda

Citrus leaf and fruit spot disease, caused by Pseudocercospora angolensis has, since 2010, come about as the most dreadful disease of citrus in Northern Uganda. Over the last few years, feedback from citrus farmers has helped in re-fining management strategies. In the first years of citrus leaf and fruit spot disease outbreak in Northern Uganda, chemical treatment was promoted as part of a control package, in addition to the destruction of heavily diseased plants and buckthorn to remove inoculum. Buck horning and destruction of diseased plants is labour-intensive and time-consuming, especially when many infected citrus trees have to be taken out, or buck horned. Research findings indicate citrus leaf and fruit spot disease fungus can be weakened with fungicide sprays to the extent that even when disease symptoms are present on leaves, it does not automatically lead to infection of fruits. This gave rise to a new control strategy where only infected plants in an orchard are pruned, and all the citrus trees in the orchard are treated with fungicides. The pruning of visibly infected plants in an orchard will lessen the inoculum load, and the fungicide sprays will stop pathogen replication. This method is not labour intensive and takes less time when equated to severe buck horning of all the trees in the orchard. However, pruning and fungicide treatment need to move together with the control of new infections that can happen via unrestricted entry during harvesting

A CRISPR/LbCas12a-based method for detection of bacterial fruit blotch pathogens in watermelon.

Acidovorax citrulli is the main pathogen causing bacterial fruit blotch, which seriously threatens the global watermelon industry. At present, rapid, sensitive, and low-cost detection methods are urgently needed. The established CRISPR/LbCas12a visual detection method can specifically detect A. citrulli and does not cross-react with other pathogenic bacteria such as Erwinia tracheiphila, Pseudomonas syringae, and Xanthomonas campestris. The sensitivity of this method for genomic DNA detection is as low as 0.7 copies/μL, which is higher than conventional PCR and real-time PCR. In addition, this method only takes 2.5 h from DNA extraction to quantitative detection and does not require complex operation and sample treatment. Additionally, the technique was applied to test real watermelon seed samples for A. citrulli, and the results were contrasted with those of real-time fluorescence quantitative PCR and conventional PCR. The high sensitivity and specificity have broad application prospects in the rapid detection of bacterial fruit blotch bacterial pathogens of watermelon.IMPORTANCEBacterial fruit blotch, Acidovorax citrulli, is an important seed-borne bacterial disease of watermelon, melon, and other cucurbits. The lack of rapid, sensitive, and reliable pathogen detection methods has hampered research on fruit spot disease prevention and control. Here, we demonstrate the CRISPR/Cas12a system to analyze aspects of the specificity and sensitivity of A. citrulli and to test actual watermelon seed samples. The results showed that the CRISPR/Cas12a-based free-amplification method for detecting bacterial fruit blotch pathogens of watermelons was specific for A. citrulli target genes and 100-fold more sensitive than conventional PCR with quantitative real-time PCR. This method provides a new technical tool for the detection of A. citrulli.

Spatial Distribution of Citrus Pseudocercospora Leaf and Fruit Spot Disease and Shade Effect on Disease Intensity

Adapting agricultural systems to face persistent environmental hazards is at the center of global concerns. In line with this, understanding and highlighting the structural characteristics of agroforestry systems could strengthen their resilience in terms of disease management. This study was conducted to evaluate the effect of shade on the intensity of citrus leaf and fruit spot disease caused by Pseudocercospora (PLFSD). Investigations to assess the effects of shade components on the incidence of PLFSD were carried out on 15-year-old tangerine trees in a cocoa-based agroforestry plot (Bokito) during four fruits seasons. Tangerines under the shade of large forest trees were compared to others located under full sunlight. A complementary experiment was conducted on young grapefruit plants in an orchard with mango and avocado groves in Foumbot. Three shading conditions, i.e., under avocado trees, under mango trees, and without shade, were explored. Data on shade and PLFSD incidence were collected and analyzed. Our findings show that PLFSD incidence was null on tangerine leaves from trees under shade compared to those under full sunlight. The same trends were observed in fruits under shade and under full sunlight. Disease incidence on grapefruit leaves was lower on trees under shade compared to those under full sunlight. In short, shade trees appear to constitute potential physical barriers to disease progression. This study also highlights disease spatial distribution as beyond 12 m of distance between neighboring trees, no spatial dependence of disease spread was observed. Management actions based on the distance between citrus trees and regulating shade are envisaged.

Evaluation of Fungicides for Effective Management of Leaf and Fruit Spot (<i>Pseudocercospora angolensis</i>) Disease of Citrus under Field Conditions

Leaf and fruit spot (Pseudocercospora angolensis) disease of citrus attacks leaves, fruits, and young twigs of the plant. The disease can cause a yield loss of (50% to 100%) in areas with high rainfall and humidity during the active growth stages of the crop. Currently, citrus plantations in the south, south-west and north-west of Ethiopia are seriously affected by this disease. As a result, this study was proposed to study the effect of fungicides in controlling. And candidate fungicides were: Carbonchlor 50% SC only, Benline 50% WP only, Bellis 38% WG only, Carbonchlor 50% SC combined with Bellis 38% WG, Benline 50% WP combined with Carbonchlor 50% SC and Benline 50% WP combined with Matco 72% WP for effective management of citrus leaf and fruit spot (Pseudocercospra angolensis) disease. The study was carried out in 2021 cropping season. A Randomized Complete Block Design (RCBD) with three replications was the design applied. The result showed that the highest level of efficacy (90.46%) was produced by Bellis 38% WG fungicide followed by Carbonchlor 50% SC (86.50%), Bellis 38% WG + Carbonchlor 50% SC (82.00%), Carbonchlor 50% SC + Benline 50% WP (67.89%), Benline 50% WP (65.62%) and Matco 72% WP + Benline 50% WP (49.48%). Therefore, based on the outcome of the study application of Bellis 38% WG only followed by Carbonchlor 50% SC only, Carbonchlor 50% SC combined with Benline 50% WP, Bellis 38% WG combined with Carbonchlor 50% SC, Bellis 38% WG only, Benline 50% WP only and Matco 72% WP combined with Benline 50% WP were effective fungicides to be used for the control of leaf and fruit spot disease.

Distribution and Status of Citrus Leaf and Fruit Spot (<i>Pseudocercospora angolensis</i>) Disease in North Western Ethiopia

Citrus leaf and fruit spot incited by Pseudocercospora angolensis are one of the most serious production constraints of citrus production in North Western Ethiopia. Disease survey in 10 major citrus growing districts of North-Western Ethiopia was conducted, to indicate the importance of citrus leaf and fruit spot disease and its association with agro-ecological factors. The study was carried out during 2021 and 2022 cropping seasons. And in each cropping season based on availability, a total of 280 citrus trees (200 sweet oranges, 40 mandarins, and 40 lemons) in 20 orchards were randomly assessed. This study result showed that in most of the surveyed areas, leaf and fruit spot were the most prevalent and long-lasting disease of citrus. That is, among 10 studied districts in 8 of them (100%) disease prevalence, (87.25%) incidence and (24.43%) severity were computed. As a result, most citrus growers were practiced uprooting of their citrus trees and replacing them by other fruit crops (Mango and Avocado). Therefore, from the result of the present investigation to provide sustainable citrus fruit productivity and production in areas where citrus leaf and fruit spot disease is predominant and causes a devastating effect, integrated and sustainable citrus leaf and fruit spot disease management practices should be executed. Furthermore, in order to get full illustrates of the importance of the disease, it is useful to conduct related disease surveys in major citrus growing areas of the country.

First report on black spot disease of Phyllanthus emblica L. fruits caused by Thielaviopsis paradoxa in Bangladesh

Fruit spot disease of Phyllanthus emblica L. is one of theproblems, which reduce the quality of the fruits at pre-harvest period. Fungal pathogen was isolated using tissue planting methods during November 2016 to December 2017. The fungus, Thielaviopsis paradoxa was identified using both morphological and molecular characterization based on internal transcribe spacer (ITS) region of ribosomal DNA (rDNA). Mycelial growth of the isolated fungus was evaluated on six different fungal culture media viz, potato sucrose agar (PSA), Richard agar (RA), carrot agar (CA), potato dextrose agar (PDA), honey peptone agar (HPA) and Hansen’s agar (HA) in which RA and HPA media provided the utmost growth. The optimum temperature of the fungus was recorded at 25 to 35ºC. Alternate cycle of 12h/12h light dark and neutral to basic pH was preferred by the studied fungus. Aqueous crude extracts of three plants (garlic, black cumin, and turmeric) were evaluated against the isolated fungus in which the highest inhibition was recorded due to garlic extract. Two food preservatives (sodium benzoate and vinegar) were also tested in which sodium benzoate (100 mM) was most efficient for the inhibition of T. paradoxa. Therefore, garlic and food preservative-sodium benzoate could be used to control this fungal growth associated with amla fruits. To the best of our knowledge, occurrence of T. paradoxa on amla fruits is a new record in Bangladesh.
 Int. J. Agril. Res. Innov. Tech. 10(2): 38-46, December 2020

Management of Citrus Leaf and Fruit Spot (<i>Pseudcercospora angolensis</i>) Disease Using Fungicides

In Tropical Africa, particularly Sub-Saharan Africa production of citrus is seriously hampered by citrus leaf and fruit spot (<i>Pseudocercospora angolensis</i>) disease. The yield reduction due to this disease can reach 50% - 100% when climatic conditions are favorable to the disease development and effective control measures are not implemented timely. Hence, this study was anticipated to evaluate the effect of fungicides for the management of citrus leaf and fruit spot disease. As the result of this, the efficacy of different fungicides namely; Carbonchlor 50% SC only, Benline 50% WP only, Bellis 38% WG only, Carbonchlor 50% SC combined with Bellis 38% WG, Benline 50% WP combined with Carbonchlor 50% SC and Benline 50% WP combined with Matco 72% WP against Pseudocercospra angolensis were tested under field conditions. The present field experiment result showed that, there was no infected fruit observed in all treated trees as compared to the control plot that revealed (33.12%) fruit infection. Whereas, in leaves minimum infection rate (1.16%) was recorded from trees treated with Bellis 38% WG followed by Carbonchlor 50% SC (1.48%), Carbonchlor 50% SC combined with Bellis 38% WG (1.89%), Benline 50% WP combined with Carbonchlor 50% SC (4.00%), Benline 50% WP (4.54%) and Matco 72% WP combined with Benline 50%WP (6.24%). However, maximum infection rate (17.57%) was recorded from leaves of unsprayed check. Therefore, from the results of the present investigation, application of Carbonchlor 50% SC was the first choice to be used followed by Carbonchlor 50% SC + Benline 50% WP, Bellis 38% WG + Carbonchlor 50% SC, Bellis 38% WG only, Benline 50% WP only and Matco 72% WP + Benline 50% WP for the management of citrus leaf and fruit spot disease.

Development of specific culture media, studies on effect of media, pH and temperature on growth of Cercospora punicae, the causal agent of fruit and leaf spot disease of pomegranate

The mycelail growth of Cercospora punicae on PDA is very slow therefore the present investigation describes the effects of media, pH, temperature and standardized the best media for qucik growth of Cercospora punicae (leaf and fruit spot disease of pomegranate) in vitro. Five media, Potato Dextrose Agar (PDA), Czapeck Dox Agar (CDA), Green Pomegranate Leaf Decoction Agar 5% (GPLDA), Oat Meal Agar (OMA) and Vegetable Juice Agar (V-8JA) were evaluated for their effects on growth of the pathogen. Green Pomegranate Leaf Decoction Agar medium 5% (57.50 mm) was found to support maximum mycelail growth of fungus in vitro. Therefore, five different concentrations (5; 10; 15; 20; 25%) of Green Pomegranate Leaf Extract in Potato Dextrose Agar were evaluated for standardization of optimum concentration of leaf extract for getting maximum growth of Cercospora punicae in minimum possible time. The maximum radial growth of C. punicae (90 mm) was attained at 15 per cent Green Pomegranate Leaf Decoction Agar medium in 18 days and standardized as specific medium for conducting all the laboratory studies. The maximum growth was observed at temperature levels 25 oC (89.85 mm) which was significantly superior to all other temperatures levels viz., 15, 20, 30 and 35 0C on GPLDA medium. The pathogen grew best on pH 6 and the least growth occurred at pH 4.

Distribution of Pseudocercospora fruit and leaf spot, Phytophthora foot rot and scab diseases and their effect on Citrus tree decline prevalence in the humid zones of Cameroon

Introduction – Declining Citrus trees (CTD) is a major constraint causing Citrus production depletion in Cameroon. It has been established that some pests and diseases are the major sources of that phenomenon. Improving knowledge of the contributing factors to the occurrence of CTD is key to the control of this. Materials and methods – A study based on the presence of fungal diseases caused by Pseudocercospora angolensis, Elsinoe spp., and Phytophthora spp., was carried out in 39 sites of Citrus producing basins of Cameroon. The aim of the study was to determine environmental factors favouring CTD occurrence in an effort to reducing their devastating effects on three common species of Citrus. Disease symptoms were noticed by examining tree's organs (leaves, fruits, branches, trunk). A regression analysis was applied with the General Linear Model to select the main factors involved in CTD development. The prevalence of CTD was treated as dependent variable. Independent variables were Citrus species, soil texture, vegetation, rainfall, temperature, relative humidity, altitude, observation year, prevalence of PLFSD, Citrus scab and Phytophthora diseases. Results and discussion – CTD was found in all the sites, with a mean prevalence of 25%. Citrus species, soil texture, vegetation, rainfall, Pseudocercospora fruit spot disease, scab, and Phytophthora foot rot disease were the main factors associated with CTD prevalence. Conclusion – The importance of CTD was confirmed. It has been shown that PLFSD and Phytophthora diseases were much more likely to contribute to tree decline contrary to Citrus scab. However, further analysis could pave the way for the development of a risk assessment model for CTD.

Tolerance of citrus genotypes towards Pseudocercospora leaf and fruit spot disease in western highlands zone of Cameroon

Pseudocercospora leaf and fruit spot disease (PLFSD) is a serious production constraint to citrus growers in Africa and Yemen. An assessment of the disease was carried out in the location of Foumbot, western highlands of Cameroon characterised by monomodal rainfall patterns, low temperatures and high relative humidity. The plot was set up in a complete randomised block design with eight replicates, with each comprising one stand of the 15 genotypes. The assessment was carried out in 2016, on 15 genotypes plot established in 2002, and was based on the disease impact on leaves and fruits. The impact of the disease was recorded on a scale of one to five, where one represented organ with 0% disease, and five the organs with more than 75%. Vegetative development of citrus tree attributes such as tree height, canopy mean diameter, scion and rootstock circumference were also recorded. Results showed that six genotypes presented the lowest disease severity. These are: Bearss Lime (1.75 ± 0.50), Obala Tangerine (2.00 ± 0.0), Sans Epines Lime (2.00 ± 0.53), Ponkan Yoshida (2.13 ± 0.35), Emperor Tangerine (2.43 ± 0.78) and Beauty Tangerine (2.57 ± 0.78). Ponkan Yoshida and Sans Epines Lime, that also presented the best morphological parameters, can be qualified as best candidates for their tolerance to PLFSD under these ecological conditions. Despite their morphological and tolerance to PLFSD, Bearss Lime showed 50% dead stands. Further investigations on opportune pests and diseases affecting citrus should be carried out to assess their contribution on these, on similar ecological environment.

Genera Acremonium and Sarocladium Cause Brown Spot on Bagged Apple Fruit in China.

Apple fruit spot disease has caused serious economic losses for years in China since the widespread application of fruit bagging in production. Although the three genera Trichothecium, Alternaria, and Acremonium have been reported to be the causal agents, studies on the disease etiology and pathogen biology are still sparse. Here, we report characterization of eight fungal isolates from lesions on 126 symptomatic fruit samples collected in Shaanxi Province, China. Pathogenicity of the isolates was assessed. DNA sequences were obtained at four loci, including D1/D2 domains of the large-subunit nrRNA gene, internal transcribed spacer regions 1 and 2, 5.8S nrDAN gene, a fragment of the actin gene, and a fragment of the β-tubulin. Based on phylogenetic analysis and morphological features, three new species were found: Acremonium mali, Sarocladium liquanensis, and Sarocladium mali. In addition, we made the first report of Sarocladium terricola as a plant pathogen. Temperature and moisture significantly affected in vitro conidial germination of five Acremonium-like species, and their impact on infection of apple fruit was tested using Acremonium sclerotigenum. Conidia of five species germinated from 15 to 35°C in free water; four of the species had optimum temperature around 25°C, whereas conidia of S. terricola had an optimum temperature of 30°C. Conidial germination rate increased as relative humidity (RH) increased. The five isolates had relatively high conidial germination rates at RH > 97%, with a significant decline at 95% RH. Incidence of infection also increased in proportion to RH. In free water, conidial germination was relatively unaffected by temperature.

Evaluation of Fungicide for the Management of Leaf and Fruit Spot (Phaeoramularia angolensis) of Sweet Orange in West &amp; Kellem Wollaga Zones

Sweet orange (Citrus sinensis) is an important fruit crop in the daily diet, good source of food nutrients, cash to the farmers. The leaf and fruit spot disease caused by Phaeoramularia angolensis is one of the most devastating airborne diseases and also the main constraints contributing to the low productivity of citrus plantation in 20 African countries including Ethiopia. The experiment was conducted to evaluate three fungicide (Unizeb 80% WP, Trust-cymocop 439.5 WP, and Benomyl 500 WP) and combination of the two each fungicide under field conditions for the management of leaf and fruit spot disease and also to assess the yield losses. Not significant different in disease incidence between treatments and there was a significant difference in the leaf and fruit spot disease severity and Area under Disease Progressive Curve (AUDPC) among treatments. On the final date of disease assessment, among the fungicide, Unizeb sprayed was recorded the lowest disease severity (17.33%) and (18.17%), whereas the highest disease severity of (46.67%) and (45.83 %) were recorded on leaf and fruit spot on control plots, respectively. The highest fruit yield of 6.14 and 5.94 t/ha were also recorded from plots sprayed with Unizeb 80% WP and Benomyl 500 WP fungicide. Unizeb 80% WP fungicide applied exhibited maximum partial cost net benefit from all plots that means the highest (123970.00 ETB ha -1 ) was recorded and followed by Benomyl 500 WP (111520.00 ETB ha -1 ) fungicide treated plots. The results of the present study revealed that the novel possibility of using Unizeb foliar spray with four times which was found to be an effective in decreasing leaf and fruit spot disease symptoms on sweet orange in Kellem Wollega, Western Oromiya and increased yield. Keywords: Sweet Orange, Leaf and Fruit spot disease, Fungicides, Yield and Cost benefit. DOI : 10.7176/JBAH/9-5-01 Publication date :March 31 st 2019

Spatial Organisation Influences Citrus &amp;lt;i&amp;gt;Pseudocercospora&amp;lt;/i&amp;gt; Leaf and Fruit Spot Disease Severity in Cocoa-Based Agroforestry Systems

An investigation to assess the spatial structure and severity of Pseudocercospora leaf and fruit spot disease (PLFSD) on citrus trees in cocoa-based agroforests was carried out in three contrasting ecological zones in southern Cameroon, viz: 1) the humid forest zone, 2) the degraded forest zone, and 3) the forest-savannah transition zone. Two main parameters were investigated viz: 1) the spatial structure of cocoa based agroforests, and 2) the disease severity. In total, the spatial structure of 19 cocoa-based agroforests was analysed using the Ripley K(r) function, meanwhile the collection of epidemiological data that consisted of noting the presence of PLFSD spots on leaves and fruits on 438 citrus trees was used to characterise the severity of the disease. Results showed that, the spatial structure of citrus trees in these agroforests investigated were regular in seven plots, random in nine, and aggregated in three. Aggregated plots presented a significantly higher mean of disease severity on leaves and fruits (28.55 and 30.37 respectively), as compared to randomised (20.91 and 16.32 respectively) and regular plots (16.28 and 14.97 respectively), at P-value

Management of Exobasidium leaf and fruit spot disease of blueberry

Management of Exobasidium leaf and fruit spot disease of blueberry

Screening of Pear Germplasm against Entomosporium Leaf and Fruit Spot Disease

Screening of Pear Germplasm against Entomosporium Leaf and Fruit Spot Disease

Frequent Association of Colletotrichum Species with Citrus Fruit and Leaf Spot Disease Symptoms and their Genetic Diversity in Ethiopia.

Citrus leaf and fruit spot is one of the most important biotic constraints of citrus production in Ethiopia. The symptomatic leaf and fruit samples were collected from 29 orchards of 15 major citrus growing districts of Ethiopia. One hundred sixty-seven fungal isolates were recovered and identified to species level through DNA barcoding; and their relationships were established using multigene phylogeny. The internal transcribed spacers, long subunit and actin gene sequences revealed that those 167 isolates belonged to either Collectotrichum gloeosporioides or Collectotrichum boninense species complexes (sensu lato), but no recovery of Pseudocercospora angolensis, the primary causal agent of the citrus leaf and fruit spot disease. Detached leaf assays confirmed pathogenicity of isolates of both C. gloeosporioides and C. boninense species complexes on citrus. They reproduced disease symptoms and the pathogens were re-isolated from symptomatic tissues. This study reports frequent association of C. gloeosporioides and C. boninense species complexes with citrus fruit and leaf spot disease in Ethiopia. This finding suggests the need for in-depth studies to determine the roles of C. gloeosporioides and C. boninense species complexes in citrus fruit and leaf spot disease epidemiology.

Development of Microsatellite Markers and Analysis of Genetic Diversity and Population Structure of Colletotrichum gloeosporioides from Ethiopia.

Twenty three polymorphic microsatellite markers were developed for citrus plant pathogenic fungus, Colletotrichum gloeosporioides, and were used to analyze genetic diversity and population structure of 163 isolates from four different geographical regions of Ethiopia. These loci produced a total of 118 alleles with an average of 5.13 alleles per microsatellite marker. The polymorphic information content values ranged from 0.104 to 0.597 with an average of 0.371. The average observed heterozygosity across all loci varied from 0.046 to 0.058. The gene diversity among the loci ranged from 0.106 to 0.664. Unweighted Neighbor-joining and population structure analysis grouped these 163 isolates into three major groups. The clusters were not according to the geographic origin of the isolates. Analysis of molecular variance showed 85% of the total variation within populations and only 5% among populations. There was low genetic differentiation in the total populations (FST = 0.049) as evidenced by high level of gene flow estimate (Nm = 4.8 per generation) among populations. The results show that Ethiopian C. gloeosporioides populations are generally characterized by a low level of genetic diversity. The newly developed microsatellite markers were useful in analyzing the genetic diversity and population structure of the C. gloeosporioides populations. Information obtained from this study could be useful as a base to design strategies for better management of leaf and fruit spot disease of citrus in Ethiopia.

Citrus Production, Constraints and Management Practices in Ethiopia: The Case of &lt;i&gt;Pseudocercospora&lt;i&gt; Leaf and Fruit Spot Disease

Citrus is economically important fruit crop in Ethiopia. However, its production is seriously constrained by various diseases including Pseudocercospora leaf and fruit spot. Surveys were conducted between June 2012 and May 2013 in the main citrus production areas of the country to assess the spread of the disease, and to determine its incidence and severity. A total of forty-nine citrus orchards in twenty-eight districts were surveyed. Random sampling techniques were used for data collection. The results showed that the disease had prevailed and widely spread in the districts assessed in the wet humid areas of the south, southwest, northwest, and north central parts, but not in the low altitude drier areas of the central rift valley and the eastern region of the country. Accordingly, 63.3% of the orchards surveyed were infected with the disease. The overall mean incidences of the disease on leaves of sweet orange, mandarin, lemon and lime were 36.2, 21.5, 17.1 and 16.3% while disease severity ratings were 2.6, 2.3, 2.0 and 1.7, respectively. Similarly, the average incidences and severities on fruits were 63.8, 29.4, 18.0 and 16.7%, and 4.0, 3.0, 2.0 and 2.0, in the same order. However, disease incidences in the different orchards ranged from zero to 76.7% on leaves and from zero to 100% on fruits. Disease severity ratings also varied from one to five on both leaves and fruits. In general, citrus orchards in the south and southwest Ethiopia that are known to have high rainfall and humidity conditions were more severely affected by the disease than those in the northwest and north central parts of the country. In these areas, respondents indicated that many farmers completely abandoned their citrus trees due to this disease. The causative agent was also identified to be the fungus Pseudocercospora angolensis based on cultural and morphological characteristics, and pathogenicity tests of representative isolates obtained from infected leaf and fruit samples.Keywords: Citrus Leaf and fruit spot disease; Pseudocercospora angolensis; Ethiopia

Acremonium Brown Spot, a New Disease Caused by Acremonium sclerotigenum on Bagged Apple Fruit in China.

In China, covering developing apple (Malus × domestica) fruit with paper bags is a standard production practice. The fruit are usually covered from May to October to exclude pests and rain-dispersed pathogens and reduce pesticide residue at harvest. From 2010 to 2012, a fruit spot disease was observed on bagged fruit and caused 1 to 30% annual yield losses in most orchards in Shandong Province. Affected fruit were covered with red-brown, sunken, circular lesions 2 to 20 mm in diameter with dark violet edges often surrounded by a red halo. In many cases, the lesion cracked and pinkish mycelium was observed within the cracks. Isolations were made from bagged fruit from 12 orchards in October 2010 to 2012. Fungal isolations were made onto potato dextrose agar (PDA) medium. Two strains were consistently obtained from isolates. Strain 1 produced conidia assembled in head. Conidia were ellipsoidal to ovoid and 2.1 to 7.5 × 1.1 to 3.0 μm. Colonies were whitish with some pink and powdery on PDA. String 2 produced conidia in a long chain. Conidia were spindle-shaped with apiculate at both ends and 2.1 to 6.6 × 1.3 to 3.8 μm. Colonies were whitish at the beginning and grayish later and powdery on PDA. To further confirm the identity of the isolated fungus, the large subunit (LSU), the small subunit (SSU), and the internal transcribed spacer (ITS) sequences of ribosomal DNA, and the β-tubulin gene (β-tubulin), were amplified and sequenced with the primers V9G/LR5, NS1/NS24, ITS1/ITS4, and Bt1a/Bt1b, respectively. LSU (GenBank Accession Nos. KJ194115 and KJ194116), SSU (KJ194117 and KJ194118), ITS (KF225143 and KF225144), and β-tubulin (KF225145 and KF225146) sequences didn't have any variation between the two strains sequenced. Phylogenetic analyses of each of the examined genes indicated a high similarity (>99%) with Acremonium sclerotigenum (CBS 384.65 HQ232129). Based on the sequence data and the morphology, we identified the fungus as A. sclerotigenum (1,2). To confirm pathogenicity, a spore suspension (1 × 104 conidia per ml) was made from each of the strains isolated. Strains were subsequently inoculated on to 10 mature apple fruit by wounding them to a depth of 2 mm with an acupuncture needle. Inoculation with sterile distilled water was included as a control. Prior to inoculation, all fruit were surface-sterilized with 75% alcohol. Lesions developed on fruit inoculated with the putative pathogen 10 days after incubation in >90% humidity chamber at 25°C. The fungi that were isolated from the infected fruit were identical to the inoculated strains. No lesions developed on the control fruit. This is the first report of brown spot disease caused by A. sclerotigenum in apple and in bagged fruit production. Given that brown spot disease symptoms were usually observed in September after long periods of rain, management efforts need to focus on protecting bagged fruit before harvest.