Tree age and cultivar‐oriented use of mineral oil added to fungicide tank mixture for the control of citrus black spot in sweet orange orchards

2021 ◽  
Author(s):  
Geraldo José Silva Júnior ◽  
Mario Roberto Moraes ◽  
Rafaele Regina Moreira ◽  
Franklin Behlau
Keyword(s):  
Sweet Orange ◽  
Black Spot ◽  
Mineral Oil ◽  
Tree Age ◽  
Citrus Black Spot

Citrus black spot severity related to premature fruit drop in sweet orange orchards

2021 ◽  
Author(s):  
Franklin Jackson Machado ◽  
Fabrício Eustáquio Lanza ◽  
Marcela Olivetti Ferretti ◽  
Régis Oliveira Fialho ◽  
Franklin Behlau ◽  
...  
Keyword(s):  
Sweet Orange ◽  
Black Spot ◽  
Citrus Black Spot ◽  
Fruit Drop

scholarly journals First Report of Guignardia citricarpa Associated with Citrus Black Spot on Sweet Orange (Citrus sinensis) in North America

Plant Disease ◽  
2012 ◽  
Vol 96 (8) ◽  
pp. 1225-1225 ◽  
Author(s):  
T. S. Schubert ◽  
M. M. Dewdney ◽  
N. A. Peres ◽  
M. E. Palm ◽  
A. Jeyaprakash ◽  
...  
Keyword(s):  
North America ◽  
Sweet Orange ◽  
Black Spot ◽  
The United States ◽  
Yield Reduction ◽  
Rrna Gene ◽  
Specific Primers ◽  
Oatmeal Agar ◽  
First Report ◽  
Citrus Black Spot

In March 2010, citrus black spot symptoms were observed on sweet orange trees in a grove near Immokalee, FL. Symptoms observed on fruit included hard spot, cracked spot, and early virulent spot. Hard spot lesions were up to 5 mm, depressed with a chocolate margin and a necrotic, tan center, often with black pycnidia (140 to 200 μm) present. Cracked spot lesions were large (15 mm), dark brown, with diffuse margins and raised cracks. In some cases, hard spots formed in the center of lesions. Early virulent spot lesions were small (up to 7 mm long), bright red, irregular, indented, and often with many pycnidia. In addition, small (2 to 3 mm), elliptical, reddish brown leaf lesions with depressed tan centers were observed on some trees with symptomatic fruit. Chlorotic halos appeared as they aged. Most leaves had single lesions, occasionally up to four per leaf. Tissue pieces from hard spots and early virulent spots were placed aseptically on potato dextrose agar (PDA), oatmeal agar, or carrot agar and incubated with 12 h of light and dark at 24°C. Cultures that grew colonies within a week were discarded. Fourteen single-spore cultures were obtained from the isolates that grew slower than the Guignardia mangiferae reference cultures, although pycnidia formed more rapidly in the G. mangiferae cultures (1). No sexual structures were observed. Cultures on half-PDA were black and cordlike with irregular margins with numerous pycnidia, often bearing white cirrhi after 14 days. Conidia (7.1 to 7.8 × 10.3 to 11.8 μm) were hyaline, aseptate, multiguttulate, ovoid with a flattened base surrounded by a hyaline matrix (0.4 to 0.6 μm) and a hyaline appendage on the rounded apex, corresponding to published descriptions of G. citricarpa (anomorph Phyllosticta citricarpa) (1). A yellow pigment was seen in oatmeal agar surrounding G. citricarpa, but not G. mangiferae colonies as previously reported (1,2). DNA was extracted from lesions and cultures and amplified with species-specific primers (2). DNA was also extracted from G. mangiferae and healthy citrus fruit. The G. citricarpa-specific primers produced a 300-bp band from fruit lesions and pure cultures. G. mangiferae-specific primers produced 290-bp bands with DNA from G. mangiferae cultures. The internally transcribed spacer (ITS) of the rRNA gene, translation-elongation factor (TEF), and actin gene regions were sequenced from G. citricarpa isolates and deposited in GenBank. These sequences had 100% homology with G. citricarpa ITS sequences from South Africa and Brazil, 100% homology with TEF, and 99% homology with actin of a Brazilian isolate. Pathogenicity tests with G. citricarpa were not done because the organism infects immature fruit and has an incubation period of at least 6 months (3). In addition, quarantine restrictions limit work with the organism outside a contained facility. To our knowledge, this is the first report of black spot in North America. The initial infested area was ~57 km2. The disease is of great importance to the Florida citrus industry because it causes serious blemishes and significant yield reduction, especially on the most commonly grown ‘Valencia’ sweet orange. Also, the presence of the disease in Florida may affect market access because G. citricarpa is considered a quarantine pathogen by the United States and internationally. References: (1) R. P. Baayen et al. Phytopathology 92:464, 2002. (2) N. A. Peres et al. Plant Dis. 91:525, 2007 (3) R. F. Reis et al. Fitopath Bras. 31:29, 2006.

scholarly journals Application of Azoxystrobin for Control of Benomyl-Resistant Guignardia citricarpa on ‘Valencia’ Oranges in South Africa

Plant Disease ◽  
2003 ◽  
Vol 87 (7) ◽  
pp. 784-788 ◽  
Author(s):  
G. C. Schutte ◽  
R. I. Mansfield ◽  
H. Smith ◽  
K. V. Beeton
Keyword(s):  
South Africa ◽  
Disease Control ◽  
Untreated Control ◽  
Black Spot ◽  
Mineral Oil ◽  
Guignardia Citricarpa ◽  
Citrus Black Spot ◽  
Oil In Water ◽  
Small Plot

Azoxystrobin was evaluated in replicated small-plot trials from 1995 to 1999 for control of citrus black spot (CBS) on ‘Valencia’ oranges caused by Guignardia citricarpa. Applications of different rates of tank mixes of azoxystrobin and mancozeb during the susceptible period from October to January were compared with an untreated control as well as the standard four applications of mancozeb with or without mineral oil (1.20 g a.i./liter + 0.5% [vol/vol]/liter and 1.60 g a.i./liter of water, respectively). Two applications of azoxystrobin in tank mixtures with mancozeb and mineral oil (0.5% [vol/vol]/liter) in mid-November and mid-January at rates of 0.10, 0.15, and 0.20 g a.i./liter controlled CBS by more than 98 to 99%, 99 to 100% and 95 to 98%, respectively. Concomitantly, where mineral oil was not added to the fungicide mixture, azoxystrobin and mancozeb resulted only in 73 to 95%, 74 to 93% and 92.2 to 92.3% CBS control, respectively. Tank mixtures of benomyl, mancozeb, and mineral oil reduced CBS by only 29%, which could be attributed to the presence of benomyl-resistant pathogen isolates in the experimental orchard. Azoxystrobin applied at rates of 0.05, 0.075, and 0.10 g a.i./liter in tank mixtures with mancozeb (1.2 g a.i./liter) and mineral oil (0.5% [vol/vol]/liter of water) or Agral 90 (0.5% [vol/vol]/liter of water) were equally effective, reducing CBS by more than 99%. When mineral oil was compared to different adjuvants in tank mixtures with azoxystrobin and mancozeb, only mineral oil resulted in 100% clean exportable fruit. There was no difference between Sunspray 6E and Bac oil when mixed with azoxystrobin and mancozeb on the degree of disease control. Furthermore, the concentration of mineral oil in water can be lowered from 0.5% (vol/vol)/liter of water to 0.3% (vol/vol)/liter of water without a loss in efficacy against CBS. It is therefore, recommended that azoxystrobin (0.075 g a.i./liter) must be applied in tank mixtures with mancozeb (1.2 g a.i./liter) and mineral oil, which can be applied at either 0.5% (vol/vol)/liter of water or 0.3% (vol/vol)/liter of water.

scholarly journals Exotic Diseases of Citrus Identification Sheet

EDIS ◽  
2009 ◽  
Vol 2009 (4) ◽  
Author(s):  
Megan M. Dewdney ◽  
Jamie D. Burrow (Yates) ◽  
Michael E. Rogers ◽  
Timothy M. Spann
Keyword(s):  
Plant Pathology ◽  
Sweet Orange ◽  
Black Spot ◽  
Citrus Variegated Chlorosis ◽  
Citrus Black Spot ◽  
Stem Pitting ◽  
Citrus Tristeza

PP264, a 2-page ID sheet by M.M. Dewdney, J.D. Burrow (Yates), M.E. Rogers, and T.M. Spann, provides images for identification and a comparison chart for Citrus Variegated Chlorosis (CVC), Leprosis, Citrus Black Spot, Sweet Orange Scab (SOS), and Citrus Tristeza Stem-Pitting (CTV-SP). Published by the UF Department of Plant Pathology, April 2009. PP264/PP264: Exotic Diseases of Citrus (ufl.edu)  

scholarly journals Genetic Diversity and Population Differentiation of the Causal Agent of Citrus Black Spot in Brazil

2012 ◽  
Vol 2012 ◽  
pp. 1-14 ◽  
Author(s):  
Ester Wickert ◽  
Antonio de Goes ◽  
Andressa de Souza ◽  
Eliana Gertrudes de Macedo Lemos
Keyword(s):  
Genetic Diversity ◽  
Genetic Structure ◽  
Population Differentiation ◽  
Sweet Orange ◽  
Black Spot ◽  
Pathogenic Fungi ◽  
Its2 Region ◽  
Citrus Black Spot ◽  
Different Populations ◽  
Different Origins

One of the most important diseases that affect sweet orange orchards in Brazil is the Citrus Black Spot that is caused by the fungusGuignardia citricarpa. This disease causes irreparable losses due to the premature falling of fruit, as well as its severe effects on the epidermis of ripe fruit that renders them unacceptable at the fresh fruit markets. Despite the fact that the fungus and the disease are well studied, little is known about the genetic diversity and the structure of the fungi populations in Brazilian orchards. The objective of this work was study the genetic diversity and population differentiation ofG. citricarpaassociated with four sweet orange varieties in two geographic locations using DNA sequence of ITS1-5.8S-ITS2 region from fungi isolates. We observed that different populations are closely related and present little genetic structure according to varieties and geographic places with the highest genetic diversity distributed among isolates of the same populations. The same haplotypes were sampled in different populations from the same and different orange varieties and from similar and different origins. If new and pathogenic fungi would become resistant to fungicides, the observed genetic structure could rapidly spread this new form from one population to others.

scholarly journals Control of Guignardia citricarpa by Bacillus subtilis and Trichoderma spp.

2011 ◽  
Vol 33 (4) ◽  
pp. 1111-1118 ◽  
Author(s):  
Katia Cristina Kupper ◽  
Élida Barbosa Corrêa ◽  
Cristiane Moretto ◽  
Wagner Bettiol ◽  
Antonio de Goes
Keyword(s):  
Bacillus Subtilis ◽  
Sweet Orange ◽  
Black Spot ◽  
Disease Index ◽  
Control Treatment ◽  
Biological Control Agents ◽  
Trichoderma Spp ◽  
Fungicide Treatment ◽  
The Third ◽  
Citrus Black Spot

The ability of isolates of Bacillus subtilis and Trichoderma spp. to control citrus black spot (CBS) was investigated in ´Natal´ sweet orange orchards. The first experiment was conducted during the 2001/2002 season and four isolates of B. subtilis (ACB-AP3, ACB-69, ACB-72 and ACB-77), applied every 28 days, alone or in combination were tested and compared with fungicide treatments. Two other experiments were carried out during the 2002/2003 season, where the same isolates of Bacillus and two isolates of Trichoderma (ACB-14 and ACB-40) were tested being applied every 28 days in the second experiment, and every 15 days in the third experiment. In the first experiment, the treatment with ACB-69 differed statistically from the control, but did not differ from other biological control agents or mixture of Bacillus isolates. In the second experiment, the treatments with ACB-69 and ACB-AP3 resulted in smaller disease index compared with the control treatment. However, this result was not repeated in the third experiment, where the isolates were applied every 15 days. Disease severity was high in both evaluated seasons and the fungicide treatment was the most effective for disease control.

scholarly journals Sweet Orange Fruit Age and Inoculum Concentration Affect the Expression of Citrus Black Spot Symptoms

Plant Disease ◽  
2019 ◽  
Vol 103 (5) ◽  
pp. 913-921 ◽  
Author(s):  
Guilherme F. Frare ◽  
Geraldo J. Silva-Junior ◽  
Fabrício E. Lanza ◽  
Renato B. Bassanezi ◽  
Thiago G. Ramires ◽  
...  
Keyword(s):  
Incubation Period ◽  
Sweet Orange ◽  
Disease Incidence ◽  
Black Spot ◽  
Conidial Germination ◽  
Inoculum Concentration ◽  
Factors Affecting ◽  
Citrus Black Spot ◽  
Incubation Periods ◽  
Orange Fruit

Citrus black spot (CBS), caused by Phyllosticta citricarpa, affects different citrus species worldwide. CBS is mainly expressed as false melanose and hard spot symptoms. There is no consensus in the literature about the period when fruit are susceptible to P. citricarpa infection and the length of the CBS incubation period. Therefore, this study aimed to assess the influence of sweet orange variety, fruit age, and inoculum concentration on the incubation period and the expression of different CBS symptoms. Attached fruit of Hamlin, Pera, and Valencia sweet orange at 1.5, 3.0, 5.0, and 7.0 cm diameter were inoculated with suspensions containing 103 and 105 conidia/ml of P. citricarpa. The percent conidial germination was quantified using scanning electron microscopy. The CBS symptoms on fruit were assessed monthly. The four diameters did not significantly affect conidial germination on the inoculated fruit, although CBS incidences were lower when larger fruit were inoculated. Hard spot symptoms on sweet orange fruit did not develop from the false melanose symptoms and vice versa. The incubation periods for false melanose were shorter than those observed for hard spot. False melanose began to appear 44 days after inoculation, but hard spot only formed at 113 days or later. Incubation periods were shorter and incidences of false melanose were higher following inoculation with higher inoculum concentration and smaller fruit diameter. The incubation period of hard spot varied among varieties and fruit diameters. However, there was no relationship between hard spot incidence and variety. This study provides a better understanding of the factors affecting the variation in the CBS incubation period and disease incidence on fruit.

scholarly journals Nonpathogenic Isolates of the Citrus Black Spot Fungus, Guignardia citricarpa, Identified as a Cosmopolitan Endophyte of Woody Plants, G. mangiferae (Phyllosticta capitalensis)

2002 ◽  
Vol 92 (5) ◽  
pp. 464-477 ◽  
Author(s):  
R. P. Baayen ◽  
P. J. M. Bonants ◽  
G. Verkley ◽  
G. C. Carroll ◽  
H. A. van der Aa ◽  
...  
Keyword(s):  
United States ◽  
European Union ◽  
Woody Plants ◽  
Black Spot ◽  
The United States ◽  
The European Union ◽  
Citrus Fruits ◽  
Citrus Black Spot ◽  
Group I ◽  
Group Ii

The population structure of Guignardia citricarpa sensu lato (anamorph: Phyllosticta citricarpa), a fungus of which strains pathogenic to citrus are subject to phytosanitary legislation in the European Union and the United States, was investigated. Internal transcribed spacer sequences revealed two phylogenetically distinct groups in G. citricarpa. This distinction was supported by amplified fragment length polymorphism analysis that also supported the exclusion of two isolates that had apparently been misclassified as G. citricarpa. On cherry decoction agar, but not on other media, growth rates of group I isolates were lower than those of group II isolates. Conidial dimensions were similar, but group I isolates formed conidia with barely visible mucoid sheaths, whereas those of group II formed conidia with thick sheaths. Cultures of isolates belonging to group I produced rare infertile perithecia, whereas fertile perithecia were formed by most isolates of group II. Colonies of isolates belonging to group I were less dark than those of group II, with a wider translucent outer zone and a lobate rather than entire margin. On oatmeal agar, exclusively group I isolates formed a yellow pigment. Group I harbored strains from citrus fruits with classical black spot lesions (1 to 10 mm in diameter) usually containing pycnidia. Group II harbored endophytic strains from a wide range of host species, as well as strains from symptomless citrus fruits or fruits with minute spots (<2-mm diameter) without pycnidia. These observations support the historic distinction between slowly growing pathogenic isolates and morphologically similar fast-growing, nonpathogenic isolates of G. citricarpa. The latter proved to belong to G. mangiferae (P. capitalensis), a ubiquitous endophyte of woody plants with numerous probable synonyms including G. endophyllicola, G. psidii, P. anacardiacearum, and P. theacearum. G. mangiferae occurs in the European Union and the United States on many host species including citrus, and does not cause symptoms of citrus black spot, justifying its exclusion from quarantine measures.

scholarly journals The Effects of Nutrition and Environmental Factors on Conidial Germination and Appressorium Formation of Phyllosticta citricarpa, the Causal Agent of Citrus Black Spot

2019 ◽  
Vol 109 (4) ◽  
pp. 650-658 ◽  
Author(s):  
Nan-Yi Wang ◽  
Megan M. Dewdney
Keyword(s):  
Black Spot ◽  
Nitrogen Sources ◽  
Conidial Germination ◽  
Appressorium Formation ◽  
Potato Dextrose Broth ◽  
Citrus Black Spot ◽  
Fungal Biology ◽  
Biological Studies ◽  
Phyllosticta Citricarpa

Citrus black spot, caused by Phyllosticta citricarpa, has been identified in Florida since 2010 and can reduce fruit yield and marketability. The conditions required for conidial germination have been poorly understood for P. citricarpa, limiting further biological studies. In this study, the effects of citrus juices, concentration, pH, various carbon and nitrogen sources, and environmental conditions were evaluated in vitro. All tested juices, especially ‘Valencia’ (>85%, P < 0.05), favored germination and appressorium formation, whereas sterile water rarely stimulated germination (<1%). The ‘Valencia’ juice effect was concentration and pH dependent, and the maximum rate was reached in 1.5% juice with pH of 3.4. Most carbon, nitrogen, or complex sources did not favor germination or appressorium formation, with the exception of potato dextrose broth. An incubation period of 18 to 24 h at 24°C was required for peak germination and appressorium formation. The further analysis of critical juice components using synthetic citrus juice revealed that sugars, salts, citric acid, and thiamine were most important for germination and appressorium formation (>80%, P > 0.05). These results provide a better understanding of fungal biology of P. citricarpa and a robust and convenient system for further applications such as screening for efficacious fungicides.

scholarly journals A One-Day Sensitive Method to Detect and Distinguish Between the Citrus Black Spot Pathogen Guignardia citricarpa and the Endophyte Guignardia mangiferae

Plant Disease ◽  
2006 ◽  
Vol 90 (1) ◽  
pp. 97-101 ◽  
Author(s):  
L. Meyer ◽  
G. M. Sanders ◽  
R. Jacobs ◽  
L. Korsten
Keyword(s):  
South African ◽  
Sequence Data ◽  
Black Spot ◽  
The United States ◽  
Guignardia Citricarpa ◽  
Competitive Edge ◽  
Citrus Black Spot ◽  
Species Specific ◽  
Time Required ◽  
Slow Growing

If South African citrus exporters wish to retain their competitive edge in the European market and access new markets such as the United States of America, it is of quarantine importance to distinguish between the citrus black spot pathogen, Guignardia citricarpa, and the harmless endophyte, G. mangiferae. The endophyte is not a sanitary or phytosanitary concern. This paper describes the design of species-specific primers that are able to detect and distinguish between these two Guignardia species. Application of the primer set CITRIC1 and CAMEL2 in conjunction with the ITS4 primer yielded polymerase chain reaction (PCR) amplicons of approximately 580 bp and 430 bp for G. citricarpa and G. mangiferae, respectively. Results obtained with these primers are in accordance with sequence data, and repeated tests verified accuracy and sensitivity. A BLAST search revealed no matches other than G. citricarpa and G. mangiferae, and no positive PCR results were obtained with Colletotrichum gloeosporioides, which is the most common contaminant in black spot lesions. We are, therefore, able to distinguish G. citricarpa and G. mangiferae unequivocally using a PCR-based method. This method was further improved to directly isolate DNA from fruit lesions by means of the DNeasy Plant Mini Kit (Qiagen). This eliminates the prior need for culturing the slow-growing organism, thereby shortening the time required to one day to test for and verify the presence or absence of the pathogenic G. citricarpa in export consignments.

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