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 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.

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

scholarly journals Speciesspecific PCR primers for Guignardia citricarpa and Guignardia mangiferae

2006 ◽  
Vol 59 ◽  
pp. 141-145 ◽  
Author(s):  
K.R. Everett ◽  
J. Rees-George
Keyword(s):  
New Zealand ◽  
Venturia Inaequalis ◽  
Black Spot ◽  
Pathogenic Fungi ◽  
Pcr Primers ◽  
Colletotrichum Acutatum ◽  
Botryosphaeria Dothidea ◽  
Guignardia Citricarpa ◽  
Citrus Black Spot ◽  
Polymerase Chain

The plant pathogen Guignardia citricarpa causes citrus black spot and is not considered to be present in New Zealand Speciesspecific polymerase chain reaction (PCR) primers were designed to identify G citricarpa and G mangiferae a closely related saprotroph that is present in New Zealand These PCR primers were tested against a range of other saprotrophic and pathogenic fungi viz Botrytis cinerea Botryosphaeria dothidea B parva Cladosporium sp Colletotrichum acutatum C gloeosporioides Cryptosporiopsis sp Epicoccum sp Nigrospora sp Penicillium sp Pestalotia sp Phialophora sp Phlyctema sp Phoma sp Phomopsis sp Stemphylium sp and Venturia inaequalis The primers JRGGc were specific to G citricarpa and JRGGm to G mangiferae A 226 bp product was amplified from G mangiferae DNA using JRGGm primers and a 501 bp product was amplified from G citricarpa DNA using JRGGc primers These primers thus distinguished G citricarpa from G mangiferae and can be used to rapidly identify incursions by citrus black spot

scholarly journals Rind Stippling on Valencia Oranges by Copper Fungicides Used for Control of Citrus Black Spot in South Africa

Plant Disease ◽  
1997 ◽  
Vol 81 (8) ◽  
pp. 851-854 ◽  
Author(s):  
G. C. Schutte ◽  
K. V. Beeton ◽  
J. M. Kotzé
Keyword(s):  
South Africa ◽  
Black Spot ◽  
The Other ◽  
Copper Oxychloride ◽  
Copper Fungicides ◽  
Citrus Black Spot ◽  
Other Hand ◽  
Wettable Powder ◽  
Cupric Hydroxide ◽  
Protection Period

Four copper sprays and copper mixtures with dithiocarbamates aggravated stippling of the fruit rind of Valencia oranges if sprayed in succession at registered rates during the recommended protection period from October to January for control of citrus black spot in South Africa. Copper stippling was more severe on treatments in which copper oxychloride was sprayed in succession, individually, or in combination with mancozeb or maneb/ZnO. On the other hand, less copper stippling was observed on treatments in which three mancozeb applications were altered with a single copper oxychloride as tank mixtures with or without mancozeb, which was sprayed during midsummer (December and January). Cupric hydroxide resulted in more general copper stippling lesions than any other copper oxychloride spray program. Four successive applications of the wettable powder copper oxychloride formulation resulted in more copper stippling when compared with the suspension concentrate formulation. Stippling was calculated to be more severe with late applications of copper fungicides during December and January. In another experiment, all contact fungicides tested were effective in controlling citrus black spot.

scholarly journals High molecular diversity of the fungus Guignardia citricarpa and Guignardia mangiferae and new primers for the diagnosis of the citrus black spot

2009 ◽  
Vol 52 (5) ◽  
pp. 1063-1073 ◽  
Author(s):  
Danyelle Stringari ◽  
Chirlei Glienke ◽  
Daniel de Christo ◽  
Walter Maccheroni Jr. ◽  
João Lucio de Azevedo
Keyword(s):  
Rapd Markers ◽  
Geographical Origin ◽  
Black Spot ◽  
Polymerase Chain Reaction Analysis ◽  
Causal Agent ◽  
Specific Primers ◽  
Guignardia Citricarpa ◽  
Citrus Black Spot ◽  
Polymerase Chain ◽  
Sequence Characterized Amplified Regions

RAPD markers were used to investigate the distribution of genetic variability among a group of Guignardia citricarpa, G. mangiferae, and Phyllosticta spinarum isolates obtained from several hosts in Brazil, Argentina, Mexico, Costa Rica, Thailand, Japan, United States and South Africa. Pathogenic isolates G. citricarpa Kiely (anamorph form P. citricarpa McAlp Van Der Aa) are the etiological agent of the Citrus Black Spot (CBS), a disease that affects several citric plants and causes substantial injuries to the appearance of their fruits, thus preventing their export. Several previous studies have demonstrated the existence of an endophytic species with high morphological similarity to the causal agent of CBS that could remain latent in the same hosts. Consequently, the identification of the plants and fruits free from the causal agent of the disease is severely hampered. The RAPD analysis showed a clear discrimination among the pathogenic isolates of G. citricarpa and endophytic isolates (G. mangiferae and P. spinarum). In addition, a Principal Coordinate Analysis (PCO) based on a matrix of genetic similarity estimated by the RAPD markers showed four clusters, irrespective of their host or geographical origin. An Analysis of Molecular Variance (AMOVA) indicated that 62.8% of the genetic variation was found between the populations (G. citricarpa, G. mangiferae, P. spinarum and Phyllosticta sp.). Substantial variation was found in the populations (37.2%). Exclusive RAPD markers of isolates of G. citricarpa were cloned, sequenced and used to obtain SCARS (Sequence Characterized Amplified Regions), which allowed the development of new specific primers for the identification of G. citricarpa PCR (Polymerase Chain Reaction) analysis using a pair of primers specific to pathogenic isolates corroborating the groupings obtained by the RAPD markers, underscoring its efficiency in the identification of the causal agent of CBS.

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