Variability in Pathogenicity among Tunisian Isolates of Phytophthora cactorum as Measured by Their Ability to Cause Crown Rot on Four Apple Cultivars and MM106 Roostock

2006 ◽  
Vol 5 (2) ◽  
pp. 321-325
Author(s):  
N. Boughalleb . ◽  
A. Moulahi . ◽  
M. El Mahjoub .
Keyword(s):  
Crown Rot ◽  
Phytophthora Cactorum ◽  
Apple Cultivars

scholarly journals First report of crown rot of Photinia fraseri caused by Phytophthora cactorum

2006 ◽  
Vol 55 (4) ◽  
pp. 573-573 ◽  
Author(s):  
A. M. Vettraino ◽  
L. Antonacci ◽  
L. Flamini ◽  
P. Nipoti ◽  
E. Rossini ◽  
...  
Keyword(s):  
Crown Rot ◽  
Phytophthora Cactorum ◽  
First Report

STUDIES OF CROWN ROT OF APPLE TREES

1942 ◽  
Vol 20c (9) ◽  
pp. 457-490 ◽  
Author(s):  
Maurice F. Welsh
Keyword(s):  
Soil Moisture ◽  
Apple Tree ◽  
Disease Incidence ◽  
Antagonistic Effect ◽  
Crown Rot ◽  
Phytophthora Cactorum ◽  
Additional Information ◽  
Two Factors ◽  
Below Ground ◽  
Old Trees

The form of apple tree crown rot that occurs in the irrigated orchards of British Columbia is confined to the below-ground bark tissues of the tree. It has been encountered in trees of all ages and of all the commercial varieties.Proof is given that this crown rot is caused by the fungus Phytophthora cactorum (L. & C.) Schroet. Typical symptoms of the disease have been reproduced in over 200 trees of various ages as a result of their inoculation with this fungus. Isolation has been possible only from the margins of active lesions, and has proved difficult even from these tissues. There is evidence that the activity of P. cactorum is inhibited in rotted tissues by the antagonistic effect of one or more secondary organisms.The influence of soil moisture and temperature on disease incidence has been studied by field observations and by the inoculation of two-year—old trees under controlled conditions in Wisconsin tank equipment in the greenhouse. The effects of these two factors seem to be interrelated, with the highest incidence of disease in an almost saturated soil at the highest temperature imposed, 32 °C. The influence of soil moisture is exerted particularly in the subsoil, rather than in the locus of crown rot attack.Certain varieties of apple have been found to vary in their resistance to crown rot. Deep wounds have proved necessary to allow entry of the fungus into bark tissues.The additional information now available is being utilized in a search for improved means of combating the disease.

scholarly journals Meristem culture for the elimination of the strawberry crown rot pathogen Phytophthora cactorum

2011 ◽  
Vol 1 (3) ◽  
pp. 129-136 ◽  
Author(s):  
A.B. Whitehouse ◽  
C.L. Govan ◽  
K.J. Hammond ◽  
D.J. Sargent ◽  
D.W. Simpson
Keyword(s):  
Crown Rot ◽  
Meristem Culture ◽  
Phytophthora Cactorum

scholarly journals First Notice of Phytophthora Aerial Blight and Crown Rot on Pansies in Poland

2010 ◽  
Vol 50 (2) ◽  
pp. 233-237 ◽  
Author(s):  
Leszek Orlikowski ◽  
Magdalena Pļaszek ◽  
Adam Wojdyļa ◽  
Czesļaw Skrzypczak
Keyword(s):  
Botrytis Cinerea ◽  
Malus Domestica ◽  
Pythium Ultimum ◽  
Crown Rot ◽  
Fusarium Avenaceum ◽  
Phytophthora Cactorum ◽  
Disease Symptoms ◽  
Necrotic Spots ◽  
Begonia Semperflorens

First Notice ofPhytophthoraAerial Blight and Crown Rot on Pansies in PolandPhytophthora cactorumwas detected on &9/10; of pansies showing yellowing of leaves and crown rot symptoms and constituted about 90% of isolates obtained.Botrytis cinerea, Fusarium avenaceum, F. solaniandPythium ultimumwere also isolated from diseased tissues. Using rhododendron leaves as the bait,P. cactorumwas detected in pansy substratum as well as from soil under the mata. Isolates obtained from diseased plants, substratum and soil under mata colonized leaves, stem parts and roots of pansy. Necroses spread faster on organs inoculated with cultures from plants and substratum. Among 25 cultivars inoculated withP. cactorum, disease symptoms did not occur on 3 of them, whereas the fastest spread of necrotic spots (3.8 mm/24 hrs) was noticed on 3 cultivars. Isolates ofP. cactorumfromBegonia semperflorensandMalus domesticacolonized leaf petioles of pansy with significantly faster spread when isolates from begonia and pansy were used for inoculation.

scholarly journals First Report of Resistance to Mefenoxam in Phytophthora cactorum in the United States and Elsewhere

Plant Disease ◽  
2004 ◽  
Vol 88 (5) ◽  
pp. 576-576 ◽  
Author(s):  
S. N. Jeffers ◽  
G. Schnabel ◽  
J. P. Smith
Keyword(s):  
United States ◽  
South Carolina ◽  
Tap Water ◽  
Southeastern United States ◽  
Crop Protection ◽  
The United States ◽  
Crown Rot ◽  
Phytophthora Cactorum ◽  
Mycelium Growth ◽  
First Report

Phytophthora cactorum causes crown rot of strawberry (Fragaria × ananassa) (2), a disease that has been particularly severe during the last 5 years in the southeastern United States. In the fall of 2001, strawberry plants (cv. Camarosa) in a field in Lexington County, South Carolina exhibited typical crown rot symptoms (2) 1 to 2 weeks after transplanting, even though plants had been drenched with mefenoxam (Ridomil Gold; Syngenta Crop Protection, Greensboro, NC) immediately after transplanting. Initially, we observed leaves that had marginal necrosis, were smaller than normal, and were discolored. Soon after, diseased plants appeared stunted and unthrifty compared with other plants in the field, and some of these plants eventually wilted and died. Severely affected plants had necrotic roots and decayed crowns. Ten symptomatic plants were collected for isolation. In the laboratory, root and crown tissues were rinsed in running tap water and blotted dry, small pieces of necrotic tissue were placed aseptically on PAR-V8 selective medium (1), and isolation plates were placed at 20°C in the dark for up to 7 days. P. cactorum was recovered from six plants. Isolates produced characteristic asexual and sexual structures directly on the isolation plates (i.e., papillate sporangia on sympodial sporangiophores and oospores with paragynous antheridia) (2). A single hypha of an isolate from each plant was transferred to fresh PAR-V8, and pure cultures were stored on cornmeal agar in glass vials at 15°C in the dark. All six isolates from the Lexington County field and nine other isolates of P. cactorum from strawberry (three from South Carolina, three from North Carolina, and three from Florida) were tested for sensitivity to mefenoxam on fungicide-amended medium. Mefenoxam was added to 10% clarified V8 juice agar (cV8A) after autoclaving so the concentration in the medium was 100 ppm. Agar plugs from active colonies were transferred to mefenoxam-amended and nonamended cV8A (three replicates per treatment), plates were placed at 25°C in the dark for 3 days, and linear mycelium growth was measured. All six isolates from Lexington County were highly resistant to mefenoxam with mycelium growth relatively unrestricted on mefenoxam-amended medium (73 to 89% of that on nonamended medium). In comparison, the other nine isolates were sensitive to mefenoxam with mycelium growth severely restricted by 100 ppm of mefenoxam (0 to 7% of that on nonamended medium). To our knowledge, this is the first report of mefenoxam resistance in P. cactorum on strawberry or any other crop in the United States and elsewhere. Because mefenoxam is the primary fungicide used to manage Phytophthora crown rot in the southeastern United States, resistance may limit use of this fungicide in strawberry production. References: (1) A. J. Ferguson and S. N. Jeffers. Plant Dis. 83:1129, 1999. (2) E. Seemüller. Crown rot. Pages 50–51 in: Compendium of Strawberry Diseases, 2nd ed. J. L. Maas, ed. The American Phytopathological Society, St. Paul, MN, 1998.

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