First Report of Phytophthora cinnamomi Causing Trunk Canker of Almond in California

Phytophthora cinnamomi was isolated from varieties of Hedera helix pot plants in 1989 in two Danish greenhouse nurseries. The symptoms were brown, rotten roots and stems, and brown areas developing from the base of the leaves. The fungus was isolated directly from roots, stems, leaves, and soil, and by baiting the nutrient solutions of the watering systems with needles of Cedrus deodara. The fungus was isolated on Phytophthora selective agar medium containing hymexazol and identified with the keys of Kröber (1) and Stamps et al. (2). The fungus was characterized by coralloid hyphal swellings, chlamydospores, lack of oogonia in single culture, and production of numerous, ovoid sporangia with a nonpapillate, wide pore. The sporangia produced many zoospores after 2 days flooding with autoclaved pond water on V8 juice agar, followed by internal proliferation. The fungus was also isolated in Norway in 1993 from ivy pot plants. The fungus was widespread in Danish and Norwegian pot plant nurseries in 1997 and caused losses in most varieties, especially at temperatures above 23°C. Effective fungicides are not available for use in Denmark and the disease is easily spread with cuttings, and through the watering system with recirculation of the nutrient solution. A Danish isolate of P. cinnamomi originating from roots of H. helix was used in a pathogenicity test. Five-week-old cuttings were inoculated by adding zoospores (5 per ml) to the recirculating nutrient solution. Control plants were on a separate bench with nutrient solution without the fungus. After 1 week, symptoms of root rot were observed, and 2 weeks after inoculation, 75% of plants expressed severe symptoms on roots, stems, and leaves. P. cinnamomi was reisolated from roots, stems, and leaves of diseased plants, but was not isolated from the control plants. The reisolate was morphologically identical to the original isolate. This is the first report of P. cinnamomi from ivy in Europe. References: (1) H. Kröber. Mitt. Biol. Bundesanst. Land Forstwirtsch. Berlin-Dahlem 225:73, 1985. (2) D. J. Stamps et al. 1990. Mycol. Pap. No. 162. CAB Int. Mycol. Inst., Kew, England.

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First Report of Trunk Canker and Gummosis of Kumquat Caused by Lasiodiplodia theobromae in China

Plant Disease ◽

10.1094/pdis-02-19-0424-pdn ◽

2020 ◽

Vol 104 (3) ◽

pp. 971-971

Author(s):

Qing Gui ◽

Jiang Zhao ◽

Zhihe Yu ◽

Wenxiu Sun ◽

Jianyou Mo ◽

...

Keyword(s):

Lasiodiplodia Theobromae ◽

First Report ◽

Trunk Canker

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First Report of Phytophthora cinnamomi on Quercus laurifolia

Plant Disease ◽

10.1094/pdis.2002.86.4.441d ◽

2002 ◽

Vol 86 (4) ◽

pp. 441-441 ◽

Cited By ~ 7

Author(s):

A. K. Wood ◽

F. H. Tainter

Keyword(s):

Phytophthora Cinnamomi ◽

Soil Extract ◽

Selective Medium ◽

Phytophthora Species ◽

Soil Samples ◽

Tissue Samples ◽

First Report ◽

Central Florida ◽

Oak Trees ◽

Length Width

In May 2001, bleeding cankers were observed on several laurel oak (Quercus laurifolia) trees in central Florida. Affected trees had chlorotic leaves, sparse canopies, and little new growth. Multiple cankers were present on the trunk and extended from the soil line up to approximately 5 m. Each canker had a reddish to dark brown or black exudate. From two of the infected trees, tissue samples were taken from beneath the bark around the edge of an actively growing lesion and transferred directly to Phytophthora-selective medium (1), and three soil cores (2 cm in diameter, 20 cm deep) were collected from the base of each tree. A baiting bioassay (with camellia leaf disks and shore juniper and eastern hemlock needles as baits) was used to assay fresh composite soil samples for Phytophthora species (1). P. cinnamomi was recovered from both tissue and soil samples (2). Mycelia were coralloid with abundant hyphal swellings. Sporangia were produced in 1.5% nonsterilized soil extract solution. Sporangia were ovoid to ellipsoid in shape and nonpapillate. Average sporangium size was 72 × 45 μm (length × width). To our knowledge, this is the first report of P. cinnamomi on laurel oak trees. References: (1) A. J. Ferguson and S. N. Jeffers. Plant Dis. 83:1129, 1999. (2) G. M. Waterhouse. Key to the species of Phytophthora de Bary. Mycol. Pap. 92. CMI. Kew, UK, 1963.

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First Report of Root and Crown Rot Caused by Phytophthora cinnamomi Affecting Native Stands of Arctostaphylos myrtifolia and A. viscida in California

Plant Disease ◽

10.1094/pdis.2003.87.11.1395b ◽

2003 ◽

Vol 87 (11) ◽

pp. 1395-1395 ◽

Cited By ~ 7

Author(s):

T. J. Swiecki ◽

E. A. Bernhardt ◽

M. Garbelotto

Keyword(s):

Sierra Nevada ◽

Native Species ◽

Phytophthora Cinnamomi ◽

Crown Rot ◽

Infested Soil ◽

Mixed Stands ◽

First Report ◽

Root And Crown Rot ◽

Dead Plant ◽

Natural Stands

Ione manzanita (Arctostaphylos myrtifolia) is a rare, endemic, evergreen shrub restricted to Ione formation soils (infertile, acidic, sedimentary oxisols) in the foothills of the Sierra Nevada. The widely distributed A. viscida (whiteleaf manzanita) intermixes with A. myrtifolia at the margins of Ione formation soils. In 2002, we observed extensive mortality within two mixed stands of A. myrtifolia and A. viscida near Ione, CA. At one site, nearly all plants of both species in a 0.25-ha area had died recently. At a second site, most of the A. myrtifolia and A. viscida plants on several hectares died at least 5 years earlier. Dying plants of both species exhibited wilting and desiccation of the foliage; dark brown discoloration and necrosis of the root crown, taproot, and some large roots; and loss of fine roots. Plants of all age classes were affected. We consistently isolated a Phytophthora sp. from symptomatic plants of both species using PARP (1) and acidified potato dextrose agar. We recovered the same Phytophthora sp. from soil collected under dead plants using green pears to bait flooded soil samples. The pathogen was not recovered from soil collected under healthy plants 50 m from the nearest dead plant. Based on the morphology of the hyphae, chlamydospores, sporangia, and the sequence of the internal transcribed spacer rDNA, we identified the pathogen as P. cinnamomi Rands (GenBank Accession No. AY267370; ATCC No. MYA-2989). To test pathogenicity, we poured zoospore suspensions (4 × 104 zoospores per pot) on the soil of eight pots with rooted A. myrtifolia cuttings and four pots with rooted A. viscida cuttings (1 14-month-old plant per pot). The soil in inoculated and uninoculated control pots (eight A. myrtifolia and two A. viscida) was flooded for 20 to 23 h. All inoculated A. myrtifolia developed severe root and crown rot, and seven of eight died within 17 days. All inoculated A. viscida developed severe root rot, and three of four developed 5- to 10-cm long basal cankers. After 17 days, we isolated P. cinnamomi from inoculated A. myrtifolia (eight of eight) and A. viscida (two of four) but not from controls, which remained healthy. We tested pathogenicity in native soil by transplanting rooted cuttings (eight A myrtifolia and six A. viscida) into pots of naturally infested soil from one of the disease centers. Controls (four and three plants, respectively) were planted in soil collected from under healthy plants. Pots were flooded for 12 to 13 h for 11 days (A. myrtifolia) or 6 weeks (A. viscida) after transplanting. All plants grown in naturally infested soil developed root and crown rot, and all A. myrtifolia and one A. viscida died within 5 weeks of transplanting. Plants grown in field soil collected near healthy plants remained asymptomatic. We isolated P. cinnamomi from all eight A. myrtifolia and three A. viscida plants grown in infested soil but not from the controls. To our knowledge, this is the first report of root and crown rot caused by P. cinnamomi on A. myrtifolia and A. viscida. P cinnamomi was first isolated in the state in 1942 (2), but it has not previously been reported to caused significant mortality in natural stands of California native species. This disease will significantly impact conservation of the already threatened A. myrtifolia. References: (1) D. C. Erwin and O. K. Ribeiro, Phytophthora Diseases Worldwide. American Phytopathological Society, St. Paul, MN 1996. (2) V. A. Wager. Hilgardia 14:519, 1942.

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First Report of Root Rot Caused by Pythium spiculum Affecting Cork Oaks at Doñana Biological Reserve in Spain

Plant Disease ◽

10.1094/pdis-10-12-0952-pdn ◽

2013 ◽

Vol 97 (7) ◽

pp. 991-991 ◽

Cited By ~ 1

Author(s):

P. De Vita ◽

M. S. Serrano ◽

C. Ramo ◽

C. Aponte ◽

L. V. García ◽

...

Keyword(s):

Root Rot ◽

Phytophthora Cinnamomi ◽

Quercus Suber ◽

First Report ◽

Root Necrosis ◽

Pathogenicity Tests ◽

Branch Dieback ◽

The University ◽

Virulence Group ◽

Biological Reserve

Cork oaks (Quercus suber L.) are key tree species at Doñana Biological Reserve (DBR), Huelva, Spain. Sampling was conducted on a total of 13 trees exhibiting symptoms of decline (foliar wilting and defoliation, branch dieback, and root necrosis). In 2008. Phytophthora cinnamomi was isolated from feeder roots of one tree and Pythium spiculum from two additional oaks. In 2011, both pathogens were isolated from six oaks, only P. cinnamomi from three oaks, and only Py. spiculum from one oak. This expansion was associated with high winter rainfall levels since 2009 that led to long periods of soil flooding. While P. cinnamomi is well known to cause a root disease on Q. suber (2), P. spiculum is a newly described species isolated from Quercus, Vitis, Prunus, Castanea, and Celtis species, but its pathogenicity was demonstrated only on Q. ilex (syn. Q. rotundifolia) (1). Pathogenicity tests were conducted on 4-year-old Q. suber plants. Inocula consisted of two isolates of Py. spiculum from DBR (DO8 and DO36 from Q. suber). For comparison with these, three isolates previously tested on Q. ilex (1) were included: two isolates of Py. spiculum, PA54 (from Q. suber) and PE156 (from Q. ilex); and one isolate of P. cinnamomi, PE90 (from Q. ilex). All these isolates came from the Andalucía region, stored at the oomycete collection of the University of Córdoba, and showed a 99 to 100% homology with their expected ITS sequences in GenBank (DQ196131 for Py. spiculum and AY943301 for P. cinnamomi). Inoculum was prepared by shaking and mixing propagule-bearing mycelium produced in carrot broth petri dishes (20°C, 4 weeks) in sterile water, to produce a concentration of 3 × 104 oospores × ml−1 (Py. spiculum) or 3 × 104 chlamydospores × ml−1 (P. cinnamomi). One hundred milliliters of inoculum was applied to each root (1). There were 10 inoculated plants per isolate and 10 non-inoculated control plants. All plants were waterlogged 2 days per week to favor root infection and maintained in an acclimatised greenhouse (12–28°C). Three months later, the inoculated plants showed symptoms of root necrosis that resulted in foliar wilting followed occasionally by defoliation. Control plants did not develop foliar symptoms nor root necrosis. Root damage severity assessed on a 0 to 4 scale (3) exhibited significant differences (P < 0.05) in relation to the control plants for all the isolates tested, with isolate PE90 (P. cinnamomi) and isolates PA54, DO8, and DO36 (P. spiculum) all averaging a root necrosis value of 2.5. Isolate PE156 of P. spiculum produced values of root necrosis (1.6 in average) significantly lower (P < 0.05) than the rest. This isolate belongs to the low virulence group of P. spiculum described on Q. ilex (1). The inoculated oomycete was always reisolated from necrotic roots and never from roots of control plants. To the best of our knowledge, this is the first report of P. spiculum as the cause of root rot of Q. suber. References: (1) Romero et al. J. Phytopathol. 155:289, 2007. (2) Sánchez et al. For. Pathol. 32:5, 2002. (3) Sánchez et al. For. Pathol. 35:115, 2005.

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First Report on an Infestation of Phytophthora cinnamomi in Natural Oak Woodlands of California and its Differential Impact on Two Native Oak Species

Plant Disease ◽

10.1094/pd-90-0685c ◽

2006 ◽

Vol 90 (5) ◽

pp. 685-685 ◽

Cited By ~ 21

Author(s):

M. Garbelotto ◽

D. Hüberli ◽

D. Shaw

Keyword(s):

Phytophthora Cinnamomi ◽

Direct Sequencing ◽

Internal Transcribed Spacer Region ◽

Dark Line ◽

Cold Temperatures ◽

Oak Woodlands ◽

First Report ◽

Agar Plug ◽

Average Maximum ◽

Coast Live Oaks

During an intense survey of natural woodlands around Lake Hodges (33°N, 117°W) in June 2001, symptoms typical of root and collar rot caused by Phytophthora spp. were observed on 27% of 474 coast live oaks (Quercus agrifolia Nee.) and on none of 86 Engelmann oaks (Q. engelmannii Greene), in spite of complete spatial intermixing of the two species. Symptoms on coast live oaks included viscous exudates emerging through intact bark matched by underbark dark lesions with irregular margins. Lesions were delineated by a dark line and present on the root collar or the buttress of symptomatic trees. Crowns of trees with lesions ranged from completely healthy to declining or dead. All symptomatic trees were in proximity of the lake or streams. Phytophthora cinnamomi Rands was isolated from four trees in three distinct sites by plating tissues from lesion margins on PARP selective medium and from four soil samples by using standard pear baiting and plating lesions from pear tissue onto PARP. Identification of the isolates was obtained from microscopic observations and direct sequencing of the internal transcribed spacer region of the rDNA (Genbank Accession Nos. AY302148, MC2 and AY302149, MC3). P. citricola Sawada was also isolated once. Pathogenicity tests were completed to compare the susceptibility of the two species of oaks growing in the Lake Hodges region with P. cinnamomi. Two P. cinnamomi isolates from Lake Hodges (MC2, ATCC MYA-3711; MC3) and one isolate from an avocado orchard in San Diego County (MC6) were used to inoculate separately 10 5-year-old trees each of Q. agrifolia and Q. engelmannii grown in 5-gallon containers. Inoculations were performed in two lath-house experiments during February and September 2002 by placing an 8-mm diameter V8-agar plug from the margin of a P. cinnamomi colony underbark and sealing the wound with Parafilm and grafting wax. Lesion lengths were measured 2 months after inoculation, and the presence of the pathogen confirmed by reisolation on PARP. Mean average, maximum, and minimum temperatures were 14, 19, and 9°C and 21, 24, and 18°C for the February and September inoculations, respectively. The February inoculation resulted in small lesions only on Q. agrifolia (26 ± 15 mm, SD). The September inoculation resulted in 135 ± 68 mm (SD) lesions on Q. agrifolia and 49 ± 35 mm (SD) lesions on Q. engelmannii. Controls did not show any lesions. The length of lesions was significantly different between the two hosts (P < 0.0001) and significant differences were observed among the three isolates (P = 0.0018). Although Q. agrifolia is a known host for P. cinnamomi in California (2,3), to our knowledge, this is the first report of widespread infestation of P. cinnamomi in natural oak woodlands in the western United States. Survey and inoculation results indicated Q. engelmannii to be less susceptible to infection. Inoculation results confirm previous research that cold temperatures are unfavorable to this pathogen and isolates differed in pathogenicity toward Q. agrifolia. Decline of oaks infected by P. cinnamomi was observed only in conjunction with other factors, in particular with the presence of the oak twig girdler, Agrilus angelicus Horn., an insect favored by stress conditions such as drought. Similar effects have been reported for Mediterranean oaks infected by the same pathogen (1). References: (1) C. M. Brasier. Nature 360:539, 1992. (2) P. A. Miller. Western Shade Tree Conf. Proc. 8:39, 1941. (3) S. M. Mircetich et al. Plant Dis. Rep. 61:66, 1977.

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