Phytophthora cinnamomi in the Brisbane Ranges: Patterns of Disease Extension

1976 ◽  
Vol 24 (2) ◽  
pp. 201 ◽  
Author(s):  
G Weste ◽  
P Ruppin ◽  
K Vithanage
Keyword(s):  
Environmental Factors ◽  
Phytophthora Cinnamomi ◽  
Soil Characteristics ◽  
Drainage Water ◽  
Sclerophyll Forest ◽  
Disease Extension ◽  
Wavy Boundary ◽  
Active Disease

Three patterns of disease extension were observed in areas of uncultivated shrubby dry sclerophyll forest invaded by the pathogen Phytophthora cinnamomi. Environmental factors were found to determine which pattern developed. Where inoculum was spread downhill with drainage water, diseased areas were separated by clearly defined boundaries from unaffected vegetation. Where disease extension occurred uphill through soil or from root to root, a wavy boundary marked the active disease front. Investigations showed that absence of disease extension for 4 years in highly susceptible vegetation may be associated with differences in soil characteristics.

Phytophthora cinnamomi: Population Densities in Forest Soils

1977 ◽  
Vol 25 (5) ◽  
pp. 461 ◽  
Author(s):  
G Weste ◽  
P Ruppin
Keyword(s):  
Environmental Factors ◽  
Soil Water ◽  
Phytophthora Cinnamomi ◽  
Soil Water Potential ◽  
Forest Community ◽  
Population Densities ◽  
Sclerophyll Forest ◽  
Soil Temperatures ◽  
Disease Extension ◽  
Pathogen Populations

Population densities of Phytophthora cinnamomi, associated disease and environmental factors were studied concurrently during a 2-year period in three different forest ecosystems. Pathogen populations showed seasonal variation, low values being obtained for winter months associated with soil temperatures less than 10°C. Populations increased with warmer temperatures for spring and summer, but declined during dry periods in late summer or early autumn when the soil water potential was lower than -9 bars, although at that period soil temperatures were favourable. High populations were recorded in autumn, then declined with decrease in soil temperatures during winter. Correlation coefficients indicated a highly significant relationship between pathogen populations and soil temperatures from autumn to early summer, and between soil moisture and pathogen population for summer and autumn, in the Brisbane Ranges independently of site. The same pattern was evident in wetter forests at Narbethong and savannah woodlands at Wilson's Promontory, although results were not significant. Disease was evident wherever the pathogen occurred among susceptible hosts. The savannah woodland, the dry shrubby sclerophyll forest and the wetter sclerophyll forest all contained susceptible dominants; consequently disease was associated with changes in the forest community such as early death of the understorey, later die-back and death of the trees, and an increase in sedges and in bare ground. Symptoms and deaths increased with time from invasion. The severity of disease and its rate of extension, apart from spread by free water, were associated with environmental factors such as shallow soil, poor drainage and low soil water-holding capacity. These were characteristic of the Brisbane Ranges, where destruction of the forest community was severe and the rate of disease extension rapid. In the deep krasnozem at Narbethong and the deep sands of Wilson's Promontory, destruction was confined to the most susceptible hosts, disease extension was continuous but slow, and deaths occurred in a mosaic throughout the infected zone.

Field Resistance in Three Native Monocotyledon Species That Colonize Indigenous Sclerophyll Forest After Invasion by Phytophthora cinnamomi

1984 ◽  
Vol 32 (4) ◽  
pp. 339 ◽  
Author(s):  
D Phillips ◽  
G Weste
Keyword(s):  
Phytophthora Cinnamomi ◽  
Lateral Roots ◽  
Fungal Growth ◽  
Field Resistance ◽  
Root Production ◽  
Root Tip ◽  
Bare Ground ◽  
Rapid Reduction ◽  
Sclerophyll Forest ◽  
Disease Extension

Lepidosperma laterale (Cyperaceae), Gahnia radula (Cyperaceae) and Poa sieberana (Poaceae) colonize bare ground of dry sclerophyll forest after disease due to P. cinnamomi. To determine their resistance, plants grown in divided root boxes were inoculated with 150-200 zoospores of the pathogen. Infected roots ceased growth. In the small necrotic lesions produced, the pathogen remained viable and capable of providing a source of inoculum for disease extension. Fungal growth was usually limited to the lesion but in some cases a few hyphae were observed in adjacent tissue. Away from the lesion there was a rapid reduction of fungal material and of the associated cellular disintegration. Rates of root production and root growth were not stimulated by infection but uninfected lateral roots replaced the root tip in some plants; in others, a new root tip emerged from the necrotic zone, enabling the plant to outgrow the fungal attack.

Vegetation Changes as a Result of Invasion of Forest on Krasnozem by Phytophthora cinnamomi

1980 ◽  
Vol 28 (2) ◽  
pp. 139 ◽  
Author(s):  
G Weste
Keyword(s):  
Pinus Radiata ◽  
Phytophthora Cinnamomi ◽  
First Year ◽  
Acacia Dealbata ◽  
Sclerophyll Forest ◽  
Lower Height ◽  
Leaf Spot Fungus ◽  
Future Status ◽  
Reduced Water ◽  
Increased Susceptibility

Disease caused by Phytophthora cinnamomi was studied for 5 years in native and planted forest growing on krasnozem in the northern foothills of the Great Dividing Range at Narbethong, 100 km northwest of Melbourne. Changes in species composition were recorded for three sites carrying mature dry sclerophyll forest of Eucalyptus obliqua and Eucalyptus radiata, young plantations of E. obliqua, and young plantations of Pinus radiata. The mature ecualypts were diseased in 1974 and now are gradually dying. The young E. obliqua showed greater resistance than the older trees to the pathogen but infected trees were characterized by lower height, small leaves with reduced water potential, and an increased susceptibility to the leaf spot fungus Aulographina eucalypti. Susceptible understorey species such as Tetratheca ciliata and Epacris impressa died, but seedling regeneration of these has since occurred on one site. No species has disappeared from all three sites but T. ciliata and Daviesia latifolia almost disappeared from site 2, and the total number of plants was reduced. Species such as Leptospermum juniperinum and Platylobium formosum developed fluctuating cycles of chlorosis and die-back followed by either recovery or death. Resistant plants such as sedges, grasses and Acacia dealbata invaded the diseased forest. During the first year of the investigation 13% of the 4-year-old Pinus radiata died, but this particular site was well drained, warmer and drier than the others and the surviving pines later grew vigorously and crowded out other species. Symptoms are no longer evident on this site. The future status of the mature forest and the probable effects of disease on the young E. obliqua plantation are discussed.

Regeneration of Vegetation in the Brisbane Ranges After Fire and Infestation by Phytophthora cinnamomi

1985 ◽  
Vol 33 (1) ◽  
pp. 15 ◽  
Author(s):  
P Dawson ◽  
G Weste ◽  
D Ashton
Keyword(s):  
Population Density ◽  
Seed Production ◽  
Phytophthora Cinnamomi ◽  
Basal Area ◽  
First Record ◽  
Inoculum Density ◽  
Crown Cover ◽  
Bush Fire ◽  
Crown Density ◽  
Sclerophyll Forest

The distribution, population density and regeneration of some prominent spp. of understorey and overstorey (dominant Eucalyptus spp.) were monitored over a period of 20 yr in seasonally well drained dry sclerophyll forest. Changes varied with susceptibility to the pathogen and to fire. Changes in spp. composition and crown density of the overstorey were attributed to fire. Population density, basal area and crown cover of the Eucalyptus spp. which were associated with the pathogen, also declined in 1962-82. Both distribution and population density of Xanthorrhoea australis and Isopogon ceratophyllus declined markedly following the spread of infestation, whereas those of Hakea sericea and Lepidosperma semiteres increased. Regeneration of X. australis but not of I. Ceratophyllus was observed in certain areas of the infested plots 12-20 years after infection. This is the first record of such regeneration. It is postulated that a bush fire in 1967 both stimulated X. australis seed production and reduced further an already declining pathogen inoculum density.

Susceptibility of Plant Species in Eucalyptus marginata Forest to Infection by Phytophthora cinnamomi

1995 ◽  
Vol 43 (1) ◽  
pp. 113 ◽  
Author(s):  
BL Shearer ◽  
M Dillon
Keyword(s):  
Plant Species ◽  
Phytophthora Cinnamomi ◽  
Eucalyptus Marginata ◽  
Number Of Species ◽  
Adjacent Soil ◽  
Cross Tabulation ◽  
Forest Plant Species ◽  
Active Disease ◽  
Active Centres

Estimates of the susceptibility of plant species of Eucalyptus marginata forest to Phytophthora cinnamomi were obtained by determining the frequency of plant death and isolation of the pathogen from plants occurring in disease centres in the forest. Plant species were assessed and sampled in 63 active disease centres and 17 old centres infested with P. cinnamomi in E. marginata forest north of the Preston River, south-westem Australia. Impact of P. cinnamomi was intermediate (scattered deaths) in 46% of active disease centres and high (most susceptible plants dead) in 29% of active centres. Impact in 65% of old disease centres was high. Dicotyledons (Magnoliidae) out-numbered monocotyledons (Liliidae). Just over half of the species were from six Magnoliidae families with the largest number of species from the Papilionaceae and Proteaceae. The greatest number of species within the Liliidae were consistently from Haemodoraceae. Families in which species tended not to die in disease centres were mainly from the Papilionaceae, Proteaceae, Mimosaceae, Myrtaceae, Dilleniaceae, Apiaceae and Goodeniaceae for the Magnoliidae and Cyperaceae and Haemodoraceae for the Liliidae. The species which tended to die frequently in disease centres were mainly from the Magnoliidae families: Papilionaceae, Proteaceae and Epacridaceae; and the Liliidae family Xanthorrhoeaceae, as well as the only species of the Zamiaceae. Phytophthora cinnamomi was isolated from 38 of the 105 species occurring in three or more active disease centres, but from only 17 of the 107 species occurring in old centres. For most species in active disease centres, the frequency of isolation of P. cinnamomi from plants was much less than the frequency of recently dead plants sampled. Isolation from plants was less frequent than from adjacent soil. The pathogen was isolated from plant or soil mainly for species of the Papilionaceae, Proteaceae, Epacridaceae and Dilleniaceae of the Magnoliideae and the Iridaceae and Xanthorrhoeaceae of the Liliidae. Cross tabulation of species by frequency of death and isolation of P. Cinnamomi from plant and soil provided the opportunity to classify the response of plant species to infection by P. cinnamorni.

The invasion of native forest by Phytophthora cinnamomi. I. Brisbane Ranges, Victoria

1971 ◽  
Vol 19 (3) ◽  
pp. 281 ◽  
Author(s):  
GM Weste ◽  
P Taylor
Keyword(s):  
Water Stress ◽  
Phytophthora Cinnamomi ◽  
Eucalyptus Species ◽  
Native Forest ◽  
Symptom Expression ◽  
Root Pathogen ◽  
Disease Symptoms ◽  
Sclerophyll Forest ◽  
Drainage Channels

Disease within an open sclerophyll forest dominated by Eucalyptus species of relatively low stature (15-20 m) was shown to be caused by Phytophthora cinnamomi Rands, an introduced root pathogen. Diseased sites were mapped and measured. The rate of advance of the pathogen over a period of 5 months was calculated at 4 m per month through moderately drained soils compared with 7 m per month through soils subject to waterlogging. Areas showing disease symptoms increased from 10.8 to 90%, the major extensions occurring along gullies. Spread of the fungus was associated with road-making activities, waterlogging, and the presence of drainage channels. Symptom expression in the different species was studied and shown to be similar to that associated with water stress. Most of the 42 species comprising the woody flora were susceptible to the disease, those particularly susceptible including the dominants. During a period of 8 months mortalities occurred in 50% of the species. Grasses, sedges, and Eucalyptus goniocalyx appeared to be field-resistant, but were uncommon in the Aora of the sites studied.

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