Die-Back Tolerance in Eucalypt Species in Relation to Fertilization and Soil Populations of Phytophthora cinnamomi

1973 ◽  
Vol 21 (1) ◽  
pp. 53 ◽  
Author(s):  
GC Marks ◽  
FY Kassaby ◽  
PC Fagg
Keyword(s):  
Population Density ◽  
Phytophthora Cinnamomi ◽  
Growth Responses ◽  
Coastal Forests ◽  
Visible Injury ◽  
Infection Pattern ◽  
Eucalypt Species ◽  
Soil Temperatures ◽  
High Hazard ◽  
Hazard Rating

The die-back tolerance of 16 fertilized (17/9/7 nitrogen-phosphorus-potassium) and unfertilized eucalypt and two conifer species was tested in the coastal forests of east Gippsland on sites rated as of "high", "moderate", and "low" hazard on the basis of previous damage, internal soil drainage, and infection by P. cinnamomi. Measurements were made of the population density index (PDI) of P. cinnamomi, of soil moisture, and of soil temperature. Supporting greenhouse and laboratory experiments are also reported. The high hazard site showed the most uniform infection and the greatest PDI, the low hazard site the least uniformity in the infection pattern. During the first year's growth, five renantherous eucalypt species showed considerable sensitivity to root rot and die-back; the intensity of the disease and the number of deaths were directly proportional to the hazard rating of the sites. The 11 species of Macrantherae tested were very tolerant to die-back. The disease was aggravated by temporary waterlogging during a 7 day period, but waterlogging did not cause die-back. The disease first appeared in the plots when soil temperatures rose above 15°C. Greenhouse tests showed that P. cinnamomi was most virulent at 22°, and visible injury became evident between 15 and 18°. Fertilizers produced striking growth responses during the first year in both subgenera of eucalypts on the low hazard site, with only minor differences between the two groups. Similar responses were seen only on the Macrantherae on the moderate and high hazard sites. The growth of the surviving renantherous eucalypts was uneven, and fertilizers greatly increased their sensitivity to die-back disease. The response to fertilization in both subgenera was directly related to the disease hazard of the site and the intensity of infection by P. cinnamomi. Differences in response to fertilization between the Macrantherae and the Renantherae were directly proportional to the population density and distribution of P. cinnamomi in the soils. The initial tolerance to die-back of the two conifers, Pinus radiata and P. Elliotii, was similar to that of the most resistant macrantherous eucalypts tested.

Variation in Population Levels of Phytophthora cinnamomi in Eucalyptus Forest Soils of Eastern Victoria

1975 ◽  
Vol 23 (3) ◽  
pp. 435 ◽  
Author(s):  
GC Marks ◽  
FY Kassaby ◽  
PC Fagg
Keyword(s):  
Soil Temperature ◽  
Root Rot ◽  
Forest Cover ◽  
Phytophthora Cinnamomi ◽  
Seasonal Fluctuation ◽  
Bare Soil ◽  
Canopy Closure ◽  
Coastal Forests ◽  
Eucalyptus Forest ◽  
Eucalypt Species

The behaviour of Phytophthora cinnamomi Rands was examined over a 2 year period on newly cleared and replanted eucalypt sites in the coastal forests of eastern Gippsland, rated as of low, moderate and high die-back hazard in relation to the drainage and disease characteristics of the original forest cover and surrounding trees. The fungus behaved like a saprophytic survivor. Maximum population levels, assessed as a 'population density index' (PDI), occurred within the soil influenced directly by the root mass. The PDI in adjacent bare soil was very low. The PDI depended, inter alia, on fungal pathogenesis, soil temperature and soil moisture. Mean maximum PDI values recorded respectively for the high, moderate and low hazard sites were in the ratio of about 8/4/1. This ratio was directly related to the depth of the clay pan beneath the surface. There was a marked seasonal variation in PDI, most pronounced on the high hazard site and least on the low hazard site. The minimum and maximum values were recorded in June (winter) and December-March (summer) respectively. Moderately heavy rainfall had little effect on the PDI in well-drained soils, even during midsummer when soil temperatures were optimum for fungal populations to increase. Fire affected PDI values only temporarily. PDI values in the surface soil were greater than at a depth of 75 cm, and the distribution of the fungus through the soil profile was influenced by soil texture. Before canopy closure occurred, PDI values were greater under eucalypt species tolerant to root rot than under sensitive species. Canopy closure reduced the seasonal fluctuation in soil temperature and, on sites where tree growth was vigorous, the reduction in PDI was striking. Addition of fertilizers to the soil had no direct effect on the PDI, the reduction observed being an indirect effect produced possibly by accelerated growth, increased transpiration and rapid canopy closure. These results suggest that root rot-sensitive eucalypt species growing on coastal sites with impeded drainage will prove vulnerable to die-back, and that any form of logging activity that reduces the amount of green cover on infected sites will aggravate root rot if the fungus is present. Consequently it will not be possible to manage these stands by conventional methods. On steeper, well-drained sites the disease should not prove to be a serious hazard except in exceptionally wet summer and autumn periods.

The Distribution of Phytophthora cinnamomi in forests of Eastern Gipsland, Victoria

1975 ◽  
Vol 23 (2) ◽  
pp. 263 ◽  
Author(s):  
GC Marks ◽  
PC Fagg ◽  
FY Kassaby
Keyword(s):  
Phytophthora Cinnamomi ◽  
New South ◽  
Coastal Forests ◽  
Soil Drainage ◽  
Factors Affecting ◽  
South Wales ◽  
Number Of Factors ◽  
Soil Temperatures ◽  
Eucalypt Forests ◽  
Soil Surveys

Soil surveys of the distribution of Phytopthora cinnamomi in eastern Victorian eucalypt forests showed it to be widely distributed in flat, poorly drained coastal forests extending from Wilson's Promontory to the New South Wales border and from 15 to 25 km from the coast. P. cinnamomi was scattered in the foothill forests up to an altitude of about 800 m. It was sometimes found in high altitude forests, at sites where recent logging, clearing and road con- struction had occurred. Its frequency of occurrence was related to the intensity of forestry activity, to internal soil drainage and to the occurrence of warm soil temperatures. Data are provided on a number of factors affecting soil populations of P. cinnamomi, and its possible origin is discussed.

Development of Phytophthora cinnamomi Infection in Roots of Eucalypt Species Growing in a Soil That Suppresses Phytophthora Root Disease

1983 ◽  
Vol 31 (3) ◽  
pp. 239 ◽  
Author(s):  
GC Marks ◽  
IW Smith
Keyword(s):  
Inner Core ◽  
Phytophthora Cinnamomi ◽  
Sandy Loam ◽  
Seedling Survival ◽  
Genetic Resistance ◽  
Coarse Sand ◽  
Root Disease ◽  
Phenotypic Resistance ◽  
Eucalypt Species ◽  
Core Soil

When Eucalyptus sieberi was grown in either a steamed or unsteamed krasnozem that suppressed Phytophthora cinnamomi root rot and repotted when either 6 or 12 weeks old in a larger container of inoculated sandy loam, seedling survival was significantly greater in the unsteamed treatments. By varying the treatments in the inner core soil and outer inoculum jacket, substituting a biologically inert coarse sand in place of the krasnozem in the core, and using eucalypt species of varying disease tolerance while maintaining very strict hygiene conditions throughout these experiments, it was possible to either demonstrate or deduce that: (a) the seedlings were killed when infection spread into the major roots, root collar and lower stem; (b) the microflora in the unsteamed krasnozem appeared to slow down the decay process within the root, possibly when the fungus was attempting to establish itself within the root; (c) the phenotypic resistance of a seedling to root disease depended, inter alia, on its genetic resistance and on the microflora in the surrounding soil; (d) once the fungus was established in the suberized tissues the microflora in the external environment had no influence on disease.

A Method of Hazard-Rating White Spruce Plantations For Yellowheaded Spruce Sawfly Defoliation

1986 ◽  
Vol 3 (3) ◽  
pp. 104-105 ◽  
Author(s):  
Bruce W. Morse ◽  
Herbert M. Kulman
Keyword(s):  
White Spruce ◽  
Management Plan ◽  
Aerial Photographs ◽  
Slope Aspect ◽  
Final Model ◽  
North Central ◽  
Site Characteristics ◽  
High Hazard ◽  
Rating Model ◽  
Hazard Rating

Abstract A hazard-rating model for defoliation by the yellowheaded spruce sawfly was developed and validated using 25 white spruce plantations in north central Minnesota. The dependent variable was degree of defoliation, and the independent variables, as measured from small-format aerial photographs, were steepness and slope aspect. The site characteristics and defoliation were correlated using a maximum likelihood logistic regression. The final model determined that steep, south-facing slopes had the highest probability of sawfly-caused defoliation. Identification of high-hazard sites should be a major component of a management plan for this pest. North. J. Appl. For. 3:104-105, Sept. 1986.

scholarly journals Principal Factors Influencing Tree Growth in Low-Lying Mid Atlantic Coastal Forests

Forests ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1351
Author(s):  
LeeAnn Haaf ◽  
Salli F. Dymond ◽  
Danielle A. Kreeger
Keyword(s):  
Loblolly Pine ◽  
Tree Growth ◽  
Partial Correlation ◽  
Coastal Flooding ◽  
Growth Patterns ◽  
Water Levels ◽  
Growth Responses ◽  
Coastal Forests ◽  
Flood Exposure ◽  
Correlation Tests

Flood frequencies in coastal forests are increasing as sea level rise accelerates from 3–4 mm year−1 to possibly more than 10 mm year−1 by the end of this century. As flooding increases, coastal forests retreat, ghost forests form, and coastal marshes migrate inland. The existence of ghost forests makes the mechanism of forest retreat clear: low-lying trees become more exposed to coastal flooding until they ultimately die. Variability in these retreat rates, however, makes it difficult to predict where and when retreat will continue to occur. Understanding tree growth responses to tidal water levels relative to other environmental factors is a critical step in elucidating the factors that influence retreat variability. Here, dendrochronology was used to study factors that contribute to variations in growth patterns in four coastal forests fringing the Delaware and Barnegat Bays. Species chosen for study included loblolly pine (Pinus taeda), pitch pine (Pinus rigida), and American holly (Ilex opaca). Pearson’s and partial correlation tests showed that growth relationships with monthly environmental conditions varied across sites and were moderate in strength (generally R < 0.5), but each site had at least one significant growth-water level correlation. As coastal flooding exposure is spatially dependent, tree chronologies were also separated into high and low elevation groups. Pearson’s and partial correlation tests of the mean differences between elevation groups showed that at some sites, low elevation trees grew less than high elevation trees when water levels were high, as might be expected. At one site, however, lower elevation trees grew more when water levels were higher, which suggests that other interacting factors—regardless of current flood exposure—potentially have positive, yet likely temporary, influence over tree growth in these low-lying areas.

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.

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.

Population Dynamics of Crenate Broomrape (Orobanche crenata) in Faba Bean (Vicia faba)

Weed Science ◽  
1993 ◽  
Vol 41 (4) ◽  
pp. 563-567 ◽  
Author(s):  
Francisca Lopez-Granados ◽  
Luis Garcia-Torres
Keyword(s):  
Growth Rate ◽  
Population Dynamics ◽  
Population Density ◽  
Population Growth ◽  
Faba Bean ◽  
Population Growth Rate ◽  
Spatial Dispersion ◽  
Climatic Conditions ◽  
Orobanche Crenata ◽  
Soil Temperatures

Progression of crenate broomrape population density (PD, number of emerged plants m-2) in faba bean was studied over 8 yr in Spain. Spatial dispersion and effect of climatic conditions on parasite population growth rate (PGR) also were studied. With repeated cropping of faba bean, infestations of crenate broomrape increased from an initial PD of 0.15 to an average of 26, with a maximum of about 40 to 45. The average population growth rate (PGR, ratio between the PD of any 2 consecutive years) was approximately 3. However, this figure varied widely among localities and years, from 0.8 to 7.7. A highly significant relationship (P = 0.01) was found between PGR and rainfall and soil temperatures during December to February, months of crop vegetative growth. Dispersion of crenate broomrape infestations mainly followed direction of crop rows, most likely due to the effect of tillage and harvesting operations, which were the same direction as sowing.

Association of Phytophthora cinnamomi With Pinus radiata in South Australia

1981 ◽  
Vol 29 (1) ◽  
pp. 11 ◽  
Author(s):  
M Bumbieris
Keyword(s):  
Soil Moisture ◽  
Population Density ◽  
Pinus Radiata ◽  
Phytophthora Cinnamomi ◽  
South Australia ◽  
Pine Forest ◽  
Forest Plantation ◽  
Root Zones ◽  
High Soil Moisture ◽  
High Soil

In a pine forest plantation, P. cinnamomi was rarely isolated from the root zones, and never from the roots, of established P. radiata growing at P. cinnamomi sites. When a P. cinnamomi site was replanted with P. radiata, a third of the young pines died during the first 9 months, about 50% of them yielding P. cinnamomi from roots. Death of the trees followed an increase in the soil population density of P. cinnamomi which appeared to be correlated with increasing soil temp. and high soil moisture.

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