Mean Defoliation Research Articles

European-wide forest monitoring substantiate the neccessity for a joint conservation strategy to rescue European ash species (Fraxinus spp.)

European ash (Fraxinus excelsior) and narrow-leafed ash (F. angustifolia) are keystone forest tree species with a broad ecological amplitude and significant economic importance. Besides global warming both species are currently under significant threat by an invasive fungal pathogen that has been spreading progressively throughout the continent for almost three decades. Ash dieback caused by the ascomycete Hymenoscyphus fraxineus is capable of damaging ash trees of all age classes and often ultimately leads to the death of a tree after years of progressively developing crown defoliation. While studies at national and regional level already suggested rapid decline of ash populations as a result of ash dieback, a comprehensive survey at European level with harmonized crown assessment data across countries could shed more light into the population decline from a pan-European perspective and could also pave the way for a new conservation strategy beyond national boarders. Here we present data from the ICP Forests Level I crown condition monitoring from 27 countries resulting in > 36,000 observations. We found a substantial increase in defoliation and mortality over time indicating that crown defoliation has almost doubled during the last three decades. Hotspots of mortality are currently situated in southern Scandinavia and north-eastern Europe. Overall survival probability after nearly 30 years of infection has already reached a critical value of 0.51, but with large differences among regions (0.20–0.86). Both a Cox proportional hazard model as well as an Aalen additive regression model strongly suggest that survival of ash is significantly lower in locations with excessive water regime and which experienced more extreme precipitation events during the last two decades. Our results underpin the necessity for fast governmental action and joint rescue efforts beyond national borders since overall mean defoliation will likely reach 50% as early as 2030 as suggested by time series forecasting.

Assessment of Atmospheric Deposition and Vitality Indicators in Mediterranean Forest Ecosystems

Considering the fragility of the Mediterranean environment, there is an increasing need to improve the knowledge of this forest environment. The aim of this study was to examine the effects of air pollution on the forest ecosystem’s condition by analyzing tree vitality. The study area was chosen to represent the most important and the most common species in Mediterranean forest ecosystems of the Eastern Adriatic coast. Quercus pubescens, Quercus ilex, Pinus halepensis, and Pinus nigra plots were equipped with rain collectors and dendrometer bands. Sampling, measurements, and analyses of atmospheric deposition, foliar nutrient, defoliation, and growth were all carried out. Results showed that actual N deposition loads were the lowest in Aleppo pine forest and the highest in holm oak forests. This, however, did not have an effect on the concentrations of N in foliage. Most elements’ concentrations were in the plausible range. No relevant differences in mean defoliation between the plots were observed. The plots with a lower percentage of basal area increment (BAI%) were found to have lower defoliation. The research was conducted to bridge the gap in the knowledge of air pollutants and vitality indicators in different forest types. These findings are a valuable contribution to the sustainable forest management of Mediterranean forest.

Spatial-Temporal Patterns of Spruce Budworm Defoliation within Plots in Québec

We investigated the spatial-temporal patterns of spruce budworm (Choristoneura fumiferana (Clem.); SBW) defoliation within 57 plots over 5 years during the current SBW outbreak in Québec. Although spatial-temporal variability of SBW defoliation has been studied at several scales, the spatial dependence between individual defoliated trees within a plot has not been quantified, and effects of defoliation level of neighboring trees have not been addressed. We used spatial autocorrelation analyses to determine patterns of defoliation of trees (clustered, dispersed, or random) for plots and for individual trees. From 28% to 47% of plots had significantly clustered defoliation during the 5 years. Plots with clustered defoliation generally had higher mean defoliation per plot and higher deviation of defoliation. At the individual-tree-level, we determined ‘hot spot trees’ (highly defoliated trees surrounded by other highly defoliated trees) and ‘cold spot trees’ (lightly defoliated trees surrounded by other lightly defoliated trees) within each plot using local Getis-Ord Gi* analysis. Results revealed that 11 to 27 plots had hot spot trees and 27% to 64% of them had mean defoliation <25%, while plots with 75% to 100% defoliation had either cold spot trees or non-significant spots, which suggested that whether defoliation was high or low enough to be a hot or cold spot depended on the defoliation level of the entire plot. We fitted individual-tree balsam fir defoliation regression models as a function of plot and surrounding tree characteristics (using search radii of 3–5 m). The best model contained plot average balsam fir defoliation and subject tree basal area, and these two variables explained 80% of the variance, which was 2% to 5% higher than the variability explained by the neighboring tree defoliation, over the 3–5 m search radii tested. We concluded that plot-level defoliation and basal area were adequate for modeling individual tree defoliation, and although clustering of defoliation was evident, larger plots were needed to determine the optimum neighborhood radius for predicting defoliation on an individual. Spatial autocorrelation analysis can serve as an objective way to quantify such ecological patterns.

Evaluating the influence of varying levels of spruce budworm defoliation on annualized individual tree growth and mortality in Maine, USA and New Brunswick, Canada

Spruce budworm (SBW; Choristoneura fumiferana (Clem.)) defoliation can cause severe growth reduction and mortality to spruce-fir (Picea-Abies) species in eastern North America. Consequently, it is important to understand and predict how individual trees respond to defoliation in terms of growth and mortality. To address this, species- and region-specific individual-tree models quantifying the effects of cumulative defoliation on annualized diameter and height increment, crown recession, and mortality were developed using data from an extensive network of 424 and 136 permanent sample plots in Maine, USA and New Brunswick, Canada, respectively, during the last SBW outbreak of 1970–1990s. In general, these models fit well with relatively small bias despite large variation observed in the data. The effects of SBW defoliation on diameter increment, crown recession, and mortality were highly significant but relatively moderate depending on species, possibly because overall mean defoliation was rather moderate. Reduction in diameter increment and increase in mortality were always more significant for balsam fir (Abies balsamea L.) than for the spruce species. However, diameter increment returned to higher rates irrespective of species in New Brunswick, where the data were collected towards the end of the SBW outbreak. Overall, the results highlight the variability of tree response to SBW defoliation and the array of factors that may influence it.

Influence of soil and topography on defoliation intensity during an extended outbreak of the common pine sawfly (Diprion pini L.)

Abstract: Insect herbivore disturbances are likely to intensify as a consequence of climate change. In Finland, outbreaks of the common pine sawfly (Diprion pini L.), which feeds on Scots pine (Pinus sylvestris L.) needles, and resulting damage to forests have already increased. Although drivers of sawfly outbreak dynamics have been investigated, the effects of topography and soil fertility have not been fully elucidated. We studied the effect of elevation, slope and soil properties (carbon and nitrogen contents, C/N ratio, pH, texture and horizon thicknesses) on the defoliation intensity of 28 plots (227-531 m2), located in a 34.5 km2 forested area in eastern Finland suffering from an extended outbreak of D. pini. Plot elevation and slope (relative relief 35 m, maximum elevation 200 m a.s.l.) were derived from a digital elevation model and the soil properties from samples of the humus layer (Of+Oh), (Ah+)E and B horizons of podzol profiles. Defoliation was greater on the more fertile and flatter sites than on less fertile and steeper sites, but independent of elevation. The soil property most strongly correlated to plot mean defoliation was the C/N ratio of the humus layer (Spearman’s ρ = -0.68). However, logistic modelling showed that the thickness of the (Ah+)E-horizon had the highest classification accuracy in predicting the probability of a plot having moderate to severe (>20%) defoliation. Our study showed that forest damage caused by D. pini was related to topography and soil fertility. Taking these factors into account could help in understanding the population dynamics of D. pini, in modeling of insect outbreaks and in forest management planning.

Invasive plant Alternanthera philoxeroides suffers more severe herbivory pressure than native competitors in recipient communities.

Host-enemy interactions are vital mechanisms that explain the success or failure of invasive plants in new ranges. We surveyed the defoliation of invasive Alternanthera philoxeroides and co-occurring native plants on two islands during different seasons over three consecutive years and measured the leaf nitrogen content and the C/N ratio of each plant species. To evaluate the effects of herbivory on A. philoxeroides, an herbivore exclosure experiment was conducted. We found that the mean defoliation of A. philoxeroides was higher than that of native plants, regardless of whether the dominant species was A. philoxeroides or native plants. A. philoxeroides defoliation increased significantly as the months progressed, whereas the defoliation of the total population of native plants was constant. The leaf nitrogen content was positively correlated with defoliation, and it was highest in A. philoxeroides. Additionally, A. philoxeroides in the herbivore exclusion treatment showed an increase in shoot biomass and total shoot length. Our study revealed that native generalist herbivores prefer the invasive plant to the natives because of the higher leaf nitrogen content. These results support the biotic resistance hypothesis, suggesting that native herbivore species can limit the population spread of invasive plants.

Defoliation by gypsy moths negatively affects the production of acorns by two Japanese oak species

This study showed the negative effects of insect defoliation on the reproduction of canopy trees, where defoliation was not artificially manipulated but rather observed in a natural setting. The gypsy moth (Lymantria diapar) is a serious defoliator with the ability to completely defoliate forest canopies. Although the negative effects of defoliation on tree reproduction have been revealed in studies with artificially manipulated defoliation, few studies have examined the effect of insect defoliation on the reproduction of canopy trees under natural condition. In this study, visual surveys were used to clarify the effect of gypsy moth defoliation on the production of acorns by oaks (Quercus spp.). Surveys were conducted in an outbreak year at 22 sites in central Japan (13 sites with Quercus crispula and nine sites with Q. serrata). Five of the Q. crispula sites were severely defoliated (mean defoliation ranged from 67 to 88 %), while the remainder of the Q. crispula sites and all of the Q. serrata sites were lightly defoliated (0–20 %). A negative effect of gypsy moth defoliation on acorn production was detected for Q. crispula. However, there was a synchronous decrease in acorn production from the previous year and crop levels were low at all sites regardless of the defoliation severity. The consistent low crop levels were likely the result of weather-related factors. Defoliation also negatively affected the production of acorns for Q. serrata; however, severe defoliation was not present at any Q. serrata sites. This study suggests that insect defoliation can affect forest ecosystem processes, such as the regeneration of host trees and the behavior of wildlife that depend on seed production, by reducing the reproductive potential of host trees.

Occurrence of Erysiphe alphitoides in oak stands affected by flood disaster

Abstract Pedunculate oak (Quercus robur L.) is the most valuable deciduous tree species in Poland. For almost 30 years, an oak decline resulting from stress factors leading to a decrease of tree vitality in the long-term has been observed. The aim of the present study was to determine the proportion of leaves infected by the fungus Erysiphe alphitoides, the cause of powdery mildew, in post-flood oak stands situated in the Forest District Wołów (51°32’N, 16°62’E) as well as to evaluate effects of powdery mildew with respect to the oak decline. In order to record the powdery mildew incidence, we selec ted three trees in each of the ten investigated oak stands, and 200 leaves were collected from the upper part of the crowns. The percentage of infected leaves as well as the reduction of carbon assimilation capacity was assessed. Furthermore, we evaluated the average reduction of carbon assimilation capacity and the percentage of withering branch tips in 25 adjacent trees. Incidences of powdery mildew were observed in seven out of the ten stands. The maximum tree damage did not exceed 22% leaf infection and mean defoliation within the study areas ranged from 18% to 61.4%. Non-withering branch tips were observed in one post-flood area as well as in one area situated outside the flooded region. Within the remaining areas studied, the average proportion of withering branch tips ranged from 0.4% to 13.8%. Statistical analyses showed that differences between the investigated stands with regard to the rate of powdery mildew occurrence were not significant. Correlating the means, however, revealed a relationship between powdery mildew incidence and branch tip withering. This relationship is a possible indication of the ongoing oak dieback. No statistically significant relationship between tree defoliation and powdery mildew incidence was found. The lack of statistical significance, as observed here, implies that water stagnation within the investigated stands had no effect on Erysiphe alphitoides infection.

Spatial variability of spruce budworm defoliation at different scales

Aerial survey records of defoliation by spruce budworm (Choristoneura fumiferana (Clem.)) in New Brunswick, Canada taken annually from 1965 to 1992, were analyzed at four scales (66×66km, 10×10km, 2×2km, 1×1km) to determine patterns and spatial variability of defoliation. Spruce budworm defoliated 92% of the 7.4 million ha study area in at least one year. Cluster analysis was used to group similar defoliation patterns, and 51% of the variation in the 28-year record was described by 28 representative defoliation patterns, at 1×1km cell size. Individual defoliation patterns were grouped into five spruce budworm outbreak classes (termed A–E), which each covered 12–27% of the area. These differed substantially in defoliation duration and severity: classes A–B had only 1–3years of moderate–severe defoliation and 42–75% cumulative defoliation; class C had 8years and 127% cumulative defoliation; and classes D–E had 13–16years and 170–208% cumulative defoliation. Given the degree of ‘averaging out’ of high defoliation occurrences that cause the largest impacts, larger 10×10km and 66×66km cells were inappropriate for impact analysis. Defoliation variability was highest at 20–60% mean defoliation than at lower or higher defoliation levels. Distributions of area in each class in 1×1km cells for 66×66km areas throughout the province showed that with the exception of several small coastal areas, four or five of the above outbreak classes occurred in all areas. The wide variation in spruce budworm outbreak patterns is important in making management decisions that differentiate insecticide or salvage treatments based on defoliation severity, and emphasizes the importance of accurate annual aerial survey or remote sensing-based defoliation assessment.

Forest Condition in Europe: 2013 technical report of ICP Forests. Report under the UNECE Convention on Long-Range Transboundary Air Pollution (CLRTAP)

Of the 42 countries that have participated in ICP Forests since 1986, 27 countries reported largescale monitoring data from Level I plots and more detailed forest ecosystem related monitoring data from Level II plots for the year 2012. In total, the participating countries provided information on more than 15,000 plots and more than 220,000 trees. Data analyses for this 2013 Technical Report focused on the impact of air pollution on tree crown condition and on sulphate and nitrogen deposition to forests. In addition, the impact on individual trees of factors other than air pollution, e.g., biotic agents, was assessed. Crown condition is the most widely applied indicator for forest health and vitality of European forests. One of its primary parameters is the rate of defoliation, which is assessed as the percentage of needle/leaf loss in the crown compared to a reference tree with full foliage. The mean defoliation of 114,361 sample trees on 6,168 transnational Level I plots in 2012 was 19.7%. Of all trees assessed in 2012 every fourth to fifth tree (22.9%) was scored as damaged, i.e., had a defoliation rate of more than 25%. In general, broadleaved trees showed a higher mean defoliation rate than conifer species (23.6% and 20.2%, respectively). Oak species still seem to be the most vulnerable of all the investigated species. Of the main species groups, deciduous temperate oak species had the highest mean defoliation (26.5%), closely followed by Mediterranean evergreen oak species (25.2%), and deciduous (sub-) temperate oak species (24.6%). A mean defoliation rate of 19.6% was assessed for European beech (Fagus sylvatica). Coniferous species expressed lower defoliation rates on average, with European spruce (Picea abies) reaching 19.2%, followed by Scots pine (Pinus sylvestris) with 19.3%, and Mediterranean lowland pine species with 20.7%. These figures are, however, not directly comparable to those of previous reports because of fluctuations in the plot sample that are primarily due to changes in the annual participation of countries. Therefore, the temporal development of crown condition was calculated separately from the monitoring results for those countries which have submitted data every year without interruption since 1993, 1998, and 2002, respectively. In addition, maps were drawn that depict temporal species trends in defoliation. The presented results suggest that there was no overall improvement of crown condition for the longest analyzed time period from 1993 to 2012. Over the last 20 years the percentage of plots with clearly increasing mean defoliation (17.2%) even exceeded the share of plots with decreasing defoliation (12.5%) but most of the investigated plots showed no statistically significant change in crown condition (70.3%). Compared to the previous year only, the investigated trees showed on average similar rates of defoliation in 2012. More than three out of four plots (78.7%) showed no statistically significant difference in mean defoliation between those two years. Defoliation increased on 13.8% and decreased on only 7.5% of the plots.

Effect of Air Pollution on the Health Status of Spruce Stands

This paper presents the results of research on local air pollution (nitrogen and sulfur concentrations) and on the changes in the health status of trees observed in spruce stands in the period 1980–2011 in the Krkonose Mountains National Park. Data on precipitation and sulfur and nitrogen deposition were collected in regular 2-week intervals from 1994 to 2010. Precipitation was measured at 5 monitoring stations; the health status of forest stands was evaluated on 6 research plots located in stands dominated by Norway spruce (Picea abies [L.] Karst) in zones where there has been a significant threat from air pollution since 1980. The health status of spruce stands was assessed on the basis of the degree of defoliation, classified into 6 levels. In all localities since 1994, the total deposition of sulfates decreased significantly, from 50–80 kg ha−1 year−1 to 8–13 kg ha−1 year−1; however, no clear trend in the development of nitrogen deposition could be stated. The mean defoliation of living and all trees ...

Long term losses caused by foliar diseases on growth and survival of Eucalyptus globulus in Uruguay

Eucalyptus globulus is the most important forest species in Uruguay, with more than 250,000 ha of commercial plantations. Despite its high susceptibility to diseases, production losses caused by foliar diseases have not been properly quantified in this country. This study analyzes the effects of foliar damage on growth and survival using data from a progeny test of E. globulus naturally infected by Teratosphaeria leaf disease and eucalypt rust (Puccinia psidii). The severity of leaf spots and defoliation were quantified 8 months after planting and tree growth and mortality were evaluated 2, 4 and 6 years later. The trial had a high incidence of foliar damage, with a mean leaf spot severity of 28.7% and a mean defoliation of 37%. The greatest impact of foliar damage, both on growth rate and mortality, occurred in the first 2 years after damage was assessed. During this period, leaf spot severity less than 40% and defoliation below 50% did not affect growth, while survival was affected when leaf damage was 70% or greater. By the sixth year both stem growth and survival were affected by severe foliar damage (spotting or defoliation of 80% or more), with a loss of up to 25% in diameter and an accumulated mortality over 70%. It has been established for the first time that under the intensive Uruguayan productive conditions, E. globulus trees can tolerate a relatively high degree of leaf spotting or defoliation but severe foliar damage in the first months can cause considerable production losses, putting at risk the economical viability of this species.

First results of a nation-wide systematic forest condition survey in Turkey

Abstract: Monitoring of forest condition in Turkey started in 2006 when a 16x16 km grid of Level I plots was established. In 2007, the first 48 Pinus brutia plots were surveyed for crown condition. In 2008 and 2009, the plots were 398 and 563, respectively. In 2007, the mean defoliation for P. brutia was 13.0 %. In 2008-2009, the mean defoliation was 19.5-19.8 % and 27.0-23.0 % for coniferous and broadleaved species, respectively. Defoliation was higher than 25 % on 24.6-18.7 % of the monitored trees. The species with the highest defoliation were Carpinus betulus and Juniperus foetidissima in 2008, and Quercus pubescens and Juniperus communis in 2009. The slight improvement in forest health in 2009 may be attributed to better weather conditions than in 2008 (higher precipitation). The forests along the Black Sea coast of Thrace showed the highest defoliation in both 2008 and 2009. This may be due to transboundary air pollution from Istanbul, where sources of sulphate and nitrate pollution occur. Elevated defoliation rates were also observed in the Black Sea region; they were most probably caused by biotic factors in plots subject to industrial pollution.

Effects of defoliation by Eucalyptus weevil, Gonipterus scutellatus, and chrysomelid beetles on growth of Eucalyptus globulus in southwestern Australia

Plantations of Eucalyptus globulus in southwestern Australia are defoliated by Eucalyptus weevil, Gonipterus scutellatus, and a complex of chrysomelid and scarab beetles, yet there is no information on the impact of beetle defoliation to tree growth in southwestern Australia. To address this shortcoming, we used insect exclusion trials, to compare growth of insecticide treated (and thus relatively undamaged) trees with untreated (and thus defoliated) trees to determine whether defoliation by G. scutellatus and other beetles reduced the growth and harvest volume of E. globulus trees. Our results showed some evidence of beetle defoliation reducing growth of E. globulus. Mean defoliation levels of the growing tip of untreated trees ranged from 18% to 33% across the duration of the study and were significantly greater than mean defoliation levels of 5–16% on insecticide treated trees. Seasonal peaks in defoliation of 30–80% to the growing tip of untreated trees were recorded between late spring and early autumn. The greatest impact of defoliation on tree growth was evident during the 2.5 year period of insect exclusion, when higher relative growth rates were recorded for insecticide treated trees, which were significantly different from relative growth rates of untreated trees at two of the four plantations. However, our results showed only a limited impact of beetle defoliation on the total volume at harvest. Initially small trees tended to suffer more severe defoliation than initially large trees. Effects of insect exclusion treatment on harvest volume were modified by the initial tree size and the relationship between the initial tree size and levels of defoliation.

Insect defoliation of mixed-species eucalypts in East Gippsland

Summary Ground surveys were conducted in the coastal and inland mixed—species eucalypt forests of East Gippsland from 2003 to 2006, using ten permanent forest health assessment sites across the region, to determine the cause, extent and severity of extensive defoliation first observed in late 2003. The primary cause of defoliation in the 2003 and 2005 outbreaks were Doratifera spp. (cup moth) and Uraba lugens (gumleaf skeletoniser) respectively. Eucalyptus globoidea (white stringybark) and E. elata (river peppermint) appeared most susceptible while E. cypellocarpa (mountain grey gum), E. obliqua (messmate) and E. sieberi (silvertop) were generally more resistant to defoliation by these insect species. The initial assessment in November 2003 indicated high levels of defoliation with a mean of 71% (range: 30–85%) across all ten sites. Re-assessment of the sites in March 2004 indicated active defoliation had ceased and that foliage cover in the trees had improved with mean defoliation of 34% (range: 15–60%), an improvement of 37%. Subsequent defoliation late in 2005 was not as severe as the 2003 outbreak, with mean defoliation in November 2005 being 23% (range: 10–40%) across all ten sites. Re-assessment in March 2006 indicated that active defoliation had ceased and that levels of foliage cover in the trees had increased over the 2005–2006 summer, with mean defoliation of 17% (range: 10–30%) recorded, an improvement of 6%. Rather than being considered as one continuous outbreak by a single pest species, the two defoliation episodes should be regarded as separate events caused by separate insect species, although their cause(s) may have foundation in similar conditions. The U. lugens outbreak can be reliably linked to low rainfall in the region. The cause of the outbreaks by Doratifera spp. is uncertain because of insufficient knowledge concerning their lifecycle. While climatic factors are likely triggers, other factors such as eucalypt host susceptibility, foliage nutritional status, altitude, forest type, soils and geology may also influence the occurrence of Doratifera spp. outbreaks. Further, it still has to be determined whether the factors that trigger outbreaks affect Doratifera spp. directly or reduce parasitoid/predator populations that usually keep Doratifera spp. populations in check. As little is known of the predisposing factors for outbreaks (especially for Doratifera spp.), the appropriate nature and timing of any potential control measures are difficult to identify. Continued monitoring of all potential damaging insect pest populations and associated canopy cover is recommended as part of a structured forest health surveillance system in order to predict outbreaks and allow appropriate contingency plans to be made if required. However, as most native insect outbreaks in native forests are short term and part of the normal forest ecosystem, the implementation of control measures is usually not required. The potential for long-term effects of drought to increase outbreak frequency and subsequently affect tree growth and health should not be discounted, thus emphasising the need for regular monitoring.

Comparison of Virginia-Type Peanut Cultivars and Interspecific Hybrid Derived Breeding Lines for Leaf Spot Resistance, Yield, and Grade

AbstractDisease resistant cultivars with good quality are needed by U.S. peanut growers to lower production costs. In the Virginia-Carolina (V-C) production area, use of resistant cultivars to reduce leaf spots would be a cost-effective and environmentally safe alternative to chemical applications. Twenty-six interspecific hybrid derived breeding lines with 5 Arachis species in their pedigrees, six resistant A. hypogaea checks and 11 susceptible cultivars were evaluated for leaf spot resistance in field tests at the Peanut Belt Research Station in Lewiston, NC from 2004 to 2006 without leaf spot fungicides. Defoliation was rated on a 1–9 proportional scale with 1 = no defoliation (resistant) and a 9 = complete defoliation (susceptible). The mean defoliation score of the cultivars was 6.8±0.1 (range = 6.4 to 7.4), compared to 5.3±0.1 (range = 4.4 to 6.3) for the interspecific hybrid derived breeding lines. Some of the interspecific hybrid derived breeding lines showed levels of leaf spot resistance similar to the resistant A. hypogaea checks (mean = 4.3±0.2), suggesting that these breeding lines contain genes conditioning resistance to the leaf spots. The combined mean yield of the cultivars was 2709±103 kg/ha (range = 2296 kg/ha to 3070 kg/ha), whereas that of the interspecific hybrid derived breeding lines was 3169±119 kg/ha (range = 2467 kg/ha to 3767 kg/ha). Evaluation of selected grade characteristics showed that several interspecific hybrid derived breeding lines have grade similar to those of the commercial cultivars. Sixteen of the 26 interspecific hybrid derived breeding lines with five different diploid species in their pedigrees and NC 7, the commercial flavor standard for the V-C area, were also evaluated for sensory quality. No significant variation among test entries was found for the roasted peanut, sweet, or bitter sensory attributes. This suggests that high levels of leaf spot resistance can be combined with superior yield, grade and other quality factors and that some of these lines may become useful for commercial production in the V-C area.

Comparative Canopy Damage among Provenances of Baldcypress Associated with the Presence of Cercosporidium sequoiae (Ellis and Everth.) W.A. Baker and Partridge

Seeds of Taxodium distichum (L.) Rich. were collected, germinated, and grown from native stands ranging from Mexico, Texas, Louisiana, Mississippi, and Alabama. Twenty-two provenance selections were planted in Summer 2004 in College Station, TX, in 36 replicated single-plant replications per block for a total of 792 trees. Below-average midsummer temperatures and above-average number of rainfall events were conducive to the development of a leaf blight associated with the presence of Cercosporidium sequoiae (Ellis and Everh.) W.A. Baker and Partridge. A survey conducted in Oct. 2007 rated differential defoliation responses among provenances. Selections of Taxodium distichum var. mexicanum (Gordon) from Mexico and south Texas showed defoliation rates from 89% to 96%, whereas T. distichum var. distichum from central Texas had defoliation ratings from 79% to 99%. With the exception of one family collected from the Sabinal River in Texas, the central Texas selections had similar defoliation compared with those from south Texas. Selections of T. distichum var. distichum and one selection of T. distichum var. imbricarium (Nutt.) Croom from southeastern regions (Alabama, Louisiana, Mississippi, and east Texas) showed greater tolerance to the presence of the leaf blight with 52% to 80% mean defoliation. A few individuals within these families exhibited little or no symptoms of the leaf blight. In general, those selections from high-rainfall, high-humidity areas had less defoliation associated with the presence of the leaf blight fungus, although defoliation was variable among provenances within all geographical regions. These results suggest that tolerance to defoliation from C. sequoiae could be included in selection criteria when choosing possible germplasm releases from Taxodium distichum.

Effects of surrounding forest and site conditions on growth reduction of balsam fir and spruce caused by spruce budworm defoliation

The species composition of surrounding forest and site characteristics have been postulated to influence growth loss caused by eastern spruce budworm (Choristoneura fumiferana Clem.) defoliation. Forty spruce (Picea spp.) and balsam fir (Abies balsamea (L.) Mill.) stands located in north-central New Brunswick, Canada, were measured for defoliation and tree growth and used to determine the effects of surrounding forest (softwood, mixedwood), site (wet soil – nutrient poor; moist soil – nutrient rich), and species group (balsam fir, spruce) on growth reduction caused by spruce budworm. Stem analysis of six trees per stand (total 240 trees) determined mean specific volume increment (SVI) per year in 1973–1993. There was relatively little defoliation during the 1989–1993 measurement period, and regression analyses showed that SVI was significantly (p = 0.0299) related to mean defoliation for only one of eight treatment classes: balsam fir on moist–rich sites in mixedwood forests. However, two periods of earlier growth reduction were evident, and analysis of variance showed that balsam fir on wet–poor sites sustained 12% greater (p = 0.0071) reduction in SVI from 1987 to 1990 than balsam fir on moist–rich sites. White spruce (Picea glauca (Moench) Voss) sustained 13% greater (p = 0.0198) reduction in SVI from 1973 to 1978 than red spruce (Picea rubens Sarg.) – black spruce (Picea mariana (Mill.) BSP). Surrounding forest type did not significantly affect SVI reduction from 1973 to 1978 or from 1987 to 1990, but from 1973 to 1978 stands in softwood forest sustained 5%–8% more growth reduction than those in mixedwood forest.

Variation among provenances and families of blackbutt (Eucalyptus pilularis) in early growth and susceptibility to damage from leaf spot fungi

Growth to 38 months and severity of Mycosphaerella leaf disease and target spot (caused by Aulographina eucalypti (Cooke & Mass.) von Arx & Muller) were assessed in a Eucalyptus pilularis Smith (blackbutt) family trial in New South Wales (NSW), Australia. Significant variation in growth, disease, and defoliation was found among the 40 provenances and 321 families tested; however, relatively few provenances had concentrations of superior or poor families. Most families in three higher altitude NSW provenances were superior for volume increment, while three southeast Queensland provenances had low mean volume increment. Mycosphaerella damage and defoliation tended to be low in several higher altitude northern NSW provenances, but the southeast Queensland provenances had significantly higher mean defoliation. Individual narrow sense heritability estimates were low to moderate for Mycosphaerella damage (0.38) and defoliation (0.22) and low for Aulographina damage (0.13) and volume increment (0.13). Significant genetic and phenotypic correlations between Mycosphaerella damage and defoliation were low and positive. Low to moderate negative correlations occurred between Mycosphaerella damage and volume increment and between defoliation and volume increment, suggesting that Mycosphaerella leaf disease, in particular, and defoliation had deleterious effects on tree growth. However, the impact of these foliar pathogens on the volume of E. pilularis is often low, so selecting for growth and form alone in the early stages of domestication could provide acceptable gains in yield.

Experimental aerial application of a new isolate of the nucleopolyhedrovirus, CfMNPV against choristoneura fumiferana (Lepidoptera: Tortricidae)

A new isolate of spruce budworm ( Choristoneura fumiferana) multicapsid nucleopolyhedrovirus called Tortrivirus and designated CfMNPV-T3 was field tested in 1998–1999 to evaluate its efficacy against C. fumiferana. A double application of the virus was sprayed aerially at 5.0×10 11 occlusion bodies in 2.5 l of diluent carrier per hectare. Following the application in 1998, viral infection of spruce budworm larvae increased significantly but there were no linear relationships between spray deposit, larval infection and insect population reduction and no epizootic was initiated. As a consequence, larval infection reverted to incipient levels in 1999. Spruce budworm population reductions that could be attributed to the virus were <10% and mean defoliation in the virus-treated plots exceeded 50% in both years. These findings indicate that CfMNPV-T3 was not therefore, as effective in controlling C. fumiferana populations as laboratory studies had suggested it would be.